Promotion of monacolin K production in Monascus extractive fermentation: the variation in fungal morphology and in the expression levels of biosynthetic gene clusters

Surfactant-mediated bio-manufacture: A unique strategy for promoting microbial biochemicals production

Biochemicals are widely used in the medicine and food industries and are more efficient and safer than synthetic chemicals. The amphipathic surfactants can interact with the microorganisms and embed the extracellular metabolites, which induce microbial metabolites secretion and biosynthesis, performing an attractive prospect of promoting the biochemical production. However, the commonness and differences of surfactant-mediated bio-manufacture in various fields are largely unexplored. Accordingly, this review comprehensively summarized the properties of surfactants, different application scenarios of surfactant-meditated bio-manufacture, and the mechanism of surfactants increasing metabolites production. Various biochemical productions such as pigments, amino acids, and alcohols could be enhanced using the cloud point and the micelles of surfactants. Besides, the amphiphilicity of surfactants also promoted the utilization of fermentation substrates, especially lignocellulose and waste sludge, by microorganisms, indirectly increasing the metabolites production. The increase in target metabolites production was attributed to the surfactants changing the permeability and composition of the cell membrane, hence improving the secretion ability of microorganisms. Moreover, surfactants could regulate the energy metabolism, the redox state and metabolic flow in microorganisms, which induced target metabolites synthesis. This review aimed to broaden the application fields of surfactants and provide novel insights into the production of microbial biochemicals.

Histone lysine methyltransferases MpDot1 and MpSet9 are involved in the production of lovastatin and MonAzPs by histone crosstalk modification

Increasing data suggested that histone methylation modification plays an important role in regulating biosynthesis of secondary metabolites (SMs). Monascus spp. have been applied to produce hypolipidemic drug lovastatin (also called monacolin K, MK) and edible Monascus-type azaphilone pigments (MonAzPs). However, little is known about how histone methylation regulates MK and MonAzPs. In this study, we constructed H3K9 methyltransferase deletion strain ΔMpDot1 and H4K20 methyltransferase deletion strain ΔMpSet9 using Monascus pilosus MS-1 as the parent. The result showed that deletion of MpDot1 reduced the production of MK and MonAzPs, and deletion of MpSet9 increased MonAzPs production. Real-time quantitative PCR (RT-qPCR) showed inactivation of mpdot1 and mpset9 disturbed the expression of genes responsible for the biosynthesis of MK and MonAzPs. Western blot suggested that deletion of MpDot1 reduced H3K79me and H4K16ac, and deletion of MpSet9 decreased H4K20me3 and increased H4pan acetylation. Chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) showed ΔMpDot1 strain and ΔMpSet9 strain reduced the enrichment of H3K79me2 and H4K20me3 in the promoter regions of key genes for MK and MonAzPs biosynthesis, respectively. These results suggested that MpDot1 and MpSet9 affected the synthesis of SMs by regulating gene transcription and histone crosstalk, providing alternative approach for regulation of lovastatin and MonAzPs.

Adding genistein or luteolin decreased the yield of citrinin and without reducing pigments in yam solid-fermentation by Monascus

BACKGROUND

Chinese yam fermented by Monascus, namely red mold dioscorea (RMD), has the potential of treating diseases. However, the production of citrinin limits the application of RMD. In the present study, the fermentation process of Monascus was optimized by adding genistein or luteolin to reduce citrinin yield.

RESULTS

The results showed that citrinin in 25 g of Huai Shan yam was reduced by 48% and 72% without affecting the pigment yield by adding 0.2 g of luteolin or genistein, respectively, to a 250-mL conical flask after fermentation for 18 days at 28 °C, whereas the addition of luteolin increased the content of yellow pigment by 1.3-fold. Under optimal conditions, citrinin in 20 g of iron bar yam decreased by 55% and 74% after adding 0.2 g of luteolin or genistein. Luteolin also increased yellow pigment content by 1.2-fold. Ultra HPLC coupled to quadrupole time-of-flight mass spectrometry was used for the preliminary analysis of Monascus fermentation products. It was found that the amino acid types in RMD are similar to those in yams, but there are fewer polysaccharides and fatty acids.

