Integrative Metabolomic and Transcriptomic Analyses Uncover Metabolic Alterations and Pigment Diversity in Monascus in Response to Different Nitrogen Sources

Abstract

Natural MPs containing a mixture of red, orange, and yellow pigments are widely used as food coloring agents. MP diversity provides foods with versatile colors and health benefits but, in turn, complicate efforts to achieve maximum yield or desirable combination of pigments during the manufacturing process.

Metabolomics Analysis Coupled with Weighted Gene Co-Expression Network Analysis Unravels the Associations of Tricarboxylic Acid Cycle-Intermediates with Edible Pigments Produced by Monascus purpureus (Hong Qu)

“…With high levels of reducing equivalents, more ATP were synthesized through oxidative respiratory chain, but interestingly, adding oxaloacetate depressed the intracellular ATP level, which might be due to its shunt flux between TCA and EMP. Additionally, by regulating the TCA cycle, we found that gene expression encoding oxidoreductases in Monascus synthesistic gene cluster changed greatly, but it made little contribution to explaining the production change, possibly because gene cluster expression was not the main limiting factor of pigment synthesis under the conditions used in this study, as described previously [ 21 ].…”

“…However, the stability of production and product quality of MonAzPs is exclusively critical for Monascus fermentation in industry. Until now, numerous factors, including: pH; temperature; carbohydrates; light; and especially nitrogen sources, such as peptone, yeast powder, ammonium chloride, and ammonium nitrate; have been proved to lead to different effects on MonAzPs production [ 21 ], which undoubtedly complicates the investigation of Monascus fermentation. Hence, a simplified and efficient model, such as metabolic perturbation, is necessary to dissect the metabolic mechanism of MonAzPs biosynthesis and regulation, and aid to establish a high-efficient fermentation regulation strategy.…”

“…Despite the fact that MonAzPs are biosynthesized as secondary metabolites in the middle and late stages of Monasucs fermentation, their production is inextricably linked to primary metabolism. Previously, we discovered that the pentose phosphate pathway influenced the synthesis of yellow pigments [ 20 ], and intracellular amino acids influenced the synthesis of red MonAzPs [ 21 ], while orange MonAzPs, as the precursors of yellow and red MonAzPs, were subject to more complex regulation. Because of the diversity of MonAzPs molecules (over a hundred have been found to date), determining that their interaction in biosynthesis is crucial for targeted regulation of specific pigment production.…”

“…Furthermore, uncatalyzed O -to- N substitution reactions with accessible amines in the cell or culture broth can form a wide range of red MonAzPs with a g -vinylogous pyridine core, thus complicating pigment species and yield regulation [ 10 , 17 ]. Therefore, external conditions, such as carbon source [ 18 ], nitrogen source [ 19 , 20 , 21 ], surfactant [ 22 , 23 ], dissolved oxygen [ 24 ], pH [ 25 ], temperature [ 26 ], redox potential [ 27 ], light [ 28 ], and low frequency magnetic field [ 29 ], have considerable impacts on food MonAzPs synthesis by interfering with intracellular metabolism.…”

Comparative Transcriptomic Analysis of Key Genes Involved in Citrinin Biosynthesis in Monascus purpureus

“…Importantly, comparative transcriptomic analyses have been applied to investigate gene transcription in this fungus under different fermentation conditions (such as different carbon/nitrogen sources, special additives, light treatment, etc.) [ 12 , 13 , 14 , 15 ]. These studies often concentrated on the biosynthesis of MPs, although several reports also investigated the expression of the CIT pathway in different M. purpureus strains and fermentation conditions.…”