Screening And Application Of Tetramethylpyrazine Functional Bacteria In Qingxiang Liquor Brewing

Qingxiang liquor is made of sorghum as the main raw material and low temperature daqu as the starter,and its production process is essentially the process of microbial fermentation.In this process,a series of flavor substances such as alcohols,aldehydes,esters,acids and pyrazines are produced,which enrich the flavor of liquor and are also the main source of functional components in liquor.Among them,tetramethylpyrazine(TTMP),an amide alkaloid,is an important functional component of liquor.It is soluble in organic solvents but insoluble in cold water,and has a series of effects such as vasodilation,improving microcirculation and inhibiting platelet aggregation.In order to improve the quality and health value of clear flavor liquor,this paper isolated and screened the strain with high yield of tetramethylpyrazine from the clear flavor liquor Daqu.After the process optimization,it was applied to the brewing process of liquor,which was of great significance to improve the quality and drinking value of liquor.(1)Screening and identification of tetramethylpyrazine-functional bacteria.Seven strains producing TTMP were isolated and purified from Daqu liquor and screened by gas chromatography.Among them,q94 and q33 produced the highest amount of TTMP0.36±0.01 g/L and 0.16±0.02 g/L,respectively,and were identified as Bacillus subtilis and Bacillus licheniformis by morphological and molecular biological analysis.(2)Optimization of fermentation medium composition and synthesis process of tetramethylpyrazine by functional bacteria.The results showed that when 80 g/L sucrose was used as carbon source,10 g/L peptone and 20 g/L yeast leaching powder were added,the yield of tetramethylpyrazine was higher,and the addition of inorganic potassium dihydrogen phosphate(15 g/L)significantly increased the yield of tetramethylpyrazine.The yield reached 3.32±0.18 g/L after optimizing the medium components.The inoculum amount,initial p H,fermentation time,heat treatment temperature and time were further optimized by single factor and response surface experiments.The results showed that inoculum amount was 6.00%,p H6.8,fermentation for 160 h and heat treatment for 1 h at85℃,at which the yield of TTMP could reach 5.65±0.21 g/L.Application of tetramethylpyrazine functional bacterial solution.The optimized functional bacteria solution was added into jiupei along with daqu at the mixing stage into the brewing system.Samples were taken at 0,5,10,20,and 30 days of brewing to measure the microbial changes in fermented grains.The results showed that the addition of functional bacteria solution significantly increased the content of tetramethylpyrazine in liquor by regulating the microbial structure 2.27±0.33 mg/L,which was nearly 30 times higher than that of the control,and had no significant effect on other main flavor substances in liquor.