Succession Characteristics Of Microbiotaand Characteristic Microbes In Vinegar Brewing During Summer And Winter

In recent years,vinegar makers in China had suffered from controlling difficultly of the brewing process during high temperature seasons and the abnormal phenomena such as turbidity,stickiness and flatulence also appeared in the finished vinegar,thereby seriously affecting the nutritional composition and quality of vinegar.The quality of vinegar is closely related to the microbial metabolism in the fermentation process.In order to further understand the steady-state brewing mechanism of vinegar in high-temperature condition,the microbial community in vinegar brewing process during summer and winter and characteristic spoilage microbes in spoilage vinegar were comprehensively and thoroughly investigated using molecular ecology technology.This study had obtained the following research results:1.The structure of bacterial community in vinegar brewing process during summer and winter was investigated by Illumina high-throughput sequencing and the results showed that the structure of bacterial community in summer and winter had significant statistical differences?p<0.05?.In summer,as a whole the richness of bacterial community in acetic acid fermentation period was greater than that in alcohol fermentation period,while the richness of bacterial community in alcohol fermentation period was greater than that in acetic acid fermentation period in winter,and the composition of bacterial community in each stage of acetic acid fermentation period had high similarity in both seasons.The richness?except the 6th day of alcohol fermentation?and diversity the?except the 3rd and 6th day of alcohol fermentation?of bacterial community in winter was higher than that in summer.The bacterial community in summer came from 8 phyla and 51 genera,in which 12 genera?relative abundance>0.1%?were first detected during the fermentation of Shanxi mature vinegar.In winter,the bacterial community belonged to 22 phyla and 226 genera,in which6 genera?relative abundance>0.1%?were first detected.The dominant bacterial phylum and genus were Firmicutes and Lactobacillus,respectively,in both seasons.The effects of seasonality on the low-abundance genera were much higher than that on the dominant genera.2.The structure of fungal community in vinegar brewing process during summer and winter was investigated by Illumina high-throughput sequencing.In summer,the richness of fungal community in acetic acid fermentation period were higher than that in alcohol fermentation,and the similarity of fungal flora composition among different fermentation stages was low.In winter,the richness of fungal community in acetic acid fermentation period were less than that in alcohol fermentation period,and the composition of fungal community in acetic acid fermentation period showed a higher similarity than that in alcohol fermentation period.In winter the richness and diversity of fungal community during alcohol fermentation were greater than those in summer,while in winter the richness and diversity of fungal community during acetic acid fermentation were lower than those in summer.In summer,the fungal community belonged to3 phyla and 35 genera,in which 7 genera?relative abundance>0.1%?were first detected.In winter,the fungal community came from 4 phyla and 46 genera,in which 15 genera?relative abundance>0.1%?were first detected.The dominant bacterial phylum and genus were Ascomycota and Saccharomyces,respectively,in both seasons.In winter the diversity of molds and yeasts with relative abundance over 0.1%were much higher than that in summer.3.4 stable bacterial consortium and 46 bacterial strains were isolated from5 different batches of spoilage vinegar samples and 44 strains of them belonged to the genera Rummeliibacillus,Enterococcus,Vagococcus,Lactobacillus,Bacillus,Staphylococcus,Brevundimonas,Paenibacillus,respectively,while the other two isolated strains came from unknown genera.The strong gas-producing bacterial consortium TYF-LIM-L09 was mainly composed of six bacterial genera,in which the dominant one was Lactobacillus?45.77%?.The gas produced by TYF-LIM-L09 was CO₂ and the highest volume percentage concentration could reach 71.43%.The gas production decreased with the decrease of pH value and the increase of ethanol concentration.TYF-LIM-L09,with high ethanol?8%v/v?and salt?13%w/v?tolerance,could tolerate the pH value decreased to 5.5 and grow rapidly at 50?,with an optimum temperature of 45?.Rummeliibacillus sp.TYF-05,with high ethanol?7.5%v/v?and salt?13%w/v?tolerance,could tolerate the pH value decreased to 5.5 and grow rapidly at55?,with an optimum temperature of 45?.Rummeliibacillus sp.TYK-07,with high ethanol?7.5%v/v?and salt?13%w/v?tolerance,could tolerate the pH value decreased to 5.0 and grow rapidly at 55?,with an optimum temperature of 45?.4.When glucose and natural corn stover were used as a sole carbon source,respectively,the highest metabolites of TYF-LIM-L09,TYF-05 and TYK-07were ethanol and acetone,ethanol and ethanol,ethyl acetate and acetoin respectively.The strain TYK-07 could produce important aroma substances of vinegar.The main product contents of TYF-LIM-L09,TYF-05 and TYK-07 on6 different carbon sources showed that the ethanol yield of TYF-LIM-L09 was the highest when starch was used as the sole carbon source,with a concentration of 9.3 mM;strain TYF-05 had the highest ethanol yield on natural corn straw,with a concentration of 5.6 mM;strain TYK-07 also had the highest acetoin yield when natural corn straw was used as the sole carbon source,with the concentration of 150.8 mM.