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Oyster mushroom cultivation on cereal and legume straw of poor feed quality

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  • Received: 31 May 2024
    Revised: 05 July 2024
    Accepted: 09 July 2024
    Published online: 12 August 2024
    Studies in Fungi  9 Article number: e010 (2024)  |  Cite this article
  • This study explores the viability of cultivating oyster mushrooms on cereal and legume straw of poor feed quality, investigating oyster mushroom productivity, and the implications for mass-, nitrogen- and carbon flows within the agricultural system. Four types of straw (wheat, maize, faba bean, and soy bean) were utilized as substrates for mushroom cultivation. Fresh yields varied widely, from 114% biological efficiency on maize straw to 58% on wheat straw, while dry yields ranged from 9.2% biomass conversion rate on maize straw to 3.8% on wheat straw. The protein content of mushrooms varied between 16.8% on wheat straw and 23.2% on faba bean straw, correlating with the nitrogen content of the straw. Furthermore, results revealed significant variations in carbon emissions, ranging from an estimated 3.5 kg (on wheat straw) to 2.6 kg (on soy straw) emitted per kg of dry mushroom produced. These findings underscore the importance of substrate selection in mushroom cultivation, with implications for agricultural resource management and food production. Depending on the focus, different substrates may be considered as optimal. While maize straw produced most mushrooms in this study, soy bean straw emitted the least carbon in relation to yield, faba bean straw produced mushrooms with higher protein content, and wheat straw retained the most nitrogen in the spent mushroom substrate.
  • Bletilla Rchb. f. is one of the most economically valuable groups of orchids in the world. Due to its ornamental significance, the genus Bletilla occupies an important place in the worldwide horticultural market. Furthermore, in China, Japan, South Korea, and other Asian countries, it is highly valued for its medicinal use[1].

    There are eight species in the genus Bletilla, including Bletilla chartacea (King & Pantl.) Tang & F.T. Wang, Bletilla cotoensis Schltr., Bletilla foliosa (King & Pantl.) Tang & F.T. Wang, Bletilla formosana Schltr., Bletilla guizhouensis J. Huang & G.Z. Chen, Bletilla morrisonensis Schltr., Bletilla ochracea Schltr., and Bletilla striata Rchb.f.[2,3]. The distribution area spans from northern Myanmar in Asia to Japan via China[4]. Five species are native to China, namely, B. foliosa, B. formosana, B. guizhouensis, B. ochracea, and B. striata. In China, people have assigned various names to Bletilla based on its morphology and efficacy, such as baiji (白及/白芨), baigen (白根), baige (白给), baijier (白鸡儿), baijiwa (白鸡娃), diluosi (地螺丝), gangen (甘根), junkouyao (皲口药), lianjicao (连及草), and yangjiaoqi (羊角七)[5]. These diverse appellations highlight the importance of this genus in Chinese folk biological culture.

    The medicinal material known as 'baiji' in traditional Chinese medicine (TCM) is usually the dried tuber of B. striata, which is also the authentic product included in the Chinese Pharmacopoeia[6]. According to the Chinese Pharmacopoeia (2020), TCM baiji is sliced, dried, and crushed into a powder that can be used topically or internally, with a recommended dosage of 3–6 g at a time, offering astringent, hemostatic, detumescence, and myogenic effects. It is often used for conditions such as hemoptysis, hematemesis, traumatic bleeding, sores, and skin chaps[7]. Although only B. striata is the authentic product of TCM baiji, the other four Bletilla species native to China are also used as substitutes, and this practice is widespread[8].

    Modern research indicates that Bletilla contains a variety of chemical components, including benzol, dihydrophenanthrene, phenanthrene, and quinone derivatives. These components confer pharmacological effects on Bletilla, such as hemostasis, anti-tumor activity, and promotion of cell growth[9]. Due to its outstanding medicinal value, Bletilla can be found in nearly every corner of the traditional medicine market (Fig. 1). However, habitat destruction and uncontrolled mining have led to a significant reduction in the native populations of Bletilla, making its protection an urgent priority. Therefore, this paper provides a comprehensive review of relevant research up to August 2023, covering botanical characteristics, resource distribution, ethnobotanical uses, chemical components, pharmacological effects, clinical applications, and safety evaluations of Bletilla. The aim is to raise awareness and promote the protection and sustainable use of this genus.

    Figure 1.  Varieties of Bletilla at the traditional March Medicinal Market in Dali, Yunnan, China.

    The morphology of different Bletilla species is highly similar. The primary taxonomic feature distinguishing each species is the characteristics of the flower, particularly the lip of the flower, including its size, shape, and the number and shape of longitudinal ridges on the lip plate (Table 1, Fig. 2)[1014].

    Table 1.  The morphological differences among five species of Bletilla plants native to China.
    Morphological featureBletilla striataBletilla formosanaBletilla ochraceaBletilla foliosaBletilla guizhouensis
    Plant height (cm)18−6015−8025−5515−2045−60
    Rhizome shapeCompressedCompressedSomewhat compressedSubgloboseCompressed
    Rhizome diameter (cm)1−31−2About 21−1.53−4
    Stem characteristicsStoutEnclosed by sheathsStoutStout, shortThin
    Leaf shapeNarrowly oblongLinear-lanceolateOblong-lanceolateElliptic-lanceolateNarrowly lanceolate
    Leaf size (cm)8−29 × 1.5−46−40 × 0.5−4.58−35 × 1.5−2.85−12 × 0.8−325−45 × 1.2−4.5
    Flower colorPurplish red or pinkPale purple or pinkYellowPale purpleDeep purple
    Flower sizeLargeMediumMediumSmall to mediumLarge
    Inflorescence structureBranched or simpleBranched or simpleSimpleSimpleBranched
    Pedicel and ovary length (mm)10−248−12About 187−913−17
    Sepal shapeNarrowly oblongLanceolateLanceolateLinear-lanceolateOblong-elliptic
    Petal shapeSlightly larger than sepalsSlightly narrower than sepalsObliqueLanceolateOblong-elliptic
    Lip shapeObovate-ellipticBroadly ellipticNarrowly rhombic-obovateNarrowly oblongNarrowly oblong
    Lip colorWhite with purplish veinsWhitish to pale yellow with small dark purple spotsWhitish to pale yellow with small dark purple spotsWhite with purplish spots and purple edgeWhite with deep purple edge
    Number of lip Lamellae5 lamellae5 undulate lamellae5 longitudinal lamellae3 fimbriate lamellae7 longitudinal lamellae
    Column characteristicsSubterete, dilated towards apexSubterete, dilated towards apexSlender, dilated towards apexCylindric, dilated towards apexSuberect, with narrow wings
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    Figure 2.  (a)−(d) Bletilla striata (Thunb. ex Murray) Rchb. f. (e)−(h) Bletilla formosana (Hayata) Schltr. (i)−(l) Bletilla ochracea Schltr. (m), (n) Bletilla sinensis (Rolf) Schltr. (o), (p) Bletilla guizhouensis Jie Huang & G.Z. Chen (Photographed by Wang Meina, Zhu Xinxin, and He Songhua).

    The flowers of B. striata are large and purplish-red or pink, with narrowly oblong sepals and petals measuring 25−30 mm in length and 6−8 mm in width. They have acute apices, nearly as long as the sepals and petals. The lip is obovate or elliptic, predominantly white with purplish-red coloration and purple veins, measuring 23−28 mm in length, slightly shorter than the sepals and petals. The lip disc exhibits five longitudinal folds extending from the base to near the apex of the middle lobe, with waviness occurring only above the middle lobe[11]. In China, B. striata is found in regions such as Anhui, Fujian, Guangdong, Guangxi, Gansu, Guizhou, Hubei, Hunan, Jiangsu, Jiangxi, Shaanxi, Sichuan, and Zhejiang. It also occurs in the Korean Peninsula and Japan, thriving in evergreen broad-leaved forests, coniferous forests, roadside grassy areas, or rock crevices, at altitudes ranging from 100−3,200 m[12].

    B. ochracea's flowers are medium to large, featuring yellow or yellow-green exteriors on the sepals and petals, while the insides are yellow-white, occasionally nearly white. The sepals and petals are nearly equal in length, oblong, measuring 18−23 mm long and 5−7 mm wide, with obtuse or slightly pointed apices, often adorned with fine purple spots on the reverse side. The lip is elliptic, typically white or light yellow, measuring 15−20 mm in length and 8−12 mm in width, with three lobes above the middle. The lip disc is characterized by five longitudinally ridged pleats, with undulations primarily occurring above the middle lobe[13]. B. ochracea is native to southeastern Gansu, southern Shaanxi, Henan, Hubei, Hunan, Guangxi, Guizhou, Sichuan, and Yunnan, thriving in evergreen broad-leaved forests, coniferous forests, or beneath shrubs, in grassy areas or alongside ditches at altitudes ranging from 300−2,350 m[14].

    B. formosana's flowers come in shades of lavender or pink, occasionally white, and are relatively small. The sepals and petals are narrowly oblong, measuring 15−21 mm in length and 4−6.5 mm in width, and are nearly equal in size. The sepals have subacute apices, while the petal apices are slightly obtuse. The lip is elliptic, measuring 15−18 mm in length and 8−9 mm in width, with three lobes above the middle. The lip disc exhibits five longitudinal ridge-like pleats, which are wavy from the base to the top of the middle lobe[15]. B. formosana is indigenous to southern Shaanxi, southeastern Gansu, Jiangxi, Taiwan, Guangxi, Sichuan, Guizhou, central to northwest Yunnan, southeast Tibet (Chayu), and Japan. It is typically found in evergreen broad-leaved forests, coniferous forests, road verges, valley grasslands, grassy slopes, and rock crevices, at altitudes ranging from 600−3,100 m[16].

