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.Electronic supplementary materialThe online version of this article (doi:10.1186/s13568-017-0382-5) contains supplementary material, which is available to authorized users.

Tracking of pigment accumulation and secretion in extractive fermentation of Monascus anka GIM 3.592

“…Small particles, such as inorganic ions and small organic molecules, can leave the cell via specialized trans-membrane carrier or channel proteins [ 13 ]. Therefore, due to their low molecule weights, intracellular pigments were likely to be taken up and excreted through trans-membrane transport from ion channels in the cell membrane, because the decreased ratio of unsaturated/saturated fatty acid in Monascus anka (Table 2 ) resulted in reduced membrane lipid fluidity [ 36 ].…”

“…Due to the high complexity in the pigment compositions, it is difficult to quantify the composition of each chemical compound in grams or moles. Alternatively, Monascus pigment content is generally demonstrated by their integrated color characteristics through the visible spectrum and the visible absorbance at 410 nm for yellow pigments, 470 nm for orange pigments and 510 nm for red pigments [ 4 , 8 , 10 , 11 , 14 – 16 , 19 , 21 , 26 , 36 , 43 – 46 ]. Additionally, the total pigment yield was defined as the yields of intracellular pigments plus extracellular pigments.…”

“…The biomass characteristic to dry cell weight (DCW) was determined by drying the mycelia at 60 °C until a constant weight was achieved. Additionally, the estimation of lipid content followed the same method as described by Huang et al [ 36 ].…”

“…After cultivation for 6 days, the batch fermentation broth was added to 40 g/L Triton X-100 for extractive cultivation (EC) at 30 °C with 180 rpm for 1 h. Then, 25 mL of broth was withdrawn from batch fermentation (BF), extractive cultivation (EC), and extractive fermentation (EF), respectively, to collect mycelia to extract, purify and methylate the cell membrane fatty acids according to the method described by Wang et al [ 19 ]. The fatty acid composition was analyzed using the gas chromatography-mass spectrometry (GC–MS) method described by Huang et al [ 36 ].…”

Effect of initial pH, different nitrogen sources, and cultivation time on the production of yellow or orange Monascus purpureus pigments and the mycotoxin citrinin

“…In an older study (Chen & Johns, ), ankaflavin production was inhibited by using nitrate as a nitrogen source; this was not confirmed in our study. However, in a study performed with Monascus ruber (Huang et al, ) under very similar culture conditions using ammonium sulfate as a nitrogen source, the concentration of monascin was higher than that of ankaflavin. The pH value of 2.5 was found to be optimal for yellow pigment formation by Monascus spp.…”