Research On Microbiota Dynamics In Traditional Solid-state Fermentation Process And Enzyme Production Of The Prominent Strains In Chinese Vinegar Daqu

Daqu is widely used in traditional vinegar and spirit, and plays an important driver in solid-state fermentation process of traditional Chinese vinegar. The quality of Daqu has an important effect on the flavor formation of the final products of vinegar or wine. In this study, the physical indicators and microbial diversity of Daqu, which was sampled from a vinegar factory in Shanxi province, was determined and analyzed. The results indicated that the moisture continued to decline and keep between 12% and 15% until the end of fermentation. The titratable acidity slightly increased from days 1 to 3 and the maximum value was approximate to 0.19 mmol/g on day 3, followed by a decline. Meanwhile, the pH value kept betweem 4.31 and 6.38. The contents of total starch were above 60% on process and the contents of reducing sugar with a fluctuation then declined to 21.0 mg/g dry Daqu. Amylase and glucoamylase activities clearly increased to maximum of 1,800 U and 1.01 U, respectively.The microbial CFU of surface layer was higher than middle layer, microbial CFU of center is the lowest. Bacterial CFU was higher than fungal CFU with a trend increased first and then declined. The similar trend was obtained by quantitative PCR, compared to microbial CFU by palte technique. The results of PCR-DGGE and 16S/18 SrRNA gene clone library revealed that the dominant bacteria included orders of Enterobacteriales, Actinomycetales, Bacillales and Lactobacillales, while the preminant fungi included orders of Eurotiales, Saccharomycetales and Mucorales.Using plating technique, nine isolates were picked with amylase activity. Four strains among them showed good amylase activity with the maximum activity 50.86 U/mL, 39.52 U/mL, 34.82 U/mL and 29.32 U/mL respectively, and were identified to Pediococcus pentosaceus, Bacillus licheniformis, Saccharomycopsis fibuligera and Pantoea sp. by 16S/18 S rRNA sequencing analysis, respectively. The other five strains showed low amylase activity, and all were under 5 U/mL. Theses results indicated that the Lactobacillales and Pantoea sp. were the major contributors of amylase and glucoamylase activities in early stages, while Bacillales play an important role at last stages of Daqu fermentation process.