Disruption of the Ergosterol Biosynthetic Pathway Results in Increased Membrane Permeability, Causing Overproduction and Secretion of Extracellular Monascus Pigments in Submerged Fermentation

Abstract

Because Monascus pigments (MPs) predominantly accumulate in the cytoplasm during submerged fermentation, many biotechnologies are applied to enhance the production of extracellular MPs (exMPs) to reduce the downstream processing costs. In this study, the genes monascus_7017 and monascus_8018, identified as ERG4 genes, were knocked out to disrupt the ergosterol biosynthetic pathway and enhance the production of exMPs in Monascus purpureus LQ-6. Double-deletion of EGR4 in M. purpureus LQ-6 reduced ergosterol concentration by 57.14% and enhanced exMP production 2.06-fold. In addition, integrated transcriptomic and proteomic analyses were performed to elucidate the transmembrane secretion mechanism of exMPs based on the relationship between ergosterol synthesis and membrane permeability, which revealed that several metabolic pathways were noticeably dynamic, including fatty acid degradation, amino acid metabolism, energy metabolism, carbohydrate metabolism, and transport. These findings therefore clarified the secretion mechanism of exMPs and provide a novel strategy for further enhancement of exMP production in submerged fermentation.

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

“…The omics-based technologies comprising genomics ( 29 , 30 ), transcriptomics ( 30 – 34 ), and proteomics ( 34 ) have been used to identify metabolic mechanisms implicated in carbon starvation stress ( 30 ), exposure to blue light ( 35 ), gene knockout mutants of mga 1–3 ( 32 ), and transmembrane secretion of extracellular MPs ( 34 ) in Monascus strains. These approaches help to elucidate the regulatory mechanisms of MP synthesis and diversity.…”

Analysis of secondary metabolite gene clusters and chitin biosynthesis pathways of Monascus purpureus with high production of pigment and citrinin based on whole-genome sequencing

“…With β-Actin as the reference gene, the genes on the MPs and citrinin gene cluster were selected, and the expression of these genes was detected by qRT-PCR during the submerged fermentation of M. purpureus LQ-6 and M. purpureus CSU-M183, respectively. RT-qPCR was performed according to the method described by Liu et al[21] The primers used in these analyses were listed in Table S1.…”

“…Knocking out the ERG4 gene improved the permeability of the cell membrane and secretion of intracellular pigments; it also changed the morphology of M. purpureus LQ-6 in SF broth. [21] Although many studies on the morphological changes of Monascus in SF have been performed,[22–24] the biological information on the metabolic engineering of Monascus morphology remains unknown.…”

Analysis of secondary metabolite gene clusters and chitin biosynthesis pathways of Monascus purpureus with high production of pigment and citrinin based on whole-genome sequencing

“…Knocking out the ERG4 gene improved the permeability of the cell membrane and secretion of intracellular pigments; it also changed the morphology of M . purpureus LQ-6 in SF broth [ 21 ]. Although numerous studies on the morphological changes of Monascus in SF have been performed, the biological information on the metabolic engineering of morphology of Monascus remains unknown [ 22 – 24 ].…”