Ethanol addition elevates cell respiratory activity and causes overproduction of natural yellow pigments in submerged fermentation of Monascus purpureus

Abstract

In recent years, there has been an increasing demand for natural pigments and Monascus spp. are one of the most important species for pigments production in Asian countries. This study demonstrates a simple but efficient strategy to enhance the production of the yellow pigment from Monascus purpureus. The maximum production of yellow pigments (394 U/mL) was obtained when 3% (v/v) ethanol was added into the medium at the beginning of submerged fermentation (1.59-fold higher than the control group). In addition, CTC staining and ATP measurement were performed to elucidate the potential biological processes involving biomass growth. The changes in the expression level of key genes involved in pigment metabolic pathway indicated that the pigment metabolic pathway was significantly affected by the ethanol addition. Ethanol addition down-regulated MrpigA, MrpigC, MrpigJ, and MrpigK at the first 48 h of the fermentation process and led to more Acetyl-CoA to be used in primary metabolism for biomass accumulation, which was further beneficial for the biosynthesis of yellow pigments. This study has utilized a novel strategy to promote the production of yellow pigments, which also can be applied in other fermentation processes.