Optimization of Enrichment Culture Medium and Fermentation Conditions for Streptococcus thermophilus 937
The optimization process for Streptococcus thermophilus 937 involved starting from a chemically defined medium,followed by single-factor experiments,response surface experiments,and orthogonal optimization experiments to refine the culture medium and growth conditions.The experimentally determined optimal culture medium for Streptococcus thermophilus 937 is 20 g/L lactose,16.60%enzymatic skim milk,18.88 g/L soybean oligopeptide,1.69%whey protein powder,10 mmol/L histidine,10 mmol/L isoleucine,5 mmol/L tyrosine,1 mmol/L cysteine,1 mmol/L glutamic acid,2 mg/L nicotinic acid,0.5 g/L ascorbic acid,40 mg/L magnesium chloride,2 mg/L calcium pantothenate,4 mg/L thiamine hydrochloride,and 0.4 g/L calcium chloride.The viable cell density of Streptococcus thermophilus 937 reached 1.75×109 CFU/mL when the initial pH was 6.5,with a 2%inoculum and a fermentation temperature of 39℃.This work achieved low-cost,high-efficiency culture methods for Streptococcus thermophilus 937,and these findings lay a foundation for the development and production of commercial products via Streptococcus thermophilus cultures with high viable cell counts.
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