    The flowers of B. foliosa are small and lavender, with white sepals and petals featuring purple apices. The sepals are linear-lanceolate, measuring 11−13 mm in length and 3 mm in width, with subacute apices. The petals are lanceolate, also measuring 11−13 mm in length and 3 mm in width, with acute apices. The lip is white, oblong, adorned with fine spots, and features a purple apex. It measures 11−13 mm in length and 5−6 mm in width, tapering near the base and forming a scaphoid shape. The lip is anteriorly attenuated, unlobed, or abruptly narrowing with inconspicuous three lobes and exhibits fringe-like fine serrations along the edge. Three longitudinal ridge-like pleats are present on the upper lip disc[17]. B. foliosa typically grows on hillside forests, with its type specimen collected from Mengzi City, Honghe Hani and Yi Autonomous Prefecture, Yunnan Province, China[17].

    B. guizhouensis is a recently discovered species in Guizhou, China. In terms of shape, B. guizhouensis closely resembles B. striata, but it can be distinguished by its ovate-oblong buds, oblong dorsal sepals, obovate lips, and middle lobes of the lips, which are oval in shape. The disc of B. guizhouensis features seven distinct longitudinal lamellae, setting it apart from other known Bletilla species and establishing it as a distinct species[2]. Presently, B. guizhouensis has only been found in Guizhou, China, primarily thriving in evergreen broad-leaved forests at altitudes ranging from 900−1,200 m[3].

    Understanding the morphology, habitat, and distribution of Bletilla species is crucial for the conservation and propagation of these resources. To effectively implement plant conservation and breeding programs, a comprehensive understanding of the specific morphological characteristics, growth environments, and native habitats of these plants is essential, as without this knowledge, effective results cannot be achieved.

    The ethnobotanical uses of Bletilla worldwide primarily fall into two categories: ornamental and medicinal purposes. Bletilla orchids, renowned for their striking and distinct flowers, are commonly cultivated for ornamental purposes across many countries[18]. Valued for their aesthetic appeal, these orchids are frequently grown in gardens and utilized as potted plants. Among the various cultivars, B. striata stands out as the most favored choice for ornamental horticulture due to its ease of cultivation and adaptability to diverse climates[19,20].

    Contrastingly, in select Asian countries, Bletilla assumes a crucial role as a medicinal plant. For instance, influenced by TCM, the tuber of Bletilla also serves as a crude drug for hemostatic and anti-swelling purposes in Japan[21]. Likewise, traditional Korean medicine, deeply rooted in TCM principles, extensively documents the versatile use of Bletilla in addressing issues such as alimentary canal mucosal damage, ulcers, bleeding, bruises, and burns[22]. In Vietnam, Bletilla has been used as a medicinal herb for treating tumors and skin fissures, aligning with practices observed in the ethnic communities of southwest China[23].

    In China, Bletilla boasts a longstanding medicinal history, with numerous classical ancient Chinese medicine books containing detailed records of its medicinal applications[2432]. Even in contemporary society, many ethnic groups residing in mountainous areas in China continue to uphold the traditional medical practice of using Bletilla medicinally[31].

    In ancient Chinese medical literature, detailed records of Bletilla's morphology can be traced back to the late Han Dynasty, around 200 AD[24]. The Mingyi Bielu, a historical source, documented, 'Bletilla grows in the valley, with leaves resembling those of Veratrum nigrum L., and its root is white and interconnected. The ideal time for harvesting is September'. As awareness of the medicinal significance of Bletilla grew, successive dynastic-era Chinese medical texts consistently included descriptions of Bletilla's morphology (Table 2). In the Ming Dynasty, Li Shizhen compiled these earlier accounts of Bletilla's plant characteristics in his work, the Compendium of Materia Medica. He even provided an illustrative depiction of this plant genus (Fig. 3)[25].

    Table 2.  Morphological description of the plants belonging to Bletilla in the ancientChinese medicinal books.
    Dynasty (Year)TitleAuthorOriginal ChineseEnglish translation
    Late Han
    (184−220 AD)
    Mingyi Bielu/白给生山谷, 叶如藜芦,
    根白相连, 九月采
    Bletilla grows in the valley, with leaves like Veratrum nigrum L., root is white and connected. September is the time for harvesting.
    Wei-Jin period
    (220−420 AD)
    WuPu BencaoWu Pu白根, 茎叶如生姜, 藜芦,
    十月花, 直上, 紫赤色,
    根白连, 二月, 八月, 九月采
    Bletilla, stems and leaves like Zingiber officinale Roscoe and V. nigrum. It blooms in October and is purple and red, the inflorescence is vertical and upward. The roots are white and connected. It can be dug in February, August, and September.
    the Northern and Southern
    (420−589 AD)
    Bencao JizhuTao Hongjing近道处处有之, 叶似杜若,
    根形似菱米, 节间有毛
    It is everywhere near the road. The leaves are like Pollia japonica Thunb. The roots are like the fruit of Trapa natans L., and internode are many fibrous roots.
    Tang
    (618−907 AD)
    Su Jing, Zhangsun Wuji, etcTang materia medica生山谷, 如藜芦, 根白连, 九月采Born in the valley, with leaves like V. nigrum, root is white and connected. September is the time for harvesting.
    Song
    (960−1279 AD)
    Su SongCommentaries on the Illustrations白芨, 生石山上。春生苗,
    长一尺许, 似栟榈及藜芦,
    茎端生一台, 叶两指大, 青色,
    夏开花紫, 七月结实, 至熟黄黑色。
    至冬叶凋。根似菱米, 有三角白色, 角端生芽。二月, 七月采根
    Bletilla grow on the stone hill. It sprouts in spring and grows about a foot long. The seedlings are like Trachycarpus fortunei (Hook.) H. Wendl. and V. nigrum. The leaves are two finger-size. In summer, it blooms purple flowers and bears fruit in July. The ripe fruit is yellow-black. The leaves wither in winter. The root is like the fruit of T. natans, with three corners, white, and sprouting at the corners. The roots are dug in February and July.
    Ming
    (1368−1644 AD)
    Li ShizhenCompendium of Materia Medica一棵只抽一茎, 开花长寸许,
    红紫色, 中心如舌, 其根如菱米,
    有脐, 如凫茈之脐,
    又如扁扁螺旋纹, 性难干
    Only one stem per herb. The flower is more than one inch long, red and purple, and the center resembles a tongue. Its root is similar to the fruit of T. natans, possessing an umbilicus akin to that of Eleocharis dulcis (N. L. Burman) Trinius ex Henschel. It has spiral veins and is challenging to dry.
    −, Anonymous.
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    Figure 3.  Bletilla in Compendium of Materia Medica.

    Generally, ancient Chinese medical texts did not make clear distinctions between different Bletilla species. They collectively referred to plants with similar morphological traits as 'baige', 'baigen', 'baiji', 'gangen', 'lianjicao', or 'ruolan'. However, through textual analysis, it has been established that the descriptions of Bletilla in ancient texts before the Ming Dynasty largely align with Bletilla striata in terms of plant height, pseudo-bulb shape, leaf morphology, flower and fruit colors, and other characteristics. While the Bletilla portrayed in attached images may not precisely match B. striata in terms of morphology, considering the textual descriptions, it generally corresponds with B. striata. In writings from the Ming Dynasty and later periods, more specific descriptions of Bletilla emerged, encompassing details about its vascular arrangement, inflorescence, and flower structure, which consistently align with B. striata. Consequently, researchers have corroborated that the original plant of Bletilla described in ancient texts is Bletilla striata[24,33].

    According to the ancient Chinese medicinal books, Bletilla was used to treat a wide variety of conditions, including coughing, bruising, and bleeding, but their most mentioned use in ancient Chinese texts is for skin whitening and freckle removal[25]. Since ancient times, Bletilla species have been used consistently for skin care and whitening, and there are many well-known skincare products related to Bletilla. These Chinese formulae with Bletilla are similar to modern facial masks, face creams, facial cleanser, hand creams and other skin care products[26].

    For example, a prescription for 'facial fat (面脂)' in Medical Secrets from the Royal Library (752 AD) is made by boiling Bletilla with other traditional ingredients, and is applied to the face, resulting in skin whitening, freckle and wrinkle removal[27]. The 'Angelica dahurica cream (白芷膏)' in the General Medical Collection of Royal Benevolence (1111−1125 AD) is reputed to whiten facial skin through a seven-day treatment regiment, and contains Bletilla as the main botanical ingredient along with Angelica dahurica[28]. Jingyue Quanshu (1563-1640 AD) also contains a prescription called 'Yurong powder (玉容散)' for facial skin care. 'Yurong powder' is made of a fine powder of Bletilla, Nardostachys jatamansi (D. Don) DC., Anthoxanthum nitens (Weber) Y. Schouten & Veldkamp and other herbs[29]. Washing the face with Yurong powder in the morning and evening every day is said to make a person's face white without blemishes (Fig. 4)[29].

    Figure 4.  Yurong powder made of Bletilla and other traditional Chinese medicines in Jingyue Quanshu.

    In addition, in ancient Chinese medicine texts, Bletilla is also a well-known medicine for treating hematemesis, hemoptysis and bruises[23]. According to Shennong's Classic of Materia Medica (25−220), grinding the white fungus into fine powder and taking it after mixing with rice soup can be effective for treating lung damage and hematemesis[30]. Among the Prescriptions for Universal Relief (1406), 18 traditional Chinese medicines, such as Bletilla, are used to make 'snake with raw meat cream', which is said to be useful to treat carbuncles and incised wounds[31]. There is also a record of Bletilla powder treating lung heat and hematemesis in the Collected Statements on the Herbal Foundation (1624)[32].

    In ancient Chinese medicinal texts, most Bletilla are said to be useful for lung injury and hemoptysis, epistaxis, metal-inflicted wounds, carbuncles, burns, chapped hands and feet, whitening and especially for skin care. In the ancient medicinal texts, Bletilla is used alone or mixed with other traditional Chinese medicines. It is usually used in the form of a powder. The various medicinal effects of Bletilla described in these ancient texts suggest the great potential of this genus in clinical application, especially in the market of skin care products and cosmetics.

