Exogenous glycine promoted the overproduction of extracellular pigments of Monascus purpureus S109 in submerged fermentation.

The content of extracellular Monascus pigments (eMPs), which has strong functional activity and stability, was improved by adding glycine in previous research. This study systematically elucidated the effects of different glycine concentrations on Monascus purpureus (M. purpureus) S109 eMPs production at both the membrane physiological level and the molecular level of pigment secretion-related gene expression. By measuring the biomass, fatty acid, relative conductivity, fluorescence intensity of tyrosine and tryptophan, membrane potential and ion concentration, coenzyme content, and eMPs content, it was found that 2 g/L glycine could significantly enhance cell membrane fluidity and permeability, and promote the production of eMPs, with their content increasing from 85.82 U/mL to 384.88 U/mL. Under this condition, apart from the negative regulator MrpigI, and the MrpigH directly involved in yellow pigment synthesis, which were down-regulated, all other genes associated with the pigment biosynthesis pathway were significantly up-regulated. Furthermore, the expression of MrpigL and MrpigP genes involved in pigment secretion was significantly up-regulated by 2.8-fold and 10.9-fold, respectively. This study demonstrates that glycine promotes eMPs secretion through modulation of membrane physiological properties and modulation of secretion-related gene expression.