Transcriptome analysis reveals the mechanism underlying improved glutathione biosynthesis and secretion in Candida utilis during selenium enrichment

The effect of sodium selenite on batch culture of Candida utilis CCTCC M 209298 was investigated. Cell growth was inhibited while glutathione biosynthesis and secretion were improved during selenium enrichment. To reveal the mechanism underlying the decrease in biomass and the increase in glutathione, both metabolic flux analysis of key intermediates involved in glutathione metabolic pathway and transcriptome analysis of C. utilis by RNA-seq were carried out for selenized cells and the control without selenium enrichment. Results indicated that sodium selenite decreased carbon fluxes towards biomass but increased fluxes towards amino acids for the biosynthesis of glutathione and related amino acids. Selenium enrichment down-regulated a large number of genes involved in cell components and the cell cycle, resulting in decreased biomass as well as increased cell permeability. Moreover, several genes associated with transportation, binding, and mitochondrial and ribosomal functions for energy metabolism and protein synthesis were up-regulated in the presence of sodium selenite. All of these results disclosed the physiological response of C. utilis to sodium selenite.