Enhanced production of ε-Poly-L-lysine through overexpression of LysR involved in interspecies interactions

Epsilon-poly-L-lysine (ε-PL), an antimicrobial peptide synthesized by Streptomyces albulus through submerged fermentation, is biosynthesized via multiple metabolic pathways. This suggests that global metabolic regulation and interspecies interactions contribute significantly to enhancing ε-PL yield. Current genetic and metabolic engineering strategies, however, primarily aim at strengthening specific metabolic fluxes, without adequately coordinating the diverse physiological requirements involved in ε-PL production. Previous research has shown that interspecies stress induced by Streptomyces gilvosporeus can elicit a broad enhancement of ε-PL biosynthetic pathways. Building on this finding, the present study seeks to identify key transcriptional regulators that respond to such interspecies stress and are capable of systematically improving metabolic efficiency.

Comparative transcriptomic analysis revealed that transcription factors from the RegX3, LysR, and TetR families were significantly upregulated in S. albulus under interspecies stress. Corresponding overexpression strains (OE-RegX3, OE-LysR, OE-TetR1, and OE-TetR2) were constructed using a one-step cloning strategy, all exhibiting altered colony morphology. Among them, OE-LysR showed a 60.9% increase in ε-PL production compared to the wild type in flask cultures. When scaled to a 5-L bioreacter and stimulated with S. gilvosporeus live cells, the ε-PL titer of OE-LysR further rose to 39.6 g/L, marking a 51.1% improvement. Physiological analyses revealed that the enhanced ε-PL production was attributed to the upregulation of key biosynthetic and metabolic pathways.

LysR was identified as a key regulator that mediates interspecies stress from S. gilvosporeus to enhance ε-PL biosynthesis in S. albulus. Overexpression of LysR globally activated ε-PL-related metabolic pathways and markedly increased ε-PL production at both flask and fermenter scales, especially when combined with S. gilvosporeus stimulation. These findings offer new strategies for harnessing interspecies stress to enhance antibiotic fermentation efficiency.