title: Metabolism and secretion of yellow pigment under high glucose stress with Monascus ruber.
abstract: The biosynthesis of microbial secondary metabolites is induced by a wide range of environmental stresses. In this study, submerged fermentation of Monascus yellow pigments by Monascus ruber CGMCC 10910 under high glucose stress was investigated. The increase of lipid content was the major contributor to the increase of dry cell weight (DCW), and the lipid-free DCW was only slightly changed under high glucose stress, which benefited the accumulation of intracellular hydrophobic pigments. The fatty acid composition analysis in Monascus cell membranes showed that high glucose stress significantly increased the ratio of unsaturated/saturated fatty acid and the index of unsaturated fatty acid (IUFA) value, which would improve the fluidity and permeability of the cell membrane. As a consequence, high glucose stress increased extracellular yellow pigments production by enhancing secretion and trans-membrane conversion of intracellular pigments to the broth. The total yield of extracellular and intracellular yellow pigments per unit of lipid-free DCW increased by 94.86 and 26.31% under high glucose stress compared to conventional fermentation, respectively. A real-time quantitative PCR analysis revealed that the expression of the pigment biosynthetic gene cluster was up-regulated under high glucose stress. The gene mppE, which is associated with yellow pigment biosynthesis, was significantly up-regulated. These results  indicated that high glucose stress can shift the Monascus pigment biosynthesis pathway to accumulate yellow pigments and lead to a high yield of both extracellular and intracellular yellow pigments. These findings have potential application in commercial Monascus yellow pigment production.
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Tao
authors.initials: T
authors.lastname: Huang
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Meihua
authors.initials: M
authors.lastname: Wang
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Kan
authors.initials: K
authors.lastname: Shi
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.|Dongguan Tianyi Biotech. Co.Ltd., Dongguan, 523000, People's Republic of China.
authors.forename: Gong
authors.initials: G
authors.lastname: Chen
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006, People's Republic of China.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Tian
authors.affiliation: School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006, People's Republic of China. btzhqwu@scut.edu.cn.
authors.forename: Zhenqiang
authors.identifier: http://orcid.org/0000-0002-8531-4898
authors.initials: Z
authors.lastname: Wu
keywords: Gene expression; High glucose stress; Lipids; Monascus ruber; Pigments secretion; Yellow pigments