Breeding Of Saccharomyces Cerevisiae With High Level Of Mercapto Compound And Optimization Of Its Fermentation Technology

Yeast extract is a multifunctional nutrient flavor enhancer prepared from edible yeast cells.Sulfhydryl compounds have good antioxidant properties,help to scavenge free radicals in the human body,and have various physiological functions such as anti-aging,anti-fatigue,immune enhancement,and elimination of inflammation.At the same time,some amino acids in the thiol compound can react with the food to achieve a flavor and enrich the flavor.The yeast extract made from the sulphur-rich compound Saccharomyces cerevisiae can also have a health-care function while enriching the taste of the seasoning,and will play a huge role in the fields of food,condiments,health products and medicines,and will be the future seasoning.Mainstream research directions in the field of products and health products.In order to improve the intracellular thiol content,this paper carried out research on strain screening,medium optimization,fermentation parameter selection,fermentation feed regulation and so on:1.Comparing the ability of 10 strains of Saccharomyces cerevisiae to produce intracellular thiol compounds,a strain with the highest intracellular thiol compound content,Saccharomyces cerevisiae YC-5,was screened.The medium was optimized on the basis of the initial medium,and the optimized medium composition was determined by single factor experiment and response surface analysis experiment:molasses 70mL/L,yeast dipping powder 5 g/L,peptone 8 g/L,MgSO₄·7H₂O 0.8 g/L,KH₂PO₄ 0.6g/L,and(NH₄)₂SO₄ 0.2 g/L.After verification with a 30 L fermentor,the peak of intracellular thiol content reached 1.81%after optimization of the medium,which was42%higher than 1.27%of the initial medium.2.By studying the effects of fermentation parameters such as initial inoculum size,aeration rate,stirring speed,pH and temperature on the synthesis of intracellular thiol compounds,the optimal fermentation conditions were selected as follows:initial inoculum size was 6%,initial fermenter dry weight was 9 g/L;the aeration rate is 2.5m3/h,the stirring speed is 600 r/min;the pH of 0⁴ h is controlled at about 5.0,and the pH in the fermenter is controlled at 6.0 to 4¹2 h,after 14 h The pH in the fermenter is controlled at 6.5;the temperature is 30°C at 0¹2 h,the temperature is raised to 35°C at 12¹4 h,and the temperature is further raised to 40°C at 14-16 h.Under this fermentation condition,the intracellular thiol content peaked at 2.08%,which was 15%higher than the control tank before optimization.3.In order to further improve the intracellular thiol content of S.cerevisiae strains during fermentation,four different feeding strategies were adopted.They are:only make up ethanol;supplement ethanol and ammonium sulfate at the same time;supplement the ethanol and ammonium sulfate while controlling the pH by adding ammonia water;supplement the ethanol and ammonium sulfate while controlling the pH by adding ammonia water and supplementing H₂O₂ for oxidative stress,induce Synthesis of intracellular thiol compounds.Finally,the optimal feeding strategy was as follows:300mL ethanol was added at 4-8 h,100 g ammonium sulfate was added at 0-10 h(constant to 1000 mL),and 4 mmol/L H₂O₂ was added at 12 h.The pH was controlled with 10%sulfuric acid and 10%ammonia water.Under the optimal feeding strategy,the peak content of intracellular thiol compound reached 2.53%,which was 22%higher than that before feeding.