Study On Wenwanggong Baijiu Microbial Community Structure And Its Association With Main Flavoring

The solid-state fermentation of natural multi-strains is an important procedure for the Baijiu,a type of traditional Chinese distilled alcoholic beverage.The complex microbial diversity of the solid-state fermentation ecosystem and the synergistic effects of the enzymes and compounds produced by them are responsible for the special flavor and mouth feel of this beverage.During the spontaneous mixed-culture fermentation,enormous species diversity is a key feature,and significantly affects the quality of the pit mud and the zaopei.In this paper,the microbial community and volatile flavor compounds of the 2,20,30-years of pit mud and the corresponding zaopei during fermentation were analyzed.Microbial community dynamics were analyzed by high-throughput sequencing to identify the microbiota present during the fermentation.The volatile flavor compounds were analyzed by HS-SPME-GC-MS.In addition,correlation analysis between physicochemical parameters,predominant microorganism and important volatile flavor compounds was carried out to explore the potential role of microorganisms during the fermentation of the pit mud and the zaopei.The main research contents are as follows:(1)The results of physicochemical factors in the new pit mud showed lower p H and available phosphorus but higher calcium content;During the fermentation in zaopei,the moisture,acidity and alcohol showed an overall upward trend while the starch and reducing sugars showed a significant downward because of the decomposition and utilization of mildew and yeasts;For the pit mud,we identified 8 potent odorants with an ROAV value ?1 to be characteristic markers: ethyl hexanoate,ethyl octanoate,caproic acid,p-cresol,octanoic acid,ethyl butyrate,ethyl 3-phenylpropionate and valeric acid;We also determined 5 odorants to be potential characteristic markers of zaopei: caproic acid,ethyl hexanoate,ethyl octanoate,4-methylphenol and ethyl butyrate;Moreover,we also detected 5 and 11 amino acids in pit mud and zaopei samples,respectively.The total amino acids in 2-years pit mud were the highest.As the fermentation proceeds,the total amino acid in zaopei featured an increase and then a decrease.(2)The 16S rDNA high-throughput sequencing results showed that the bacterial microorganisms in the pit mud belonged to 6 phyla,25 genera,and the bacterial microorganisms in the zaopei belonged to 9 phyla,44 genera;Spearman correlation analysis results showed that the p H value,moisture content,and ammonium nitrogen content of pit mud were the most significant physicochemical factors affecting the bacterial microbial flora,and they are all negative related to Lactobacillus;The moisture,acidity and alcohol content in zaopei had a strong positive correlation with Lactobacillus;The ethyl hexanoate,Ala and Met were also positively correlated with Lactobacillus both in the pit mud and zaopei.(3)ITS high-throughput sequencing results showed fungi were only detected in wall and bottom pit mud of 2 years.The fungal microorganisms in the pit mud belonged to 4phyla,25 genera,and the fungal microorganisms in zaopei were classified into 3 phyla,28 genera;Spearman correlation analysis showed that the moisture content and p H were negative related to the unclassified Ascomycota in pit mud,but the content of ammonium nitrogen was negative related to the relative abundance of Pichiaceae and Saccharomycetaceae in pit mud;However,both the moisture,acidity and alcohol content in the zaopei had a significant positive correlation with the Pichiacea;We also found the ethyl hexanoate and free amino acids had a significant correlation with Pichiaceae,Saccharomycetaceae and unclassified Ascomycota both in the pit mud and zaopei.In summary,our results characterized the succession patterns and functional roles of the microbial diversity and flavor metabolites throughout the Baijiu fermentation process,especially in pit mud and zaopei.This study would contribute to a deeper understanding of the role of microbiota during the solid fermentation of Baijiu and be significant for improving the quality stability of Baijiu.