Transcriptional study of the enhanced ε-poly-L-lysine productivity in culture using glucose and glycerol as a mixed carbon source.

A glucose-glycerol mixed carbon source (MCS) can substantially reduce batch fermentation time and improve ε-poly-L-lysine (ε-PL) productivity, which was of great significance in industrial microbial fermentation. This study aims to disclose the physiological mechanism by transcriptome analyses. In the MCS, the enhancements of gene transcription mainly emerged in central carbon metabolism, L-lysine synthesis as well as cell respiration, and these results were subsequently proved by quantitative real-time PCR assay. Intracellular L-lysine determination and exhaust gas analysis further confirmed the huge precursor L-lysine pool and active cell respiration in the MCS. Interestingly, in the MCS, pls was remarkably up-regulated than those in single carbon sources without transcriptional improvement of HrdD, which indicated that the improved ε-PL productivity was supported by other regulators rather than hrdD. This study exposed the physiological basis of the improved ε-PL productivity in the MCS, which provided references for studies on other biochemicals production using multiple substrates.