Genetic responses to adding nitrates to improve hydrophilic yellow pigment in Monascus fermentation

Nitrates can stimulate the biosynthesis of hydrophilic yellow pigments (HYPs) in Monascus ruber CGMCC 10910. To explore the molecular mechanisms whereby nitrates (NaNO3 and NH4NO3) regulate HYP production, an integrated transcriptomic and proteomic analysis was conducted in this study. Nitrate addition led to an approximately 75% higher HYP production compared with the untreated group, especially compounds Y3 and Y4. Comparative transcriptomic analysis found that mpigsA, H, K, L, and P genes involved in yellow pigment biosynthesis were significantly upregulated. In addition, pigment biosynthesis-related (carbon catabolism, amino acid metabolism, polyketide synthesis, and fatty acid metabolism) genes were upregulated to provide precursors and energy for HYP biosynthesis and cell growth. Secretion-related (cytomembrane ergosterol biosynthetic, and transport) pathways were also noticeably regulated to accelerate transmembrane transport of HYPs. Meanwhile, proteomic analysis showed that nitrates improved the protein expression of hybrid polyketide synthase-nonribosomal peptide synthetase, oxidoreductase, glucoamylase, endo-1,4-beta-xylanase, O-acetylhomoserine, and isocitrate lyase to enhance HYP production. These findings demonstrated the regulatory mechanism of nitrates for enhancing HYP production in Monascus.

Automated summary

Nitrates can increase the production of hydrophilic yellow pigments in Monascus ruber CGMCC 10910. Through transcriptomic and proteomic analysis, it was found that nitrates upregulate genes involved in yellow pigment biosynthesis and pathways related to pigment biosynthesis, precursor production, and transport. Proteomic analysis also showed that nitrates enhance the expression of proteins involved in HYP production. These findings provide insights into the regulatory mechanism of nitrates in enhancing HYP production in Monascus.