Rising temperature stimulates the biosynthesis of water-soluble fluorescent yellow pigments and gene expression in Monascus ruber CGMCC10910.

Monascus species can produce secondary metabolites that have a polyketide structure. In this study, four types of extracellular water-soluble yellow pigments (Y1-Y4) were generated by submerged fermentation with Monascus ruber CGMCC 10910, of which Y3 and Y4 had strong yellow fluorescence. The composition of the pigment mixtures was closely related to the fermentation temperature. The dominating pigments changed from Y1 to Y3 and Y4 when fermentation temperature increased from 30 to 35 °C. Increasing the temperature to 35 °C changed the metabolic pathways of the pigments, which inhibited the biosynthesis of Y1 and enhanced the biosynthesis of Y3 and Y4. Moreover, the yield of Y1 reduced insignificantly, while the yields of Y3 and Y4 increased by 98.21 and 79.31% respectively under two-stage temperature fermentation condition. The expression levels of the relative pigment biosynthetic genes, such as MpFasA2, MpFasB2, MpPKS5, mppR1, mppB, and mppE, were up-regulated at 35 °C. The two-stage temperature strategy is a potential method for producing water-soluble Monascus yellow pigments with strong yellow fluorescence.