Analysis Of Structural Diversity Characteristics Of Microbial Flora In The Fermentation Of Clear Sauce-flavor Liquor In Different Seasons

Microbial diversity in Baijiu fermentation process has been a hot topic.It lays a solid foundation for understanding the microbial community structure and function of traditional brew liquor fermentation.However,most of the studies did not account for the season of sample collection in the experimental design,ignoring the possible differences of fermentation microorganisms in different brewing seasons.The Fen-Maotai-flavored liquor is still in the initial stage of development.The research on the diversity of its brewery microorganisms is relatively few,especially in the different seasons.The diversity of microbial community structure of the Fen-Maotai-flavored liquor fermentation is not clear,which to a certain extent restricts the improvement of liquor quality and its production regulation.Therefore,the microbial community structure diversity of the Fen-Maotai-flavored liquor is still in the initial stage of development liquor in four seasons of spring,summer,autumn and winter was analyzed and compared by using high throughput sequencing technology.Meanwhile,the metabolism of volatile flavor compounds in fermented grains during different seasons was analyzed by headspace solid phase microextraction combined with gas chromatography-mass spectrometer(HS-SPME-GC-MS).The main conclusions were as follows:(1)In the fermented grains of spring,summer,autumn and winter,24 bacteria and 6 fungi were detected.Among them,Firmicutes and Proteobacteria are the main bacteria in the fermentation process,Ascomycota and Zygomycota are the main bacteria in the fermentation process.(2)499 genera and 251 genera of fungi were detected from fermented grains in spring,summer,autumn and winter.The dominant bacteria(relative abundance of at least 1% in one sample)are Lactobacillus,Gluconobacter,Bacillus,Pedioccus,Brevundimonas,Oxyphotobacteria?unclassified ? Acetobacter ? Pseudomonas ?Mitochondria?Unclassified,ZOR006,Weissella,Virgibacillus,Staphylococcus,Eschericia,Klebsiella,Enterobacter,Kozakia,Scopulibacillus and Kroppenstedtia.With the progress of fermentation,the bacterial community structure of fermented grains in four seasons was dominated by Lactobacillus,with an average relative abundance of 84.21 %-99.69 %.The dominant fungi(relative abundance of at least1% in one sample)are Saccharomyces,Rhizopus,Saccharomycopsis,Hyphopichia,Cyberlindera,Thermomyces,Paeciomics,Thermomyces,Thermoascus,Wickerhamomics,Preussia,Meyerozyma,Talamomics,Zygosaccharomomics,Sordarimomycetes?unclassified ? Plectosphaerella ? Nectria ? Aspergillus ?Auriculariales?Incertae?sedis?Unclassified,Cladosporium and Torulaspora.(3)Through analysis and comparison,the dominant microorganisms in the fermentation process of Fen-flavored,Maotai-flavored and Fen-Maotai-flavored Baijiu(at least one sample relative abundance >1%)were found to be the dominant bacteria of Gluconobacter,Brevundimonas,ZOR006,Virgibacillus,Escherichia,Klebsiella,Scopulibacillus and Kozakia in the fermentation process of Fen-Maotai-flavored liquor.Saccharomyces,Rhizopus,Hyphopichia,Cyberlindnera,Paecilomyces,Preussia,Talaromyces,Plectosphaerella,Nectria,Cladosporium and Torulaspora are the dominant fungi in the fermentation of Fen-Maotai-flavored Baijiu.(4)Volatile flavor compounds were detected in fermented grains of Fen-Maotai-flavored Baijiu in different seasons.58 volatile flavor compounds were detected,including 7 kinds of alcohols,5 kinds of acids,29 kinds of esters,9 aromatic compounds and 8 other kinds of substances.The first stage(0-5 days)is the main period of alcohol production,aromatic compounds and acid production in four seasons,while the middle and late fermentation(10-25 days)is the main period of ester production in four seasons.(5)There are some differences in the content and change of volatile flavor substances in fermented grains in different seasons.The content of acid and ester in fermented grains increased with the increase of fermentation time in four seasons.Ethyl acetate and ethyl lactate were higher in all the esters in the fermented grains in the four seasons.At the end of fermentation,the content of ethyl acetate and ethyl lactate in the fermented grains in autumn were 346.27±6.09 mg/kg,respectively In addition,the 2-octanol,2-butanol,lauryl alcohol,2-butanediol,2-butanediol in the fermented grains in autumn were higher than those of the other three seasons,(6)There are some differences in the variation of the main bacteria in the fermentation process of fermented grains in different seasons,which is caused by the interaction of internal control factors(microbial interaction)and external regulatory factors(external environmental factors).The correlation analysis of the main microbial succession and the change of volatile flavor substances in fermentation showed that there was a strong positive correlation between Bacillus and2,3,5,6-tetramethylpiperazine,2,3,5-trimethylpiperazine and acetonitrile(P ? 0.71);Lactobacillius has a positive correlation with most volatile flavor substances;The positive correlation between Saccharomyces and 2-octanol,2-butanol,lauryl alcohol,n-propanol,2,3-butanediol,furfuranol and isopentanol was strong(P ? 0.79).