Adaptive laboratory evolution of Serratia marcescens with enhanced osmotic stress tolerance for prodigiosin synthesis

Abstract

Prodigiosin, a valuable intracellular secondary metabolite, is produced by Serratia marcescens. However, synthesis during fermentation is constrained by osmotic pressure. In this study, adaptive laboratory evolution was applied to the strain SDSPY-136 to improve osmotic stress tolerance. After 120 passages, screening and validation yielded a strain with high osmotic pressure resistance, S. marcescens R82. The UV absorption spectrum, HPLC peak time, FTIR functional groups, and ¹H NMR chemical shifts revealed that the pigment generated by the evolved strain was prodigiosin. After batch fermentation in a 5 L bioreactor, the prodigiosin concentration was 11.4 g/L, double the initial strain. Transcriptomic analyses revealed significant enrichment for 830 genes. R82 showed alterations in various pathways, indicating that the regulation of intracellular metabolic pathways promoted the availability of prodigiosin precursors, increasing the capacity for prodigiosin synthesis and extracellular release. This study clarifies the molecular evolution mechanism and presents a novel approach for improving yields in S. marcescens.