    As a skin care herb praised by ancient medical classics, 11 ethnic minorities in China, such as Bai, Dai, De'ang, Jingpo, Lisu, Miao, Mongolian, Mulao, Tu, Wa, and Yi still retain the traditional habit of using Bletilla for skin care in their daily life (Table 3). In addition to B. striata, B. formosana and B. ochracea are also used as substitutes. Although Chinese ethnic groups have different names for Bletilla spp., the skin care methods are basically the same. Dry Bletilla tubers are ground into a powder and applied to the skin[34], and this usage is also confirmed by the records in ancient medical texts[23, 24]. The various local names of Bletilla by different ethnic groups also indirectly suggests which ethnic groups play an important role in the traditional use. For example, Bai people called B. striata baijier (白鸡儿), goubaiyou (狗白尤), and yangjiaoqi (羊角七) (Table 3).

    Table 3.  The traditional medicinal knowledge of Bletilla in ethnic communities, China.
    Ethnic groupLatin nameLocal nameUsed partUse methodMedicinal effect
    AchangBletilla striata (Thunb. ex Murray) Rchb. F.BaijiTuberAfter the roots are dried, chew them orally or grind them into powder for external applicationTuberculosis, hemoptysis, bleeding from gastric ulcer, burns and scalds
    BaiBaijier, Goubaiyou, YangjiaoqiTuberTreatment of tuberculosis hemoptysis, bronchiectasis hemoptysis, gastric ulcer hemoptysis, hematochezia, skin cracking
    DaiYahejieTuberUsed for tuberculosis, tracheitis, traumatic injury, and detumescence
    De'angBageraoTuberTuberculosis, hemoptysis, bleeding from gastric ulcer, burns and scalds
    DongShaque, SanjueTuberTreat hematemesis and hemoptysis
    JingpoLahoiban, PusehzuotuberFor tuberculosis, bronchiectasis, hemoptysis, gastric ulcer, hematemesis, hematuria, hematochezia, traumatic bleeding, burns, impotence
    MengMoheeryichagan, NixingTuberFor tuberculosis hemoptysis, ulcer bleeding, traumatic bleeding, chapped hands, and feet
    MiaoBigou, Wujiu, SigouTuberUsed for hemoptysis of tuberculosis, bleeding of ulcer disease, traumatic bleeding, chapped hands, and feet
    MolaoDajiebaTuberTreat internal and external injuries caused by falls
    TibetanSanchabaijiTuberFresh chopped and soaked with honey; Powdered after sun-dried, then taken with honey and waterMainly used to treat cough, asthma, bronchitis, lung disease and a few gynecological diseases
    TuRuokeyeTuberAfter the roots are dried, chew them orally or grind them into powder for external applicationTreatment of tuberculosis, hemoptysis, bloody stool, chapped skin
    WaBaijiTuberAfter the roots are dried, chew them orally or grind them into powder for external applicationFor tuberculosis, hemoptysis, gastrointestinal bleeding, scald and burn
    YaoBiegeidaiTuberTreat gastric ulcer, pulmonary tuberculosis, cough, hemoptysis, and hematemesis
    YiDaibaij, Tanimobbaili, Niesunuoqi, AtuluoboTuberTreatment of tuberculosis, hemoptysis, golden wound bleeding, burns, chapped hands and feet
    ZhuangManggounuTuberTreat stomachache and hemoptysis
    BaiBletilla formosana (Hayata) Schltr.Baijier, YangjiaoqiTuberAfter the roots are dried, chew them orally or grind them into powder for external applicationIt is used for emesis, hemoptysis due to tuberculosis, and hemoptysis due to gastric ulcer. External application for treatment of incised wound
    MiaoLianwuTuberThe effect is the same as that of B. striata
    LisuHaibiqiuTuberIt can treat tuberculosis, hemoptysis, epistaxis, golden sore bleeding, carbuncle and swelling poison, scald by soup fire, chapped hands and feet
    YiNiesunuoqi, Yeruomaoranruo, Atuluobo, Ribumama, Atuxixi, Abaheiji, Binyue, ZiyouTuberIt is used for tuberculosis, hemoptysis, traumatic injury, treatment of frostbite, burn, scald, bed-wetting of children and other diseases
    BaiBletilla ochracea Schltr.Baijier, YangjiaoqiTuberAfter the roots are dried, chew them orally or grind them into powder for external applicationFor hematemesis, epistaxis, hemoptysis due to tuberculosis, hemoptysis due to gastric ulcer; External application of golden sore and carbuncle
    MengMoheeryichagan, NixingtuberThe effect is the same as that of B. striata
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    The formation of traditional medical knowledge among Chinese people is often directly related to the specific living environment and cultural background[34]. For example, the Bai, Dai, De'ang, Jingpo, Lisu Yi, Wa and other ethnic minorities live in mountainous areas. The cold weather in winter and year-round outdoor manual work makes it difficult to maintain their skin[35, 36]. In the face of this situation, the ethnic people who are concerned about their physical appearance have long ago chosen local Bletilla species for skin care, and have handed down this tradition for many generations[34]. This important traditional skin care tradition is worthy of further in-depth study.

    The six main classes of Bletilla chemical components, phenanthrene derivatives, phenolic acids, bibenzyls, flavonoids, triterpenoids, and steroids, have been described previously. Almost three hundred compounds have been isolated from Bletilla, including 116 phenanthrene derivatives, 58 phenolic acids, 70 bibenzyls, 8 flavonoids, 24 triterpenoids and steroid and 13 other compounds (Figs 514). Chemical structures of the isolates of Bletilla species most are phenanthrene derivatives, which have been demonstrated to possess various pharmacological activities.

    The prominent opioids oxycodone, hydrocodone, naloxone, and naltrexone are all phenanthrene derivatives[37]. Currently, phenanthrene derivatives (Fig. 5, 1 to 66) were isolated from B. formosana, B. ochracea, and B. striata. In 2022, 17 phenanthrene derivatives (117) were isolated from the ethyl acetate (EtOAc) extracts of B. striata tubers[38]. Then, other phenanthrene derivatives were isolated from Bletilla, such as dihydrophenanthrenes (1841), phenanthrenes (4266), biphenanthrenes (Fig. 6, 6789), dihydro/phenanthrenes with uniquestructures (90112) and phenanthraquinones (Fig. 7, 113116). Thus far, this genus has been documented to include these compounds, which have been shown to exhibit pharmacological actions[3945].

    Figure 5.  Phenanthrene derivatives from Bletilla species (1−66)[3841,4345,47,49,58,7072,7479].
    Figure 6.  Phenanthrene derivatives from Bletilla species (67−105)[41,43,49,5961,70,76,7986].
    Figure 7.  Phenanthrene derivatives from Bletilla species (106−116)[43,49,70,75,84,85,87].

    Phenolic acids are carboxylic acids created from the skeletons of either benzoic or cinnamic acids[4648]. Fifty-eight phenolic acids (Figs 810, 117 to 174) were isolated from B. formosana, B. ochracea, and B. striata.

    Figure 8.  Phenolic acids from Bletilla species (117−134)[1,5,36,4752,54,67,88,90].
    Figure 9.  Phenolic acids from Bletilla species (135−169)[39,45,4854,56,61,68,69,73,76,82,83,8994].
    Figure 10.  Phenolic acids from Bletilla species (170−174)[20,95].

    For example, compounds 121, 126, 139, 141, 148, 149, 154, 155 and 157 were isolated from the rhizomes of B. formosana[1,49,5052]. The structures of these compounds were determined, mostly from their NMR spectroscopy data. Additionally, protocatechuic (136) and vanillin (137) also have been isolated from B. striata[53]. Moreover, some bioactive components such as 2-hydroxysuccinic acid (164) and palmitic acid (165) have been discovered and identified from B. striata[20,5456].

    The bibenzyls were small-molecular substances with a wide range of sources, which were steroidal ethane derivatives and resembling the structural moiety of bioactive iso-quinoline alkaloids[57].

    For example, depending on their structural characteristics, 70 bibenzyl compounds (Fig. 11, 175 to 244) can be grouped into three groups, simple bibenzyls (175186, 233238), complex bibenzyls (189225) and chiral bibenzyls (226-232, 239-244)[5860].

    Figure 11.  Bibenzyls from Bletilla species (175-244)[1,4042,47,49,50,5860,70,73,76,9699].

    Flavonoids are among the most common plant pigments. Eight bibenzyls (Fig. 12, 245 to 252) have been isolated from B. formosana, B. ochracea, and B. striata. Apigenin (245) and 8-C-p-hydoxybenzylkaempferol (249) were isolated from the whole plant of B. formosana[45]. Bletillanol A (250), bletillanol B (251) and tupichinol A (252) were isolated from B. striata[61]. The names and chemical structures of the flavonoids reported from Bletilla are shown below (Fig. 12).

    Figure 12.  Flavonoids from Bletilla species (245–252)[45,61].

    Twenty-four triterpenoids and steroids (Fig. 13, 253 to 276) have been reported from Bletilla (Fig. 13), such as, tetracyclic triterpenes (253259) and pentacyclic triterpenes (189225) and chiral bibenzyls (260)[6264]. Steroids (261276) isolated from the Bletilla and have shown some bioactivity. For example, bletilnoside A (272) was isolated from Bletilla species and displayed anti-tumor activity[65,66].

    Figure 13.  Triterpenoids and steroid compounds from Bletilla species (253-276)[56,6265].

    Thirteen other compounds (Fig. 14, 277 to 289) were isolated from B. formosana, B. ochracea, and B. striata. These compounds included amino acids, indoles and anthraquinones[67,68]. For example, syringaresinol (285) and pinoresinol (286) have been described in the methanol extract of the tubers of B. striata[61].

    Figure 14.  Others compounds from Bletilla species (277−289)[50,54,61,62,67,68,94,97].

