Breeding and Characterization of a Thermotolerant and High-yield Lactobacillus rhamnosus for L-Lactic acid Production

By UV mutagenesis,a high-yield and thermostable L-lactic acid mutant strain-GX-6 was originally obtained from Lactobacillus rhamnosus JCM1553.At 47℃,the maximum L-lactic acid yield of GX-6 in glucose was 117g/L for 56h,which was 17% higher than that of the original strain(100g/L),with a conversation rate of 68.8 %.The maximum L-lactic acid yield was 138g/L for 72h under the same condition in cassava starch,77.6% higher than that of the original strain(73g/L) and the conversation rate reached to 85.4%.After subculture for 16 generations,the L-lactic acid production capacity of GX-6 remains unchanged,indicating that the mutant is stable.