Comparative genomics and transcriptome analysis of Lactobacillus rhamnosus ATCC 11443 and the mutant strain SCT-10-10-60 with enhanced L-lactic acid production capacity.

Mechanisms for high L-lactic acid production remain unclear in many bacteria. Lactobacillus rhamnosus SCT-10-10-60 was previously obtained from L. rhamnosus ATCC 11443 via mutagenesis and showed improved L-lactic acid production. In this study, the genomes of strains SCT-10-10-60 and ATCC 11443 were sequenced. Both genomes are a circular chromosome, 2.99 Mb in length with a GC content of approximately 46.8%. Eight split genes were identified in strain SCT-10-10-60, including two LytR family transcriptional regulators, two Rex redox-sensing transcriptional repressors, and four ABC transporters. In total, 60 significantly up-regulated genes (log2 fold-change ≥ 2) and 39 significantly down-regulated genes (log2 fold-change ≤ - 2) were identified by a transcriptome comparison between strains SCT-10-10-60 and ATCC 11443. KEGG pathway enrichment analysis revealed that "pyruvate metabolism" was significantly different (P < 0.05) between the two strains. The split genes and the differentially expressed genes involved in the "pyruvate metabolism" pathway are probably responsible for the increased L-lactic acid production by SCT-10-10-60. The genome and transcriptome sequencing information and comparison of SCT-10-10-60 with ATCC 11443 provide insights into the anabolism of L-lactic acid and a reference for improving L-lactic acid production using genetic engineering.