    Based on the information about the chemical constituents of Bletilla species, it appears that there is a substantial body of research on these compounds. However, there are some areas that may warrant further investigation and research. At first, it would be valuable to investigate potential synergistic effects and interactions between the different classes of compounds within Bletilla species, as some of the compounds may work together. Besides, it is worth considering the improvement of compound yield. Optimizing extraction methods and finding the most efficient and environmentally friendly techniques are vital for both research purposes and potential commercial applications. It is also important to take into account the variability in chemical composition among different Bletilla species and even within the same species from different cultivars.

    The rich and varied chemical components make the plants of Bletilla have a wide variety of pharmacological activities (Table 4). Many studies have shown that the plants of this genus have anti-inflammatory, antineoplastic, antiviral, antioxidant, hemostatic, antibacterial, and other biological activities, which help to support the traditional medicinal practice of Bletilla in folk medicine.

    Table 4.  Summary of the pharmacological activities of Bletilla species.
    Pharmacological activityTested substance/partTested system/organ/cellTested dose/dosing methodResultsRefs.
    Anti-inflammatoryEthanol extract of Bletilla striataRAW264.7 cells RAW264.7 cells were pre-treated with ethanol extract of B. striata for 1 h and then stimulated with LPS (200 ng/mL) for 12 h, 0.05% DMSO was applied as the parallel solvent control. The culture supernatant was collected for IL-6 and TNF-α detection.Ethanol extract of B striata significantly inhibited LPS-induced interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) expression at 2.5 µg/mL.[41]
    The ethyl acetate-soluble (EtOAc) extract of tubers of B. striataH2O2-induced PC12 cell injury modelPC12 cells were seeded in 96-well multiplates at a density of 1.5 × 105 cells/mL. After overnight incubation at 37 °C with 5% CO2, 10 μM test samples and H2O2 (final concentration of 450 μM) were added into the wells and incubated for another 12 h.It protected the cells with the cell viabilities of 57.86 ± 2.08%, 64.82 ± 2.84%, and
    64.11 ± 2.52%.
    [98]
    Ethanol extract of tubers of B. striataRAW264.7 cellsCells were treated with ethanol extracts (25 μM) dissolved in DMSO, in the presence of
    1 μg/mL lipopolysacchride
    (LPS) for 18 h
    The anti-inflammatory activity with IC50 of 2.86 ± 0.17 μM.[54]
    PE extract of the tubers of B. striataLPS-stimulated BV2 cellsCells treated with extract
    (0, 1, 10, 30, 100 μg/mL) and dihydropinosylvi (0, 1, 10, 30, 100 μM) in presence of LPS
    (1 μg/mL)
    The anti-inflammatory activity with IC50 values of 96.0 μM.[96]
    Ethanol extract of the roots of B. striataCox-1 and Cox-2Treated with the ethanol extracts at various concentrations
    (0, 1, 10, 100 μM)
    The compounds with sugar moieties displayed selective inhibition of Cox-2 (N90%).[38]
    B. striata polysaccharide (BSPb)Human mesangial cells (HMCs)HMCs were pre-treated with BSPb (5, 10, 20 μg/mL)BSPb efficiently mediated expression of NOX4 and TLR2, to attenuate generation of ROS and inflammatory cytokines.[12]
    Compounds extracted from the rhizomes of Bletilla ochraceaRAW264.7 cellsAfter 24 h preincubation,
    cells were treated with serial dilutions in the presence of
    1 μg/mL LPS for 18 h. Each compound was dissolved in DMSO and further diluted in medium to produce different concentrations. NO production in the supernatant was assessed by adding 100 μL of Griess regents.
    It showed the inhibitory effects with IC50 values in the range of 15.29–24.02 μM.[76]
    Compounds extracted from the rhizomes of B. ochraceaMurine monocytic RAW264.7 cellsAfter 24 h preinubation, RAW 264.7 cells were treated with compounds (25 μM) dissolved in DMSO, in the prenence of
    1 μg/mL LPS for 18 h. NO production in each well was assessed by adding 100 μL of Giress regent
    It showed the inhibitory effects with IC50 2.86 ± 0.17 μM.[86]
    Compounds extracted from the rhizomes of Bletilla formosanaElastase Release AssaysNeutrophils (6 × 105 cells/mL) were equilibrated in MeO-Suc-Ala-Ala-Pro-Val-p-nitroanilide (100 μM) at 37 °C for 2 min and then incubated with a test compound or an equal volume of vehicle (0.1% DMSO, negative control) for 5 min.Most of the isolated compounds were evaluated for their anti-inflammatory activities. The results showed that IC50 values for the inhibition of superoxide anion generation and elastase release ranged from 0.2 to 6.5 μM and 0.3 to 5.7 μM, respectively.[49]
    Anti-tumorTwo compounds from Bletilla striataA549 cellsCompounds were tested for their ability to induce ROS generation in A549 cells at concentrations of 20 two compounds for 24 h, the cells were harvested to evaluate the ROS production.The two compounds exhibited antiproliferative effects using the MTT test; these effects may be due to cell cycle arrest and inducing ROS generation.[87]
    Stilbenoids from B. striataBCRP-transduced K562 (K562/BCRP) cellsIt showed antimitotic activity and inhibited the polymerization of tubulin at IC50 10 μM.[78]
    Compounds extracted from the rhizomes of B. ochraceaThe human tumor cell lines HL-60 (acute leukemia), SMMC-7721 (hepatic cancer), A-549 (lung cancer), MCF-7 (breast cancer), and SW480 (colon cancer)100 μL of adherent cells were seeded into each well of 96-well cell culture plates. After 12 h of incubation at 37 °C, the test compound was added. After incubated for 48 h, cells were subjected to the MTS assay.All isolated metabolites except 7 were evaluated for cytotoxic activity against five human cancer cell lines (HL-60, SMMC7721, A-549, MCF-7 and SW480).[76]
    AntiviralThe tuber of B. striataMadin-Darby canine kidney model and embryonated eggs modelAs simultaneous treatment with 50% inhibition concentration (IC50) ranging from 14.6 ± 2.4 to 43.3 ± 5.3 μM.Phenanthrenes from B. striata had strong anti-influenza viral activity in both embryonated eggs and MDCK models.[107]
    The 95% ethanol
    Extract of B. striata
    BALB/C miceIt has significant anti-influenza
    virus effect in mice, which may be related to the increase of IL-2, INFα, INF-β and thus enhance the immune function of mice.
    [12]
    AntioxidantCompounds extracted from the rhizomes of B. formosanaDPPH radical-scavenging assaySolutions containing 160 μL of various concentrations of sample extract, 160 μL of various concentrations of BHA, 160 μL of various concentrations of ascorbic acid, and the control (160 μL of 75% methanol) were mixed separately with 40 μL of 0.8 mM DPPH dissolved in 75% methanol. Each mixture was shaken vigorously and left to stand for 30 min at room temperature in the dark.Tthe seedlings grown by tissue culture of B. formosan collected in Yilan County had the best antioxidant capacity. In addition, B. formosana collected in Taitung County had the best scavenging capacity in the tubers, leaves and roots.[93]
    Fibrous roots of B. striataDPPH model and superoxide anion systemThe ABTS+ solution was prepared by reacting 7 Mm ABTS with 2.45 mM potassium persulfate (final concentrations both dissolved in phosphate buffer, 0.2 M, pH 7.4) at room temperature for 12–16 h in the dark.It removed free radicals and inhibit tyrosinase activity.[33]
    B. striata extracts (BM60)The murine macrophage cells NR8383, male SD mice (180~200 g)NR8383 were pretreated with extracts (1, 10 and 100 g/mL) for 4 h and then 65 stimulated with 1 g/mL of LPS for 24 h. Acute lung injury was induced in mice by nonhexposure intratracheal instillation of LPS (3.0 mg/kg). Administration of the BM60 extract of 35, 70, and 140 mg/kg (L, M, H) was performed by oral gavages.The BM60 treatment reduced the production of NO in NR8383 macrophages. Treatments with BM60 at the doses of 35, 70, 140 mg/kg significantly reduced macrophages and
    neutrophils in the bronchoalveolar lavage fluid (BALF).
    [12]
    The crude
    polysaccharides obtained from B. striata
    DPPH free radical scavenging activityConcentration
    range of 2.5–5.0 mg/mL
    The IC50 of BSPs-H was 6.532 mg/mL.[35]
    HemostasisB. striata polysaccharide (BSP)Diabetes mellitus (DM) mouse models were induced by high fat-diet feeding combined with low-dose streptozocin injectionDM mouse models were induced by high fat-diet feeding combined with low-dose streptozocin injection. The BSP solutions were applied on the surface of each wound at a volume of 50 μl. RD mice were assigned as normal controls and received saline treatment (n = 6). All mice were treated with vehicle or BSP once daily from the day of wounding (d0) until 12 days later (d12).BSP administration accelerated diabetic wound healing, suppressed macrophage infiltration, promoted angiogenesis, suppressed NLRP3 inflammasome activation, decreased IL-1β secretion, and improved insulin sensitivity in wound tissues in DM mice.[112]
    B. striata Micron Particles (BSMPs)Tail amputation model and healthy male Sprague-Dawley (SD) rats
    (250 ± 20 g, 7 weeks of
    age)
    Rats were divided into six groups of five treated with cotton gauze and BSMPs (350–250, 250–180, 180–125, 125–75, and < 75 μm), respectively.Compared to other BSMPs of different size ranges, BSMPs of 350–250 μm are most efficient in hemostasis. As powder sizes decrease, the degree of aggregation between particles and hemostatic BSMP effects declines.[109]
    Rhizoma Bletillae polysaccharide (RBp)Adult male SD rats weighing 220 ± 20 gAfter incubation for 1 min at 37 °C, 300 μL of PRP was dealt with different concentrations of RBp (50, 100, 150, and 200 mg/L) under continuous stirring, and the vehicle was used as the blank control.RBp significantly enhanced the platelet aggregations at concentrations of 50−200 mg/L in a concentration-dependent manner.[113]
    AntibacterialBibenzyl derivatives from the tubers of Bletilla striataS. aureus ATCC 43300, Bacillus subtilis ATCC 6051, S. aureus ATCC 6538 and Escherichia coli ATCC 11775Using a microbroth dilution method, bacteria were seeded at
    1 × 106 cells per well (200 μL) in a
    96-well plate containing Mueller-Hinton broth with different concentrations (from 1 to 420 μg/mL, 300 μg/mL and so on;
    2-fold increments) of each test compound.
    It showed inhibitory activities with MIC of (3–28 μg/mL) against S. aureus ATCC6538[116]
    The crude extract of B. striataS. album, A. capillaris, C. cassiaThey were seeded at 1 × 106 cells per well (200 μL) in a 96-well plate containing Mueller−Hinton broth (meat extracts 0.2%, acid digest of casein 1.75%, starch 0.15%) with different concentrations (from 1 to 128 μg/mL; 2-fold increments) of each test compound.It showed S. album (0.10%), A. capillaris (0.10%), and C. cassia (0.10%) to have the strongest antibacterial properties.[118]
    The ethyl acetate-soluble (EtOAc) extract of tubers of B. striataS. aureus ATCC 43300, S. aureus ATCC 6538, and Bacillus subtilis ATCC 6051) and Escherichia coli ATCC 11775)Bacteria were seeded at 1 × 106 cells per well (200 μL) in a 96-well plate containing Mueller Hinton broth with different concentrations (from 1 to 420 μg/ml; 2-fold increments) of each test compound.The extract was effective against three Gram-positive bacteria with minimum inhibitory concentrations (MICs) of 52–105 μg/ml.[98]
    The phenanthrene fraction (EF60) from the ethanol extract of fibrous roots of Bletilla striata pseudobulbsS. aureus ATCC 25923, S. aureus ATCC 29213, S. aureus ATCC 43300, E. coli ATCC 35218, and P. aeruginosa ATCC 27853, Bacillus subtilis 168EF60 was active against all tested strains of Staphylococcus aureus, including clinical isolates and methicillin-resistant S. aureus (MRSA). The minimum inhibitory concentration (MIC) values of EF60 against these pathogens ranged from 8 to 64 μg/mL.EF60 could completely kill S. aureus ATCC 29213 at 2× the MIC within 3 h but could kill less than two logarithmic units of ATCC 43300, even at 4× the MIC within 24 h. The postantibiotic effects (PAE) of EF60 (4× MIC) against strains 29213 and 43300 were 2.0 and 0.38 h, respectively.[117]
    Anti-adhesiveBletilla striata extraction solutionPPA was induced by cecal wall abrasion, and Bletilla striata was injected to observe its efect on adhesion in ratsThe rats in the sham operation group was not treated; the other rats of the three experimental groups were intraperitoneally injected with 8 ml of phosphate-buffered saline (Control group), 15% Bletilla striata extraction solution (BS group), and 0.2% hyaluronic acid solution (HA group), respectively.Bletilla striata decreased the development of abdominal adhesion in abrasion-induced model of rats and reduced the expression of the important substance which increased in PPAs.[120]
    ImmunomodulatoryB. striata polysaccharide (BSPF2)Mouse spleen cellsTo observe the immune activity of BSPF2, mouse spleen cells were stimulated with BSPF2 at 10–100 g/mL for 72 h.Immunological assay results demonstrated that BSPF2 significantly induced the spleen cell proliferation in a dose-dependent manner.[121]
    Anti-pulmonary fibrosisB. striata polysaccharideClean grade male SD ratsSD rats were randomly divided into 5 groups, sham operation group (equal volume of normal saline), model group (equal volume of normal saline), tetrandrine positive control (24 mg/kg) group and white and Polysaccharide low
    (100 mg/kg) and high (400 mg/kg) dose groups.
    The Bletilla striata polysaccharide has remarkable regulation effect on anti-oxidation system and immune system, but cannot effectively prevent lung fibrosis.[127]
    Small molecule components of Bletilla striataClean grade male SD ratsSD rats were randomly divided into 5 groups, sham operation group (0.5 mL normal saline), model group (0.5 mL normal saline), and positive control group (tetrandrine 24 mg/kg) and low (20 mg/kg) and high (40 mg/kg) dosage groups of the small molecule pharmacological components of Bletilla, which were administered by gavage once a day for 2 consecutive months.The small molecule components of Bletilla striata can effectively prevent lung fibrosis though regulating the anti-oxidation system,immune system and cytokine level; SMCBS is one of the active components of Bletilla striata on silicosis therapy[124]
    —, not given.
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    Many phytochemicals have been well characterized to lessen swelling or inflammation[89]. A series of phenolic acid and polysaccharide compounds isolated from Bletilla demonstrated anti-inflammatory bioactivity against BV-2 microglial, RAW 264.7, and PC12 cells[96,100102]. For example, phochinenin K (106) exhibited growth inhibitory effects with an IC50 of 1.9 μM, and it is a possible candidate for development as neuroinflammation inhibitory agent[43]. Using the H2O2-induced PC12 cell injury model, (7S)-bletstrin E (242), (7R)-bletstrin F (243) and (7S)-bletstrin F (244) could clearly protect the cells with the cell viabilities of 57.86% ± 2.08%, 64.82% ± 2.84%, and 64.11% ± 2.52%, respectively[98]. With an IC50 of 2.86 ± 0.17 μM, 2,7-dihydroxy-4-methoxyphenanthrene (53) showed potential action against NO generation in RAW 264.7 macrophages[54]. The use of Bletilla in traditional skin care, it is said to function as an astringent, hemostatic and wound healing[33]. Modern medical pharmacology research has validated that this plant has antibacterial effects, which may may help to explain, in part, its traditional use in skin care[24].

