Triton X-100 supplementation regulates growth and secondary metabolite biosynthesis during in-depth extractive fermentation of Monascus purpureus.

Extractive fermentation has been proven to be efficient in enhancing the secretion and production of secondary metabolites in submerged fermentation by Monascus spp., owing to increased cell membrane permeability and resolved product inhibition. In this study, we investigated the regulation effect of Triton X-100 on cell growth and secondary metabolite biosynthesis in submerged fermentation of M. purpureus DK. The results show that the maximum monascus pigments (MPs), citrinin (CIT) production, and specific growth rate are 136.86 U/mL, 4.57 mg/L, and 0.04 h, respectively, when 3 g/L of Triton X-100 is supplemented after fermentation for 10 d, and the extracellular MPs and CIT increased by 127.48% and 288.57%, respectively. RT-qPCR shows that the expression levels of MPs and CIT biosynthesis gene clusters are significantly upregulated, whereas those of glycolysis, tricarboxylic acid cycle, respiratory chains, and ATP synthase are downregulated. This study provides a vital strategy for extractive fermentation under extreme environmental conditions for further enhancing MP production.