Integrative addition of sucrose esters and immobilisation technology for enhancing yellow pigment yield of Monascus purpureus HBSD08 under submerged fermentation conditions and its molecular mechanism

In this study, the production of yellow pigment by Monascus purpureus upon the addition of sucrose esters under submerged fermentation was significantly promoted. When the addition of sucrose esters was integrated with immobilised fermentation using 0.75 g of corn cob as the carrier for 5 days, the yellow pigment yield reached 39.24 AU/50 mL and was 4.12 times that of the control group. Monascus of integrative fermentation under five-batch fermentation gave a higher yellow pigment yield than Monascus under free fermentation. The extracellular production of yellow pigment in the fourth batch reached a maximum value of 56.71 AU/50 mL. Transcriptome analysis revealed that the immobilised fermentation effectively regulated the pyruvate metabolism process, changed the intrinsic components of the cell membrane and the membrane permeability, and improved the transport capacity of pigment across the membrane. The significantly enriched KEGG metabolic pathways revealed that immobilised fermentation enhanced the glycolysis/gluconeogenesis pathway involved in pigment synthesis and altered the metabolic flow. There was an increase in the precursors of yellow pigment synthesis—such as acetyl-CoA, which is produced during tyrosine metabolism—thereby increasing yellow pigment production. This study provides some potential approaches for improving yellow pigment yield whilst also deepening a theoretical understanding of the underpinning mechanisms.