    Though it's mentioned that some of these compounds from Bletilla have demonstrated anti-inflammatory action, more extensive studies are needed to fully understand their mechanisms of action, potential therapeutic applications, and safety profiles. Conducting in vivo studies and clinical trials can provide more concrete evidence of their effectiveness.

    There are important antineoplastic agents that have originated from plant natural products[103]. In recent years, several bibenzyl and flavonoid compounds have been discovered from Bletilla that have antineoplastic activity against A549 cells and other cells. For example, 7-hydroxy-2-methoxy-phenanthrene-3,4-dione (160) and 3′,7′,7-trihydroxy-2,2′,4′-trimethoxy-[1,8′-biphenanthrene]-3,4-dione (163) have shown strong antiproliferative effects and induced ROS production after 24 h in A549 cells[87]. The doxorubicin (Dox)/FA (folate)-BSP-SA (stearic acid) modified Bletilla striata polysaccharide micelles boosted the drug enrichment in tumors and improved the in vivo anticancer effects[104,105]. Micelles, nanoparticles, microspheres, and microneedles are examples of B. striata polysaccharide-based drug delivery systems that exhibit both drug delivery and anti-cancer functionality. These experiments confirmed that some of the compounds isolated from the Bletilla have potential activity for the treatment of cancer.

    However, most of the evidence presented in the previous studies is based on in vitro experiments or cell culture studies. It is highly necessary to use animal models to study the in vivo anti-tumor effects of Bletilla extracts or compounds. These studies can help evaluate the safety and effectiveness of treatments based on Bletilla. Additionally, through such methods, researchers can further investigate the mechanisms of Bletilla's anti-tumor activities, exploring how Bletilla compounds interact with cancer cells, immune responses, and signaling pathways involved in tumor growth and metastasis.

    Antiviral medications are essential for preventing the spread of illness, and are especially important nowadays with pandemics and drug-resistant viral strains[5, 6]. Therefore, it is vitally necessary to find novel, safe, and effective antiviral medications to treat or prevent viral infections[106]. B. striata plant contains compounds that have been recorded in ancient texts to cure cough, pneumonia, and skin rashes, and these may be related to potential antiviral constituents[23]. Some constituents of B. striata have antiviral activity, for example, phenanthrenes and diphenanthrenes from B. striata displayed potent anti-influenza viral in a Madin-Darby canine kidney model and embryonated eggs model, diphenanthrenes with parentally higher inhibitory activity than monophenanthrenes[107]. But more research is needed to further determine the antiviral activity of Bletilla, understand how Bletilla compounds interact with viral proteins or the host immune response, and conduct safety and toxicity studies, which are crucial for the development of related materials.

    Free radicals have the potential to exacerbate lipid peroxidation and harm cell membranes, which can lead to several prevalent human diseases, including cancer, cataracts, and coronary heart disease[108]. Research has shown that extracts from Bletilla possess strong antioxidant activity. However, this antioxidant activity can vary depending on the different growing environments of the plant. Additionally, the antioxidant capabilities of extracts from different parts of the Bletilla plant also vary[93]. Clinical studies have shown that traditional Chinese medicine formulas containing Bletilla can inhibit tyrosinase activity and possess antioxidant properties, thus resulting in skin-whitening effects[108]. Furthermore, some research reveals that the polysaccharides in the plant exhibit significant antioxidant activity, effectively scavenging free radicals and inhibiting tyrosinase activity[33]. This highlights the skin-whitening potential of the fibrous root of Bletilla striata, indicating promising prospects for the comprehensive utilization of the B. striata plant[33]. However, most studies on the pharmacological activities of Bletilla have focused solely on B. striata, neglecting other species within the genus. Different species may possess varying phytochemical compositions and antioxidant properties, which can lead to an incomplete understanding of the genus as a whole.

    Available hemostatic agents are expensive or raise safety concerns, and B. striata may serve as an inexpensive, natural, and promising alternative[109]. Polysaccharides of B. striata displayed hemostatic activity through inhibition of the NLRP3 inflammasome[110112]. The ADP receptor signaling pathways of P2Y1, P2Y12, and PKC receptors may be activated as part of the hemostasis[113]. Alkaloids from Bletilla have hemostatic activities through platelet deformation, aggregation, and secretion. In addition, polysaccharides of Bletilla striata have potential wound-healing medicinal value[110]. Currently, Bletilla plants have been used in various traditional systems, such as traditional Chinese medicine and Ayurveda, to control bleeding.

