Multiplex metabolic pathway engineering of Monascus pilosus enhances lovastatin production

Monascus sp. is an important food microbial resource with the production of cholesterol-lowering agent lovastatin and other healthy metabolites. However, the mycotoxin citrinin naturally produced by Monascus sp. and the insufficient productivity of lovastatin limit its large-scale use in food industry. The aim of this paper is to modify a lovastatin-producing strain Monascus pilosus GN-01 through metabolic engineering to obtain a citrinin-free M. pilosus strain with higher yield of lovastatin. The citrinin synthesis regulator gene ctnR was firstly disrupted to obtain GN-02 without citrinin production. Based on that, the lovastatin biosynthesis genes (mokC, mokD, mokE, mokF, mokH, mokI, and LaeA) were, respectively, overexpressed, and pigment-regulatory gene (pigR) was knocked out to improve lovastatin production. The results indicated ctnR inactivation effectively disrupted the citrinin release by M. pilosus GN-01. The overexpression of lovastatin biosynthesis genes and pigR knockout could lead higher contents of lovastatin, of which pigR knockout strain achieved 76.60% increase in the yield of lovastatin compared to GN-02. These studies suggest that such multiplex metabolic pathway engineering in M. pilosus GN-01 is promising for high lovastatin production by a safe strain for application in Monascus-related food. KEY POINTS: • Disruption of the regulator gene ctnR inhibited citrinin production of M. pilosus. • Synchronous overexpression of biosynthesis gene enhanced lovastatin production. • pigR knockout enhanced lovastatin of ΔctnR strain of M. pilosus.

Monascus pilosus YX-1125: An efficient digester for directly treating ultra-high-strength liquor wastewater and producing short-chain fatty acids under multiple-stress conditions

Ultra-high-strength liquor wastewater (UHS-LWW) is rich in organic matter, and the required treatment is expensive. Here, an extremophilic strain Monascus pilosus YX-1125 was isolated for the direct conversion of UHS-LWW to short-chain fatty acids (SCFAs). Strain YX-1125 is an efficient SCFA producer with carbohydrate metabolic flexibility under multiple-stress conditions. Moreover, strain YX-1125 could tolerate up to 75 g/L, 100 g/L, and 50 g/L of ethanol, organic acids, and salt, respectively, without inhibition. In repeated-cycle fermentations, 17.8 g/L of butyric acid and 2.0 g/L of propionic acid were produced from UHS-LWW at the fifth cycle, which are the highest concentrations of wastewater-derived SCFAs reported to date. After SCFA recovery, a 98.9% COD reduction was achieved, which is estimated to reduce treatment costs by 91.7%. Results indicate that M. pilosus YX-1125 is a promising strain for the direct treatment of UHS-LWW, and for converting it into valuable biochemicals without any pre-treatment.

Production of Monacolin K in Monascus pilosus: Comparison between Industrial Strains and Analysis of Its Gene Clusters

Monascus pilosus strains are widely applied to yield a cholesterol synthesis inhibitor monacolin K (MK), also called lovastatin (LOV). However, the mechanism of MK production by M. pilosus strains is still unclear. In this study, we firstly confirmed four Monascus strains, MS-1, YDJ-1, YDJ-2, and K104061, isolated from commercial MK products as M. pilosus and compared their abilities to produce MK in solid-state and liquid-state cultures. Then, we sequenced and analyzed their genomes and MK biosynthetic gene clusters (BGCs). The results revealed that the MK yields of MS-1, YDJ-1, YDJ-2, and K104061 in solid-state cultures at 14 days were 6.13, 2.03, 1.72, and 0.76 mg/g, respectively; the intracellular and extracellular MK contents of MS-1, YDJ-1, YDJ-2, and K104061 in liquid-state cultures at 14 days reached 0.9 and 1.8 mg/g, 0.38 and 0.43 mg/g, 0.30 and 0.42 mg/g, and 0.31 and 0.76 mg/g, respectively. The genome sizes of the four M. pilosus strains were about 26 Mb, containing about 7000-8000 coding genes and one MK gene cluster. The MK BGCs of MS-1, YDJ-2, and K104061 contained 11 genes, and the MK BGC of YDJ-1 contained 9 genes. According to the literature search, there are few comparisons of gene clusters and related genes responsible for the synthesis of LOV and MK. We also compared the LOV BGC in A. terreus with the MK BGCs in different species of Monascus spp., and the results revealed that although LOV and MK were the same substance, the genes responsible for the synthesis of MK were much less than those for LOV synthesis, and the gene functions were quite different. The current results laid a foundation to explore the mechanism of MK produced by Monascus spp. and compare the synthesis of LOV and MK.

