The Microbial Diversity In Xifeng-Daqu

Daqu is a traditional fermentation starter that is used for Chinese liquor production,and it contributes not only to saccharification fermentation agent but also to flavoring agent.The microbial composition of Daqu determined the flavor of Chinese liquor.Xifeng is one of eight famous Chinese wines,but few study was focused on microbial populations from the Daqu.Therefore,culturable microorganism was characterized and identified using plate separation,morphological observation,PCR-RFLP and phylogenetic analysis.Moreover,16S rDNA PCR-DGGE was used to reveal microbial community and change of dominant populations.Finally,based on analysis of Daqu’s physiochemical properties,we tried to revealed microbial populations function and their influencing factors.The results were as follows:The number of culturable bacteria and mold in Xifeng-Daqu samples showed that the change is as firstly increased followed by decreased,then rise again,and down.Amount of bacteria in 15Q was the least,in 30Q was largest.For the molds,trend of number is firstly increased followed by decreased,and then down to stable.It was the least at initial stages and counted most on the first 10 days.From the trend of the overall number variation of microbial groups,we can obtain,the number of bacteria was 1 to 2 orders of magnitude higher than the number of molds,and temperature was an important factor in the quality of Daqu.The 193 bacterias were divided into 49 genotypes based on 16S rDNA PCR-RFLP.The sequence alignment and phylogenetic analysis suggested that the isolates were mainly involved in 42 species of 22 genus,of which Enterobacter,Bacillus,Brevibacterium,Staphylococcu,Acinetobacter,Zhihengliuella,Arthrobacter and Corynebacterium contributed the dominant bacteria species in the fermentation of Daqu.In addition,Enterobacter spp.were main group,accounting for nearly 28%.Furthermore,16 genotypes obtained from 163 molds based on 5.8S rDNA-ITS PCR-RFLP,they belonged to 14 species in 10 genus,of which Aspergillus,Rhizomucor,Penicillium,Galactomyces and Rhizopus were dominant.Aspergillus and Rhizomucor biggest group and accounted for 70%of the total number of mold.Meanwhile,PCR-DGGE method was applied to investigate structure of bacterial community in Duqu,the phylogenetic analysis showed bacteria belonged to Lactobacillus,Bacillus,Weissella,Terrabacter and Cellulosimicrobium.Lactobacillus spp.was broadly distribution in Daqu.When the physiochemical features were tested and analyzed,Xifeng-Daqu samples showed that moisture,acidity,liquefying power and saccharifying power could be affect by microbial diversity in Xifeng-Daqu.At the same time,the amounts and types of the Daqu microbes would also make changes in Daqu’s physiochemical indicators.