    Previous studies revealed that Bletilla displayed antibacterial effects[114]. For example, bletistrin F, showed inhibitory activities with MIC of (3–28 μg/mL) against S. aureus ATCC 6538[115,116]. Antimicrobial screening of Bletilla showed S. album (0.10%), A. capillaris (0.10%), and C. cassia (0.10%) to have the strongest antibacterial properties[117,118]. In addition, phenanthrenes are worthy of further investigation as a potential phytotherapeutic agent for treating infections caused by S. aureus and MRSA[119]. However, further in vivo studies on the antibacterial activity of Bletilla are lacking, which is needed for clinical application. For example, the specific mechanism of antibacterial activity of Bletilla still needs to be elucidated. While research on the antibacterial activity of Bletilla plants is promising, it faces several shortcomings and challenges that need to be addressed for a more comprehensive understanding of their potential therapeutic applications. Further studies with standardized methodologies, mechanistic insights, clinical trials, and consideration of ecological and safety concerns are essential to advance this field.

    There are other pharmacological activities of Bletilla, like anti-fibrosis activity, anti-adhesive activity, and immunomodulatory activity. For example, B. striata has been studied as a new and cheaper antiadhesive substance which decreased the development of abdominal adhesion abrasion-induced model in rats[120]. However, the natural resources of Bletilla are also getting scarcer. To preserve the sustainable development of Bletilla species, proper farming practices are required, along with the protection and economical use of these resources. The immunomodulatory activity of the Bletilla species was assessed using the 3H-thymidine incorporation method test, and BSP-2 increased the pinocytic capacity and NO generation, which improved the immunomodulatory function[121,122].

    B. striata extract was shown to have anti-pulmonary fibrosis effect[123]. B. striata polysaccharide can successfully prevent lung fibrosis through established by invasive intratracheal instillation method and evaluated by lung indexes[123,124]. Moreover, Bletilla species need further investigations to evaluate their long-term in vivo and in vitro activity before proceeding to the development of pharmaceutical formulation.

    While there is currently a deep understanding of the pharmacological activity of plants in the Bletilla genus, there are still many gaps that need to be addressed. To overcome these shortcomings, future research on the pharmacological activity of Bletilla species should emphasize comprehensive, well-designed studies with a focus on species-specific effects, mechanistic insights, and rigorous clinical trials. Additionally, collaboration among researchers, standardization of methods, and transparent reporting of results can help advance our understanding of the therapeutic potential of Bletilla plants. Researchers should also consider safety aspects and explore potential herb-drug interactions to ensure the responsible use of Bletilla-based therapies.

    There are several common clinical applications of Bletilla striata in TCM. The gum of B. striata has unique viscosity characteristics and can be used as thickener, lubricant, emulsifier and moisturizer in the petroleum, food, medicine, and cosmetics industries[125130]. B. striata is used as a coupling agent, plasma substitute, preparation adjuvant, food preservative and daily chemical raw material[131133]. In clinical practice, B. striata glue has also been proven to control the infections and is beneficial to the healing of burns and wounds[133135].

    In ethnic communities in Southwest China, the locals chew fresh Bletilla tubers directly or take them orally after soaking in honey to treat cough, pneumonia and other diseases[33, 34]. This traditional use is common in local communities in Southwest China, and suggests at the safety of Bletilla. However, current research shows it is still necessary to control the dosage when using Bletilla[136].

    Zebrafish embryos and larvae respond to most drugs in a manner similar to humans[137]. Militarine, the main active ingredient of Bletilla, was tested in a zebrafish embryo development assay at concentrations of 0.025 g/L and 0.05 g/L, and with the increased concentration, the heart rate of zebrafish embryos is slowed. Mortality and malformation rates of zebrafish embryos gradually increased with time and militarine concentration[138]. Although Bletilla species are safe at therapeutic dose ranges, further research on their safety is required[136]. More in-depth studies should be carried out on Bletilla to extract effective ingredients and make better preparations for clinical use[139].

    According to the traditional medicinal knowledge in ancient Chinese texts, Bletilla has been an important ingredient for skin care since ancient times. Many ethnic minority groups in China still retain the practice of using Bletilla for skin care, and the plant parts and preparation methods of use are consistent with the records in ancient texts. Almost 300 phytochemicals have been identified from Bletilla, and some of them possess important pharmacological activities, which support its traditional uses and suggest the important medicinal development potential of this genus. This review has demonstrated that Bletilla, as an important medicinal plant of Orchidaceae, still requires further research to fathom its medicinal potential.

    For instance, it is necessary to enhance the quality control procedures based on the chemical components and pharmacological activity of Bletilla. The chemical composition and pharmacological properties of Bletilla are critical areas of current research. According to previous studies, the main bioactive components of Bletilla can vary greatly according to its origin, harvest time, distribution, storage, and adulteration. However, variation in bioactivities caused by the differences in Bletilla constituentshave not been explored extensively yet. To develop clinical applications of Bletilla, it is crucial to further explore the mechanism of action between its chemical composition variation and its pharmacological actions.

    In addition, although the tuber has historically been the main medicinal part of Bletilla, research has shown that the chemical composition in other parts of Bletilla, such as stems, leaves, and flowers, also give these parts a variety of pharmacological activities. Further in-depth analysis of the chemical components and pharmacological activities of different parts of this genus is worthwhile, to explore the specific chemical basis of its pharmacological activities, develop related drugs, and promote clinical applications. For example, Bletilla polysaccharide has good hemostasis and astringent wound effects[110], so it may have the potential to be developed into a drug or related medical materials to stop bleeding and heal wounds.

    Finally, as a cautionary note, many unrestrained collections and the destruction of habitats have made the resources of wild Bletilla rarer. In addition to protecting the wild populations of Bletilla, appropriate breeding techniques should be adopted to meet the commercial needs of this economically important genus, thereby allowing its sustainable use in commerce.

    The authors confirm contribution to the paper as follows: study conception and design, funding acquirement: Long C; data analysis, draft manuscript preparation, literature review: Fan Y, Zhao J; manuscript revise and language editing: Wang M, Kennelly EJ, Long C. All authors reviewed the results and approved the final version of the manuscript.

    The raw data supporting the conclusion of this article will be made available by the authors, without undue reservation, to any qualified researcher. Requests to access these datasets should be directed to Yanxiao Fan (fanyanxiao0510@163.com).

    This research was funded by the Yunnan Provincial Science and Technology Talent and Platform Plan (202305AF150121), Assessment of Edible & Medicinal Plant Diversity and Associated Traditional Knowledge in Gaoligong Mountains (GBP-2022-01), the National Natural Science Foundation of China (32370407, 31761143001 & 31870316), China Scholarship Council (202206390021), and the Minzu University of China (2020MDJC03, 2022ZDPY10 & 2023GJAQ09).

  • The authors declare that they have no conflict of interest.

  • Supplemental Table S1 Basic data from mushroom cultivation experiment on four different straws.
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  • Cite this article

    Grimm D, Sonntag E, Rahmann G. 2024. Oyster mushroom cultivation on cereal and legume straw of poor feed quality. Studies in Fungi 9: e010 doi: 10.48130/sif-0024-0010
    Grimm D, Sonntag E, Rahmann G. 2024. Oyster mushroom cultivation on cereal and legume straw of poor feed quality. Studies in Fungi 9: e010 doi: 10.48130/sif-0024-0010

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Oyster mushroom cultivation on cereal and legume straw of poor feed quality

Studies in Fungi  9 Article number: e010  (2024)  |  Cite this article

Abstract: This study explores the viability of cultivating oyster mushrooms on cereal and legume straw of poor feed quality, investigating oyster mushroom productivity, and the implications for mass-, nitrogen- and carbon flows within the agricultural system. Four types of straw (wheat, maize, faba bean, and soy bean) were utilized as substrates for mushroom cultivation. Fresh yields varied widely, from 114% biological efficiency on maize straw to 58% on wheat straw, while dry yields ranged from 9.2% biomass conversion rate on maize straw to 3.8% on wheat straw. The protein content of mushrooms varied between 16.8% on wheat straw and 23.2% on faba bean straw, correlating with the nitrogen content of the straw. Furthermore, results revealed significant variations in carbon emissions, ranging from an estimated 3.5 kg (on wheat straw) to 2.6 kg (on soy straw) emitted per kg of dry mushroom produced. These findings underscore the importance of substrate selection in mushroom cultivation, with implications for agricultural resource management and food production. Depending on the focus, different substrates may be considered as optimal. While maize straw produced most mushrooms in this study, soy bean straw emitted the least carbon in relation to yield, faba bean straw produced mushrooms with higher protein content, and wheat straw retained the most nitrogen in the spent mushroom substrate.

