Study On The Diversity Of Yeast Resources In Maotai Town's Maotai-flavor Baijiu

The unique brewing environment and brewing process of Maotai-flavor Baijiu created a special microflora,and finally formed the unique Baijiu style of Maotai-flavor Baijiu.Its unique open fermentation makes the brewing environment,brewing Daqu,microorganisms in the air migrate into the fermentation process.Yeast is the main driving force of alcohol fermentation and is widely found in the brewing environment.During the storage of Maotai-flavor Daqu,yeast was continuously enriched from the brewing environment and air to ensure the normal fermentation of Baijiu.Therefore,the analysis of the yeast relationship between brewing environment and Maotai-flavor Daqu,as well as the yeast metabolism of flavor substances,is of great significance to reveal the brewing mechanism,optimize the process control and improve product quality.In this study,high-throughput sequencing technology and traditional separation method were used to systematically analyze the yeast community structure and change rules in the brewing environment and high temperature Daqu 1-7 rounds,and the differences among the metabolites of the isolated yeast were analyzed by simulating solid-state fermentation.The main results are as follows:(1)A total of 53 yeast genera were detected from the brewing environment and high-temperature Daqu for brewing using high-throughput sequencing technology.Fifty-one species of yeast were detected in the brewing environment,and 39 species of yeast were detected in the high-temperature Daqu.The dominant yeast genera in the brewing environment are Saccharomycopsis,Wickerhamomyces,Cryptococcus,Debaryomyces,Brettanomyces,Rhodotorula and unclassified?Saccharomycetaceae.The dominant yeast genera of high temperature Daqu are Saccharomycopsis,Wickerhamomyces and Millerozyma.For the first time,14 new species of yeast were detected during the fermentation of Maotai-flavor Baijiu(Agaricostilbum?Arachnomyces?Bullera?Cystofilobasidium?Dioszegia?Erythrobasidium ?Fellomyces? Filobasidium ? Gibellulopsis ? Kuraishia ? Eremothecium ? Ballistisporomyces ?Aessosporon and Kurtzmanomyces).The diversity and abundance of yeast in the brewing environment were different from that in the high-temperature Daqu.(2)Eighteen genera and 36 species of yeast were isolated from the fermentation environment and high temperature Daqu by culturable methods.A total of 25 yeast species were identified in the brewing environment and 22 yeast species were identified in high temperature Daqu.W.anomalus?S.cerevisiae?C.glabrata and T.asahii are the core yeasts of the brewing environment.S.fibuligera and W.anomalus are the core yeast of high temperature Daqu.Seven unreported yeast species were isolated for the first time(Trichosporon faecale?Issatchenkia sp.S612Y5?Kazachstania solicola?Pseudozyma sp.?Zygosaccharomyces sp.H2Y3?Helicoceras oryzae and Nectaromyces rattus).There were differences in the diversity and abundance of culturable yeast in the 7 fermenting environments and in the high-temperature Daqu,the diversity and abundance of yeast in the brewing environment were significantly different,and the diversity and abundance of yeast in the high-temperature Daqu were slightly different.The high throughput sequencing results and culturable results showed that the yeast community structure was stable in Daqu at high temperature,and characteristic yeast could be used as one of the criteria to test the quality of Daqu.(3)The key volatile compound 186 from 34 yeast fermentation products was determined by SPME-GC-MS,These include ketones,alcohols,esters,fragrances,aldehydes,hydrocarbons,pyridine rings,acids,ethers,carbonyl groups,amines,furans and other compounds.The types and contents of metabolites varied widely among the 34 strains with different metabolic capacities.Among them,HQ19 metabolized pyridines,H33 metabolized esters,H35 metabolized alcohols,Q34 metabolized furans and aromatic compounds,and H5 metabolized ketones had advantages.The relative contents of amines,carbonyl groups and other compounds are very low.Cluster analysis of volatile components in metabolism of 34 strains of yeast showed that the metabolites of different yeast were different.Among them,the simultaneous metabolism of 19 compounds in Q22 has advantages.H17,Q20,HQ25,HQ26,H31 and Q35 can simultaneously metabolize more than 5 compounds with relatively high content,which can be further studied as key strains.