Figures (3)  Tables (1)

    • Figure 1. 

      Process diagram for the traditional production of Daqu.

    • Figure 2. 

      The production pathways of the main aroma substances in Daqu. Green represents the enzymes involved in each stage, while red indicates the aromatic compounds produced.

    • Figure 3. 

      The main pathways of saccharification metabolism in Daqu. Green represents hexoses, and blue represents pentoses.

    • Types of enzymes Microbial sources Refs
      Type Genera
      Enzymes related to carbohydrates metabolism,
      EC 3.2.1.X      		 Amylase Bacteria Bacillus; Kroppenstedtia; Leuconostoc; Staphylococcus; Thermoactinomyces [57,62,65,71,83]
      Fungi Aspergillus; Byssochlamys; Penicillium; Rhizomucor; Saccharomycopsis; Thermoascus [50,62,84]
      Glucoamylase Bacteria Leuconostoc; Weissella [85,86]
      Fungi Aspergillus; Byssochlamys; Monascus; Rhizomucor; Rhizopus [84,87−90]
      Pectinase Bacteria Enterococcus [85,86]
      Fungi Eurotium; Streptomyces [91,92]
      Glucosidase Fungi Aspergillus; Lichtheimia; Saccharomycopsis; Paecilomyces; Thermoascus [50,89,93−95]
      Xylanase Fungi Aspergillus [88]
      Cellulase Fungi Penicillium [50]
      Hemicellulase Fungi Thermomyce [62]
      Enzymes related to proteins metabolism,
      EC 3.4.X.X      		 Neutral protease Bacteria Bacillus; Lactobacillus; Staphylococcus [54,57,70,71,96,97]
      Fungi Aspergillus; Eurotium; Lichtheimia; Mucor; Penicillium; Rhizomucor; Rhizopus [44,50,62,87,93,
      94,97]
      Acid proteases Fungi Saccharomycopsis [52,98,99]
      Fibrinolytic enzyme Fungi Rhizopus [97]
      Fibrinogenase Bacteria Bacillus [70]
      Enzymes related to esters metabolism,
      EC 3.1.1.X      		 Lipase Bacteria Bacillus [54,71,100]
      Fungi Eurotium; Rhizomucor; Rhizopus [87,89,97]
      Esterase Bacteria Bacillus; Leuconostoc; Staphylococcus; Weissella [65,70,71,85,97]
      Fungi Issatchenkia; Lichtheimia; Mucor; Monascus; Penicillium; Streptomyces; Zygosaccharomyces [44,50,57,66,78,
      89,94,95,101]
      Other enzymes Tannase Bacteria Bacillus [65]
      Fungi Aspergillus; Penicillium [50,93]
      Alkaline phosphatase Fungi Streptomyces [57]
      Phosphate hydrolase Fungi Streptomyces [57]
      Glycosyltransferase Fungi Rhizopus [87,97]

      Table 1. 

      The sources of enzymes with different functions in Daqu.