A Monascus pilosus MS-1 strain with high-yield monacolin K but no citrinin

Monacolin K (MK) produced by Monascus spp. is mostly used to regulate cholesterol level, while it can be contaminated by citrinin, a mycotoxin yielded by some Monascus strains. To develop production of citrinin-free MK, an M. sp. MS-1 strain, identified as M. pilosus by morphologies and internal transcribed spacer sequences analysis, was isolated from red fermented rice. After 14 days of fermentation, yields of citrinin-free MK could be up to 0.58 mg/mL and 16.45 mg/g in liquid- and solidstate fermentation products under optimal conditions, respectively. Further determination revealed that no citrinin biosynthesis related genes such as ctnA, pksCT, ctnE, and ctnR were detected. Thus, HPLC combined with citrinin-related gene analyses can be used for rapid screening of non-citrinin production Monascus strains.

Merrill) on high-fat diet-induced obesity

The purpose of this study was to examine the antiobesity effects of Monascus pilosus-fermented black soybean (F-BS) in C57BL/6 mice with high-fat diet (HFD)-induced obesity. F-BS (oral, 0.5 and 1.0 g/kg per body weight, twice per day) ameliorated obesity by reducing body and liver weight increases, and regulating blood glucose and cholesterol levels in C57BL/6 mice fed a control or HFD with oral administration of F-BS for 12 weeks. F-BS suppressed the growth of epididymal, retroperitoneal, and perirenal fat pads by preventing increases in the adipocyte size. Moreover, the levels of blood glucose, total cholesterol, and leptin were significantly lowered by F-BS administration in a dose-dependent manner. These results indicated that F-BS is a beneficial food supplement for preventing obesity, controlling blood glucose, and lowering cholesterol. Future research strategies should address the mechanisms that selectively regulate obesity, including hyperglycemia and hypercholesterolemia.

Quality Characteristics and Content of Polysaccharides in Green Tea Fermented by Monascus pilosus

In this study, we designed a method to manufacture elevated fermented green tea by using Monascus pilosus, which is known as a functional microbe, and observe its antioxidant abilities and quality characteristics. The water-soluble substance (WSS) content of the fermented tea by M. pilosus (FTM) was lower than that of the non-fermented tea (NFT), although the alcohol-insoluble substance (AIS) content of the FTM was higher than that of NTM. On the other hand, the fractionated distilled water-soluble polysaccharide (DWSP), CDTA-soluble polysaccharides (CDSP), sodium carbonate-soluble polysaccharide (SCSP) and KOH soluble hemicellulose (HC) obtained from the AIS of the FTM was markedly higher than that of NFT. In the antioxidant parameters, the electron donating ability of all fractions, except HC, extracted from FTM was higher than that of NFT, and iron chelating ability of all fractions, except CDSP, extracted from FTM was higher than that of NFT. Whereas the DWSP and SCSP obtained from the FTM were higher than that of NFT, the activity of the HC fraction from both NFT and the FTM could not be detected. In addition, the xanthin oxidase (XO) inhibitory activities of the DWSP, CDSP and the SCSP obtained from the NFT were significantly higher than that of FTM, the aldehyde oxidase (AO) inhibitory activities of the DWSP and SCSP extracted from the FTM were markedly higher than that of the NFT. Meanwhile, the acceptance of NFT and FTM had no significant difference, while the quality of aroma, taste and mouthfeel of the FTM was higher than that of NFT. These results suggest that the post-fermented tea by Monascus microorgan-isms may be responsible for functional components as well as contribute to the improvement of the tea quality.