Optimization of Enrichment Culture Medium and Fermentation Conditions for Streptococcus thermophilus 937
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Abstract:
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, highefficiency 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.
