Metabolism and secretion of yellow pigment under high glucose stress with Monascus ruber

Tao Huang,Kan Shi,Meihua Wang,Xiaofei Tian,Zhenqiang Wu,Gong Chen

doi:10.1186/s13568-017-0382-5

Tao Huang, Kan Shi + Show 4 more

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https://doi.org/10.1186/s13568-017-0382-5

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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.

Highlights

Monascus pigments are secondary metabolites with polyketide structures that are produced by Monascus spp. (Feng et al 2012), and are usually classified by color (Patakova 2013)
Production of Monascus pigments and lipids during high glucose stress fermentation The dry cell weight (DCW) of cells takes into account both the accumulation of lipids and lipid-free dry cell weight (LFDCW) accumulation (Wang et al 2015a)
High yields of both extracellular and intracellular yellow pigments were obtained using M. ruber CGMCC 10910 when the initial glucose concentration (IGC) were increased from 50 g/L to >150 g/L

Summary

Introduction

Monascus pigments are secondary metabolites with polyketide structures that are produced by Monascus spp. (Feng et al 2012), and are usually classified by color (yellow, orange or red) (Patakova 2013). Monascus pigments are secondary metabolites with polyketide structures that are produced by Monascus spp. It has long been known that the biosynthesis of microbial secondary metabolites is induced by stress (Ranby 1978). Microorganisms shift from producing primary metabolites to secondary ones in order to preserve energy sources and essential metabolites for more favorable growth conditions. High temperature (>45 °C) can increase the production of Monascus yellow pigments, and a high concentration of sodium chloride inhibited mycelia growth but caused an increase in the production of Monascus red pigments (Babitha et al 2007). Klebsiella oxytoca fermented with a high concentration of molasses exhibited increased production of 2, 3-butanediol (Afschar et al 1991). Increased production of monacolin K was observed when a high

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