CONCLUSION

The results obtained in the present study showed that the addition of genistein or luteolin could reduce citrinin on the premise of increasing pigment yield, which laid a foundation for the better use of yams in Monascus fermentation. © 2023 Society of Chemical Industry.

Beyond Penicillin: The Potential of Filamentous Fungi for Drug Discovery in the Age of Antibiotic Resistance

Antibiotics are a staple in current medicine for the therapy of infectious diseases. However, their extensive use and misuse, combined with the high adaptability of bacteria, has dangerously increased the incidence of multi-drug-resistant (MDR) bacteria. This makes the treatment of infections challenging, especially when MDR bacteria form biofilms. The most recent antibiotics entering the market have very similar modes of action to the existing ones, so bacteria rapidly catch up to those as well. As such, it is very important to adopt effective measures to avoid the development of antibiotic resistance by pathogenic bacteria, but also to perform bioprospecting of new molecules from diverse sources to expand the arsenal of drugs that are available to fight these infectious bacteria. Filamentous fungi have a large and vastly unexplored secondary metabolome and are rich in bioactive molecules that can be potential novel antimicrobial drugs. Their production can be challenging, as the associated biosynthetic pathways may not be active under standard culture conditions. New techniques involving metabolic and genetic engineering can help boost antibiotic production. This study aims to review the bioprospection of fungi to produce new drugs to face the growing problem of MDR bacteria and biofilm-associated infections.

Linoleic acid functions as a quorum-sensing molecule in Monascus purpureus-Saccharomyces cerevisiae co-culture

When Monascus purpureus was co-cultured with Saccharomyces cerevisiae, we noted significant changes in the secondary metabolism and morphological development of Monascus. In yeast co-culture, although the pH was not different from that of a control, the Monascus mycelial biomass increased during fermentation, and the Monacolin K yield was significantly enhanced (up to 58.87% higher). However, pigment production did not increase. Co-culture with S. cerevisiae significantly increased the expression levels of genes related to Monacolin K production (mokA-mokI), especially mokE, mokF, and mokG. Linoleic acid, that has been implicated in playing a regulating role in the secondary metabolism and morphology of Monascus, was hypothesized to be the effector. Linoleic acid was detected in the co-culture, and its levels changed during fermentation. Addition of linoleic acid increased Monacolin K production and caused similar morphological changes in Monascus spores and mycelia. Exogenous linoleic acid also significantly upregulated the transcription levels of all nine genes involved in the biosynthesis of Monacolin K (up to 69.50% higher), consistent with the enhanced Monacolin K yield. Taken together, our results showed the effect of S. cerevisiae co-culture on M. purpureus and suggested linoleic acid as a specific quorum-sensing molecule in Saccharomyces-Monascus co-culture.

Identification of the high-yield monacolin K strain from Monascus spp. and its submerged fermentation using different medicinal plants

BACKGROUND

Medical plants confer various benefits to human health and their bioconversion through microbial fermentation can increase efficacy, reduce toxicity, conserve resources and produce new chemical components. In this study, the cholesterol-lowering monacolin K genes and content produced by Monascus species were identified. The high-yield monacolin K strain further fermented with various medicinal plants. The antioxidant and anti-inflammatory activities, red pigment and monacolin K content, total phenolic content, and metabolites in the fermented products were analyzed.

RESULTS

Monacolin K was detected in Monascus pilosus (BCRC 38072), and Monascus ruber (BCRC 31533, 31523, 31534, 31535, and 33323). It responded to the highly homologous mokA and mokE genes encoding polyketide synthase and dehydrogenase. The high-yield monacolin K strain, M. ruber BCRC 31535, was used for fermentation with various medicinal plants. A positive relationship between the antioxidant capacity and total phenol content of the fermented products was observed after 60 days of fermentation, and both declined after 120 days of fermentation. By contrast, red pigment and monacolin K accumulated over time during fermentation, and the highest monacolin K content was observed in the fermentation of Glycyrrhiza uralensis, as confirmed by RT-qPCR. Moreover, Monascus-fermented medicinal plants including Paeonia lactiflora, Alpinia oxyphylla, G. uralensis, and rice were not cytotoxic. Only the product of Monascus-fermented G. uralensis significantly exhibited the anti-inflammatory capacity in a dose-dependent manner in lipopolysaccharide-induced Raw264.7 cells. The metabolites of G. uralensis with and without fermentation (60 days) were compared by LC/MS. 2,3-Dihydroxybenzoic acid, 3,4-dihydroxyphenylglycol, and 3-amino-4-hydroxybenzoate were considered to enhance the antioxidant and anti-inflammatory ability.