    • Oyster mushrooms are the second most cultivated mushroom species in the world, with about 19% of market share[1]. The grey oyster mushroom (Pleurotus ostreatus) is among the most versatile and robust mushroom species, as it can be cultivated on an extensive range of agricultural residues without the need for complete substrate sterilization[2,3]. Even though it is possible to grow oyster mushrooms on wood or straw, many mushroom farmers use substrate ingredients, which could alternatively be used as feed, like cotton seed hulls or bran, which is a commonly recommended substrate supplement[4,5]. While supplementation with nitrogen-rich, edible ingredients can increase mushroom yields[2], the use of substrates which cannot be used as food or feed is more sustainable in the context of food security and agroecology[6]. Also, little is known about the influence of different substrates on carbon emissions during the mushroom cultivation process. Since mushrooms, like animals, are heterotroph organisms, it is important to investigate how their cultivation could contribute to climate change. Another aspect of sustainability in mushroom production is the crop rotation system from which the substrates are sourced, since sustainable crop rotation can reduce the need for fertilizers. Legumes are an important part of crop rotation due to their ability to increase soil nitrogen, and can increase the productivity of cereal crops that are cultivated on the same plot afterwards[7,8]. Cereal crops are rich in carbohydrates and provide a lot of calories, while legumes are rich in proteins and fats, so a combination of the two can provide most of the macronutrients needed for human nourishment[9]. Oyster mushrooms are rich in vitamins and minerals[10] and are a good meat substitute due to their amino acid profile and high protein content[1113], which makes them a valuable addition to a diet mostly based on cereals and legumes. Mushroom production does not compete with other food production on farmland, as it is nearly 'landless'[6]. However, it can compete with animal husbandry if feed-grade substrates are used. We stipulate that the ideal straw for oyster mushroom cultivation is so nutrient-poor that it provides too little metabolic energy (ME) and digestible protein for feeding a 60 kg goat. A 60 kg goat needs 9.7 MJ of metabolizable energy (ME) and 70 g of digestible protein for its maintenance needs, which it has to draw from a maximum of 1.4 kg feed (dry matter = DM) which it can eat per day[14]. Therefore, 6.93 MJ of ME and 50 g of digestible protein must be available per kg of feed DM. With this baseline, it is guaranteed that the substrate has very little value as feed and for most other agricultural use cases apart from organic matter in the soil. The crops providing the straws for our study were chosen partly due to their high relevance as staple crops and partly to represent typical legumes and cereal crops from temperate climate zones (faba bean and wheat) and from more tropical regions (soy bean and maize). With the experiment we conducted, using these straws to cultivate oyster mushrooms, we want to answer the following research questions:

      (1) What is the nutrient composition and feed quality of the different straws?

      (2) What is the oyster mushroom production potential of the different straws?

      (3) How much carbon and nitrogen are retained in the spent mushroom substrate (SMS) and what are the implications for the need of fertilizer or compost use on the field?

      (4) How much carbon is emitted in the process of mushroom cultivation?

    • Straw from two cereal crops and two legumes was used in the experiment: maize (Zea mays, variety Saludo), wheat (Triticum aestivum, variety Faustus), soy bean (Glycine max, a mix of varieties Merlin, GL Melanie, Marquise, Aurelina, ES Favor, RGT Sphinxa, ES Comandor, Amarok, and Arcadia) and faba bean (Vicia faba, variety Tiffany). All straws were produced with certified organic farming practices[15], which ensures that there are no remains of fungicides on the material, which could influence mushroom growth. Maize, faba bean, and wheat were cultivated in 2019 under scientifically controlled conditions at the experimental station of the Thünen-Institute of Organic Farming in northern Germany. To get a nutrient-poor maize straw despite using a feed variety of this crop (sweet maize varieties cannot be cultivated in cold, northern German climate), the maize was left standing in the field for four months after harvest season before cutting it, allowing nutrients to leach back into the soil. Soy was grown at the organic experimental station Gladbacher Hof of the University Giessen in central Germany. The different straws included all the above-ground parts of the plant, except the grain, and the cobs in the case of maize. All the straws were chopped (< 2 cm) and dried for 5 d at 40 °C for storage.

      Grain spawns with the mycelium of P. ostreatus ((Jacq.: Fr.) P. Kumm, strain number: P10001, type of grain: wheat) was used to inoculate the straws for mushroom cultivation.

    • The experiment consisted of four treatments (wheat, maize, soy, and faba) with eight replicates. Each replicate consisted of a polypropylene mushroom grow bag with a micropore filter (50 cm × 8 cm × 0.1 cm, Hemoton brand®) filled with 800 g of moist, pasteurized substrate (200 g dry matter and 600 g water) and 20 g of mushroom grain spawn (6.6 g dry matter). Hot air pasteurization at 100 °C for 3 h was used to pasteurize the substrate. Grain spawn was added to the substrate after letting it cool down, ensuring that the spawn was well distributed by twisting and shaking the bags. The mushrooms were cultivated under controlled conditions in the laboratories of the Thünen-Institute, at 21 °C and 90% humidity in a grow-box (HOMEbox Vista Medium), as depicted in Fig. 1.

      Figure 1. 

      Different substrates are used for mushroom cultivation in a random replication approach in a grow chamber.

      Since it was intended to use the same amount of dry matter and water in the different treatments, but the straws had different water-holding capacities, the replicates were hung in a way that allowed excess water to drip from a small opening at the bottom.

    • Up to three flushes were harvested from each replicate. The fresh weight of the harvested mushrooms was determined immediately after harvest. The dry yield was determined after drying at 105 °C for 24 h. From this data, the biological efficiency (BE, percentage of dry matter of substrate converted to fresh matter of mushrooms[2] and the biomass conversion rate (BCR, percentage of dry matter of substrate converted to dry matter of mushroom) were calculated. The visually discernible occurrence of bacteria or molds in each replicate was checked and the mycelial growth (from 0% of substrate colonized to 100%) was estimated weekly during the first three weeks of the experiment. After the cultivation period, the substrate was removed from the bags, crushed, and dried at 105 °C for 24 h, to determine the dry weight of each replicate and to take samples for chemical analyses. All raw data on mushroom yield and the composition of SMS is made available in the Supplemental Table S1 to be published with this study.

    • The nitrogen (N) and carbon (C) content of the spawn, straw, SMS and mushrooms were analyzed with the DUMAS-method[16]. The protein content (XP) of the straw and mushroom was estimated by multiplying the nitrogen content with the factor 6.25, which is commonly used in the analyses of feed[17]. Carbon emissions through respiration of the fungal mycelium are estimated by subtracting the amount of carbon found in the SMS and the mushrooms from the amount present in the straw before cultivation. The crude fiber (XF) of the straw was determined with the Weender-van Soest analysis[18]. The number of analyses were focused on SMS. While only one collective sample from the straw, spawn and mushrooms were taken, a separate sample from the SMS of each replicate was analyzed. To assess whether the type of straw influences the protein composition of the harvested mushrooms, three more samples from mushrooms cultivated on the same straw under the same conditions were analyzed a year later and are included in the results of this study. All analyses were carried out in the laboratory of the Thünen-Institute of Organic Farming.

    • To calculate the metabolizable energy (ME) of the different straws for ruminants, the following formula was used[19]:

      ME (MJ) = 0.0312 * digestible fat (g) + 0.0136 * digestible fiber (g) + 0.0147 * (digestible organic matter (g) – digestible fat (g) – digestible fiber (g)) + 0.00234 * raw protein (g)

      The data on the digestibility of the different fractions of the maize and wheat straw were taken from the publications of the German association for agriculture[19], while the data on faba bean straw was taken from the Dutch central feedstuff databank[20]. For soy bean straw, only incomplete data could be found. Information for the digestibility of organic matter and of protein of soy straw was found on the Feedipedia database[21]. To fill in the missing values on the digestibility of lipids and fibers in soy straw, we used the data on straw from a similar legume, namely the pea, Pisum sativum, from the DLG[19]. The compiled digestibility data can be found in Table 1.

      Table 1.  Digestibility of the different macronutrient fraction in the different straw types: Digestible organic matter (DOM), digestible protein (DP), digestible lipids (DL) and digestible fiber (DF).

      Straw type DOM (%) DP (%) DL (%) DF (%)
      Wheat 47 20 49 53
      Faba bean 52 46 53 42
      Maize 72 50 64 68
      Soy bean 52 54 55 42
    • For statistical analysis, Microsoft Excel and the freeware R-studio (version 4.0.3) were used. One-way analysis of variance (ANOVA) and the posthoc Tukey's test were used to compare different treatments and show significant differences. To test for the assumptions of normal distribution of the data and the residuals, histograms, and qq-plots were assessed and the Shapiro-Wilk test was used.

    • The chemical analysis (Table 2) showed large differences between the types of straw with regard to the nitrogen content, while the carbon content was almost the same. The wheat straw contained the least nitrogen and faba bean contained the most. The carbon/nitrogen-ratio (C/N-ratio) of the straws varied from 45 to 130. The content of crude fiber content (XF) was lowest in maize straw followed by soy bean, wheat, and faba bean. The mushroom spawn had a notably higher nitrogen content than the straws with a C/N-ratio of 15.6.

      Table 2.  Chemical composition of the dry matter (DM) of different straws and mushroom spawn used for oyster mushroom cultivation.

      Sample C (% DM) N (% DM) C/N-ratio XF (% DM)
      Wheat straw 47.12 0.36 130.37 47.97
      Faba bean straw 47.12 1.05 44.75 49.86
      Maize straw 47.07 0.68 69.72 38.03
      Soy bean straw 47.18 0.59 79.91 43.86
      Mushroom spawn 46.33 2.96 15.63 x

      In combination with the data in Table 1, the digestible protein and metabolizable energy were calculated. As Table 3 shows, wheat straw had the least digestible protein, while faba bean had the most. Maize straw, according to these calculations, had the most metabolizable energy.

      Table 3.  Protein, digestible protein (DP) and metabolic energy (ME) of the different straws for 1 kg dry matter and 1.4 kg dry matter (estimated daily feed intake of a goat).

      Sample Protein DP ME
      g/kg
      DM
      g/kg
      DM
      g/1.4 kg
      DM
      MJ/kg
      DM
      MJ/1.4 kg
      DM
      Wheat straw 19.4 3.9 5.4 6.3 8.8
      Faba bean straw 63.0 29 40.5 7 9.8
      Maize straw 38.9 19.5 27.2 9.8 13.7
      Soy bean straw 33.7 18.2 27.4 7.2 10.1
    • In the 56 days of the experiments, most replicates produced two mushroom harvests, with a few replicates producing only one or even three harvests. No clear pattern was discernible between treatments in terms of number of harvests. The occurrence of green mold was limited to one replicate of the wheat straw treatment and two replicates of the maize straw treatment. Since these replicates failed to produce mushrooms, they were taken out of the experiment, reducing the number of replicates in wheat straw to seven and in maize straw to six. Mycelial growth was the fastest in the soy bean straw treatment, where all replicates were fully colonized after 13 d, while the replicates in other treatments were fully colonized after 21 d.

      Wheat straw produced significantly lower yields than all other treatments, both in terms of fresh matter (BE) and dry matter (BCR). Maize straw produced significantly more mushrooms than all other treatments in terms of fresh yield but not significantly more than soy straw in terms of dry yield (Table 4).

