Analysis Of Lactic Acid Bacteria Metabolism For Lactic Acid Production In Acetic Acid Fermentation Stage Of Shanxi Aged Vinegar

Shanxi aged vinegar is a famous vinegar in China with unique taste and flavor,whichadopts solid state fermentation technology.Many kinds of microorganisms participate in the fermentation process.Among them,lactic acid bacteria are the main dominant bacteria group and the main producing bacteria of lactic acid.Has an important influence.However,the current understanding of the metabolic activity of lactic acid bacteria in the fermentation process of Shanxi aged vinegar remains unclear,which restricts the development of the vinegar industry.In this dissertation,the metabolic pathways of lactic acid during fermentation of vinegar were studied by molecular biology methods,and combined with the changes in fermentation conditions,the lactic acid anabolism characteristics of the dominant lactic acid bacteria were analyzed in depth and the lactic acid anabolism of lactic acid bacteria during the acetic acid fermentation of Shanxi aged vinegar was obtained.The law helps to further understand the brewing mechanism of vinegar and provides a theoretical basis for vinegar process optimization and process control.The microbiological succession and physicochemical index change of acetic acid fermentation stage in Shanxi aged vinegar were analyzed.The results showed that Lactobacillus was the main microorganism in the acetic acid fermentation process,and its relative abundance accounted for more than 50%of the microorganisms,combined with the changes of main physical and chemical indicators.CCA correspondence analysis was conducted and it was found that ethanol,acetic acid,temperature and reducing sugar were the main factors affecting the succession of lactic acid bacteria.In addition,Lactobacillus helveticus,Lactobacillus fermentative,Lactobacillus acidophilus and Lactobacillus plantarum were identified as acetic acid-related lactic acid bacteria and producing relatively high lactic acid.The growth and acid-producing ability of lactic acid bacteria during acetic acid fermentation were analyzed.The results showed that L.plantarum AFl-1,L.fermentum AF4-5 were the most abundant during the fermentation process and L.plantarum AF1-9,L.fermentum AF4-5 were the main acid-producing bacteria.Lactobacillus fermentum AF4-5,the acid-producing strain,had the highest viable count and transcription level,and L.plantarum AF1-9 had the highest average transcription level.Ethanol was the main factor affecting the average transcription level of L.plantarum AF1-9 in the early stage of fermentation,and acetic acid was the main factor affecting the average transcription level of L.fermentum AF4-5 in the middle and late fermentation.According to the fermentation conditions,the growth of lactic acid bacteria,acid production and acid production gene transcription levels were analyzed.The results showed that when the concentration of ethanol and acetic acid were higher than 3g/100g vinegar mash and 1.5g/100g vinegar mash respectively,the growth and acid production of lactic acid bacteria were significantly inhibited and the transcriptional level of the key genes at low concentration was higher than that at high concentration.When the fermentation temperature was 37? or 45 ?,the growth of lactic acid bacteria,acid production and the transcriptional level of the key genes is significantly higher than that of 30?.When the concentration of the fermentation substrate(glucose)was 2g/100g vinegar mash,the growth of lactic acid bacteria,the production of acid-producing and acid-producing genes were all significantly higher than that of lg/100g,3.5g/100g.These results indicated that changes in fermentation conditions would affect the production of lactic acid by lactic acid bacteria,and controlling the fermentation conditions in the production process can promote the fermentation to favor the production of lactic acid,thus improving the traditional fermentation methods and enhancing the quality of vinegar.