CONCLUSIONS

Given that highly homologous monacolin K and citrinin genes can be observed in Monascus spp., monacolin K produced by Monascus species without citrinin genes can be detected through the complementary methods of PCR and HPLC. In addition, the optimal fermentation time was important to the acquisition of antioxidants, red pigment and monacolin K. These bioactive substances were significantly affected by medicinal plants over fermentation time. Consequently, Monascus-fermented G. uralensis had a broad spectrum of biological activities.

Effects of mokF gene deletion and overexpression on the Monacolin K metabolism yields of Monascus purpureus

Monascus purpureus is a fungus known for producing various physiologically active secondary metabolites. Of these, Monacolin K, a compound with hypocholesterolemic effects, is controlled by the biosynthetic gene mokF. Here, mokF deletion and overexpression strains (F2 and C3, respectively) were constructed using genetic engineering and compared with the M. purpureus wild strain (M1). The results showed that Monacolin K production was reduced by 50.86% in F2 and increased by 74.19% in C3. Of the three strains, C3 showed the highest production of Monacolin K and the most abnormal morphology. In addition, mokF influenced the expression level of mokA-mokI and might play an important role in regulating the biosynthesis of secondary metabolites in M. purpureus. Overall, our study verified the function of mokF in M. purpureus using gene deletion and overexpression technology. KEY POINTS: • The deletion and overexpression strains of mokF gene were successfully constructed. • The deletion or overexpression of mokF gene directly affected Monacolin K production. •The mokF gene had little effect on Monascus pigments and cell biomass.

Effect of γ-Heptalactone on the Morphology and Production of Monascus Pigments and Monacolin K in Monascus purpureus

Monascus is used widely in Asian countries and produces various biologically active metabolites, such as Monascus pigments (MPs) and monacolin K (MK). In this study, the effect of γ-heptalactone on secondary metabolites and mycelial growth during Monascus purpureus M1 fermentation was investigated. After the addition of 50 μM γ-heptalactone, the yields of MPs (yellow, orange, and red) reached maxima, increased by 115.70, 141.52, and 100.88%, respectively. The 25 μM γ-heptalactone groups showed the highest yield of MK was increased by 62.38% compared with that of the control. Gene expression analysis showed that the relative expression levels of MPs synthesis genes (MpPKS5, MpFasA2, mppB, mppC, mppD, mppG, mpp7, and mppR1/R2) were significantly upregulated after γ-heptalactone treatment. The relative expression levels of MK synthesis genes (mokA, mokC, mokE, mokH, and mokI) were significantly affected. The mycelium samples treated with γ-heptalactone exhibited more folds and swelling than that in the samples of the control group. This study confirmed that the addition of γ-heptalactone has the potential to induce yields of MPs and MK, and promote the expression of biosynthesis genes, which may be related to the transformation of mycelial morphology in M. purpureus.

Triton X-100 supplementation regulates growth and secondary metabolite biosynthesis during in-depth extractive fermentation of Monascus purpureus

Extractive fermentation has been proven to be efficient in enhancing the secretion and production of secondary metabolites in submerged fermentation by Monascus spp., owing to increased cell membrane permeability and resolved product inhibition. In this study, we investigated the regulation effect of Triton X-100 on cell growth and secondary metabolite biosynthesis in submerged fermentation of M. purpureus DK. The results show that the maximum monascus pigments (MPs), citrinin (CIT) production, and specific growth rate are 136.86 U/mL, 4.57 mg/L, and 0.04 h^-1, respectively, when 3 g/L of Triton X-100 is supplemented after fermentation for 10 d, and the extracellular MPs and CIT increased by 127.48% and 288.57%, respectively. RT-qPCR shows that the expression levels of MPs and CIT biosynthesis gene clusters are significantly upregulated, whereas those of glycolysis, tricarboxylic acid cycle, respiratory chains, and ATP synthase are downregulated. This study provides a vital strategy for extractive fermentation under extreme environmental conditions for further enhancing MP production.