      Table 4.  Fresh and dry yield.

      Treatment Fresh matter BE (%) Dry matter BCR (%)
      Wheat straw 58b (12.5) 3.8c (0.8)
      Faba bean straw 76bc (17.3) 6.6b (1.4)
      Maize straw 114a (10.2) 9.2a (0.9)
      Soy bean straw 89.1b (14.7) 8.6a (1.3)
      Biological efficiency (BE) and biomass conversion rate (BCR) of the different treatments. Significant differences between treatments are marked by letters above the data. Standard deviation given in brackets behind the mean.

      While wheat, faba bean, and soy bean straw produced more than 75% of the total dry yield in the first harvest, maize straw on average produced more than 50% of the mushrooms in the second and third harvests (Fig. 2).

      Figure 2. 

      Average dry yield per dry substrate distributed over different harvest flushes in the different treatments. Error bars show standard deviation.

      The composition of mushrooms from the different treatments is presented in Table 5. Mushrooms cultivated on faba bean straw contained significantly more nitrogen and thus protein than mushrooms from the other treatment.

      Table 5.  Chemical composition of the mushrooms from different treatments.

      Treatment C (%) N (%) C/N Protein (%)
      Wheat straw 44.7a (1.1) 2.7b (0.3) 16.8b 16.8 (1.6)
      Faba bean straw 45.4a (1.2) 3.7a (0.2) 12.2a 23.2 (1.3)
      Maize straw 45.1a (0.8) 3b (0.2) 14.9b 19 (1.4)
      Soy bean straw 45.6a (0.6) 2.8b (0.2) 16.2b 17.7 (1.6)
      Standard deviation given in brackets behind the mean. Significant differences between treatments are marked by letters above the data.

      By synthesizing the yield data and the chemical analysis, one can estimate the amount of protein produced per kg of straw. On wheat straw, 6.4 g protein were produced per kg of straw, on soy bean straw 15.2 g, on faba bean straw 15.4 g and on maize straw 17.4 g.

    • The change in nitrogen and carbon content of the straws after cultivation differed notably between the different treatments. While the C/N ratios of wheat, maize, and soy bean straw were decreased by mushroom cultivation, it slightly increased on faba bean straw (Table 6).

      Table 6.  Chemical composition of the spent mushroom substrate (SMS).

      SMS type C (% DM) N (% DM) C/N C/N ratio change
      Wheat straw 45.5 (0.9) 0.4 (0) 106.0 −24.4
      Faba bean straw 45.6 (0.4) 1 (0) 47.3 2.6
      Maize straw 43.8 (0.4) 0.7 (0) 62.7 −7.0
      Soy bean straw 43.9 (0.4) 0.6 (0) 71.7 −8.3
      Standard deviation of carbon and nitrogen content given in brackets after the mean. C/N change is the difference in the C/N ratio in comparison to the ratio of the straw before mushroom cultivation.

      The amount of dry matter, carbon, and nitrogen from the straw that remained in the SMS after cultivation is presented in Table 7. Dry matter, carbon and nitrogen reduction was notably lower in wheat straw than in the other treatments. The strongest reduction in all these metrics occurred in the treatment with maize straw. In terms of emissions per unit of mushrooms, wheat straw emitted the most carbon, with 3.5 kg per 1 kg of dry mushrooms, while soy straw emitted the least, with 2.6 kg.

      Table 7.  Mass transfer from straw to spent mushroom substrate in the different treatments.

      Treatment Dry matter (%) C (%) N (%)
      Wheat straw 82.2 (6.4) 79.5 (5.6) 79.3 (12.3)
      Faba bean straw 70.1 (5) 67.9 (4.6) 60.5 (3.9)
      Maize straw 63.4 (1.9) 59 (1.7) 59 (3.9)
      Soy bean straw 67.1 (1.9) 62.4 (1.6) 61.5 (4)
      Standard deviation given in brackets behind the mean.

      By subtracting the amount of dry matter in the SMS (Table 7) and in the mushrooms (Table 5) from the amount of dry matter in each replicate at the beginning of the experiment (200 g straw + 6.6 g spawn), the unaccounted rest was calculated. This rest is the amount of carbon that was lost to respiration by the mushroom. As can be seen in Fig. 3, in the wheat treatment, 17% of the dry matter are estimated to be carbon emissions, 25% in the faba bean treatment, 32% in the maize treatment and 29% in the soy treatment.

      Figure 3. 

      Dry matter transfer from the straw to different fraction (spent mushroom substrate, mushrooms and carbon emissions) during mushroom cultivation.

    • None of the straws used for mushroom cultivation in this study can be considered as good feed for goats or other ruminants, since none would provide both enough energy and protein for metabolic basic needs. Therefore, the use for mushroom production as supplementary food for humans is a sustainable choice, as long as the SMS is brought back to the soil for organic matter.

    • The best-performing straws in the experiment were maize and soy straw, which were almost evenly matched in terms of dry yield. There were however interesting differences between these two treatments, which could be relevant to mushroom producers. On one hand, maize straw produced more fresh yield than soy straw, which may be related to differences in crude fiber contents and the physical structure of the two materials. While soy straw is coarse and hard, maize straw is very soft and sponge-like and could thus better provide the mycelium with water and air, as for example, Stamets discusses[2]. Interestingly, soy produced more mushrooms than maize in the first flush, indicating that the nutrients were more accessible to the mushroom. Unlike the other substrates maize straw produced more than half of its total dry yield in the second and third harvests. From an economic and space-use efficiency standpoint, it could thus be beneficial for mushroom producers to harvest only once from all straws except maize. Maize yields were high in comparison to other studies[2224]. Soy bean straw produced comparable results to another study, which used different species of oyster mushrooms[25]. No studies were found utilizing faba bean straw. The results in this study concerning yield from wheat straw, were in the range of other studies, with some having higher yields[26] and some lower[27]. The low nitrogen content of the wheat straw used in this study surely contributed to the low productivity.

      If we take the view of Stamets that an oyster mushroom cultivator should operate at around 100% BE or more, to be economical[2], the faba bean and wheat straw can be said to be un-economical if used as pure substrates. However, the validity of this view may differ in different markets and depending on the profit made through the use of SMS. Looking at the nutrient composition of the different straws, it is notable that faba bean straw produced relatively few mushrooms despite its high nitrogen content. This is supported by the fact that the C/N ratio increased in faba bean straw as a result of mushroom cultivation, indicating that there was more nitrogen available than necessary for the mushroom. The significantly increased protein content of mushrooms produced on faba bean straw in comparison to the other treatments is also most likely a result of this effect. This substrate may be more efficiently utilized in oyster mushrooms production, if mixed with a more carbon rich material.

    • The removal of dry biomass from the different straws during the cultivation process, displayed in Fig. 3, was in the range of other studies[26]. However, the distributions that were found are roughly equivalent to that presented by Stamets[2], who writes that around 10% of the biomass of a substrate is turned into mushrooms and 70% into SMS.

      Significant amounts of nitrogen were removed from the straw by the mushrooms in all treatments, with the lowest removal found in wheat straw and the highest in maize straw. While the value of the SMS as fertilizer is higher than that of straw due to the decreased C/N ratio, this nevertheless means that more nitrogen would be removed from the field than if the straw was used as mulch. Therefore, the removal of straw from fields for mushroom cultivation might make it necessary for farmers to return nitrogen through application of fertilizers. It would also be possible to mix SMS with other materials like dung and compost them, to solve this problem.

      Carbon removal from the straw by the respiration of oyster mushroom mycelium was also significant and roughly in the same range as nitrogen. Large differences were found between the treatments in terms of the carbon that was emitted during mushroom cultivation. Wheat straw emitted the least carbon. However, in terms of emissions per unit of mushrooms, wheat straw emitted the most carbon, while soy straw emitted least. In terms of greenhouse gas emissions, mushroom production on legume straw was more sustainable than on cereal straw. However, to get a complete picture, a full live cycle assessment has to be conducted and the emissions caused by pasteurizing the substrate and during the cultivation phase also have to be accounted for. Nevertheless, the carbon emissions associated with mushroom cultivation will most likely be quite low compared to other protein sources such as goat meat or other animal products[28]. Further research into this topic should be conducted.

    • Using nutrient-poor straw from cereals and legumes for oyster mushroom cultivation is an efficient and sustainable way of producing protein-rich food in very little space. Even substrates that have almost no value as feed can be used in this way, which can increase the economic return of cropland, if unused straw will be used for mushroom production. Maize stover was found to be the best straw, followed by soy straw, which also produced high yields. While wheat straw produced inferior yield, faba bean straw had mediocre yields, but produced mushrooms with a higher protein content. Since significant amounts of carbon and nitrogen are removed from the straw through mushroom production, it is necessary to increase fertilizer or compost application to the field where straw was removed, even if the SMS is returned as an organic amendment.

    • The authors confirm contribution to the paper as follows: study conception and design: Grimm D, Sonntag E, Rahmann G; data collection: Grimm D; analysis and interpretation of results: Grimm D, Rahmann G; draft manuscript preparation: Grimm D. All authors reviewed the results and approved the final version of the manuscript.

    • The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

      • The authors declare that they have no conflict of interest.

      • Copyright: © 2024 by the author(s). Published by Maximum Academic Press, Fayetteville, GA. This article is an open access article distributed under Creative Commons Attribution License (CC BY 4.0), visit https://creativecommons.org/licenses/by/4.0/.
    Figure (3)  Table (7) References (28)
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    Cite this article
    Grimm D, Sonntag E, Rahmann G. 2024. Oyster mushroom cultivation on cereal and legume straw of poor feed quality. Studies in Fungi 9: e010 doi: 10.48130/sif-0024-0010
    Grimm D, Sonntag E, Rahmann G. 2024. Oyster mushroom cultivation on cereal and legume straw of poor feed quality. Studies in Fungi 9: e010 doi: 10.48130/sif-0024-0010

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