High-density Cultivation Of High-yield ?-aminobutyric Acid Strains In Sayram Yogurt Optimization Of Conditions And Preparation Of Starter

Sayram Town is located in Baicheng County,Aksu Region,Xinjiang.The town has a superior geographical location,providing high-quality pastures for animal husbandry and laying the foundation for high-quality milk sources.The previous research of the research group found that Sayram yogurt contains a higher content of functional factor ?-aminobutyric acid(GABA)than similar yogurt products,and the microorganisms of raw milk and yogurt in Sayram Town are diverse.Sex analysis and screening of high-yield?-aminobutyric acid strains confirmed that the high-yielding GABA strain was Lactobacillus delbrueckii subspecies.Bulgaria S33-32.In this paper,the S33-32 strain selected by the research group in the early stage is the research object,and further explores the factors affecting the increase of GABA production.Optimize the type of carbon source and the amount of carbon source,the type of nitrogen source and the amount of nitrogen source,the amount of sodium L-glutamate,and the fermentation conditions in the M17medium through response surface analysis,and on this basis,the GABA-producing strain S33-32high-density fermentation culture,followed by screening of GABA-producing starter vacuum freeze-drying protective agent and formulation optimization,analysis and determination by the number of viable bacteria,OD₆₀₀value,GABA content detected by high performance liquid chromatography and the calculation of strain survival rate.conclusion as below:1.Screening of fermentation basic medium for GABA-producing strain S33-32.Taking the GABA-producing strain S33-32 as the object,through the 48-hour fermentation culture of MRS,TYG,GYP,LBS,and M17 liquid medium,the density of the bacterial solution OD₆₀₀was measured,and the quantitative analysis of GABA obtained:When using the M17 medium,the bacteria The OD₆₀₀value of the liquid density was 1.274±0.036,and the GABA content was0.1227±0.015 mg/m L,which was larger than other media.Therefore,the M17 medium was determined to be the basic medium for the GABA-producing strain S33-32.2.The changing law of GABA-producing strain S33-32.Taking the GABA-producing strain S33-32 as the research object,using the M17 liquid medium to ferment and culture,plot the GABA-producing strain S33-32 with the fermentation time.The logarithmic growth period is 4-8h,and the relationship between the three curves has a certain correlation.With the extension of the fermentation time,the OD₆₀₀,the number of viable bacteria and the GABA production also increase accordingly.3.Optimization of high-density culture medium for GABA-producing strain S33-32.The GABA-producing strain S33-32 was used as the object of fermentation and cultivation,and the optimal GABA-producing medium M17 medium was optimized and improved.Through single factor test and response surface optimization test,it was determined that M17 was used as the basic medium and the only carbon The source sucrose is added at 0.5%,the compound nitrogen source(whey powder:beef extract:soy peptone=1:1:2)is at 2.0%,L-glutamate is at 1.0%,and the fermentation time is 48h.,The other ingredients remain unchanged.Under these conditions,the number of viable cells of the GABA-producing strain S33-32 was 6.132×10⁸CFU/m L,and the GABA content in the fermentation broth was 0.1896±0.004 mg/m L.4.Optimization of high-density culture conditions for GABA-producing strain S33-32.For the GABA-producing strain S33-32 as the object of fermentation and culture,the optimal GABA-producing medium M17 optimized medium screened in the previous period is based on the single factor test and response surface optimization test to determine the best fermentation of the GABA-producing strain S33-32 Culture conditions:the inoculum was 3.0%,the initial p H of the fermentation broth was 6.80,the fermentation culture temperature was 35°C,and the fermentation time was 46 h.Under these conditions,the number of viable cells of the GABA-producing strain S33-32 was 9.67×10⁸CFU/m L,and the GABA content in the fermentation broth was 0.2204±0.015 mg/m L.5.The selection of GABA-producing strain S33-32 starter to prepare vacuum freeze-dried protective agent.Taking the GABA-producing strain S33-32 as the test object,the best GABA-producing medium M17 selected in the previous period,the optimized medium composition and the best fermentation conditions were used for high-density fermentation and cultivation to prepare bacterial slime,through single-factor experiments and responses Based on optimization tests,it was determined that GABA-producing strain S33-32 starter preparation protective agent composition and addition ratio were:skimmed milk addition amount was 12%,glycerin addition amount was 0.8%,lactose addition amount was 9%,and ascorbic acid addition amount was 1%.Under these conditions,the GABA-producing strain S33-32 starter was prepared with a freeze-dried viable cell count of 1.73×10⁹CFU/g,and the survival rate was 53.2%.