ADVANCED-CORN PROCESSING TECHNOLOGY AND SYSTEMATIC ENGINEERING - -ISOLATION OF HIGH-YIELD STRAINS AND CONDITION OPTIMIZATION OF CORN L-LACTIC ACID FERMENTATION

摘要

From primary isolation among 28 strains belong to different genera, one strain (Lactobacillus casei CSN0041, named Lcr), which yielded chiral L-lactic acid with high purity (>90%), was isolated. Started with Lcr treated with UV light, diacetyl sulfate, and UV light plus diacetyl sulfate, a new thermophilic mutant, called HT, was obtained, which raised the L-lactic acid production by 22.3%. For this mutant, the optimal conditions for L-lactic acid growth and fermentation in HT are: growth temperature28°C, fermentation temperature 46°C, fermentation pH 6.5 ±0.1. By orthogonal design, the optimal fermentation medium contains 5% hydrolyzed corn sugar, 3% wheat roots, 1% K_2HPO_4, 1.2% powder of deoiled soybean cake, 5% CaC03. Under the optimized conditions, after 4 day fermentation the medium contained: less than Ig/L of the reduced sugar, 43.02 g/L of L-lactic acid, with a conversion rate of 92.6%, was found in the liquid fermentation medium.