Investigation of the mycelial morphology of Monascus and the expression of pigment biosynthetic genes in high-salt-stress fermentation

The effects of environmental factors on the synthesis of water-soluble Monascus red pigments via submerged fermentation: a review

Monascus pigments (MPs) have been used as natural food pigments for many years. There is a high demand for Monascus red pigments (MRPs) to enhance color and for antibacterial and cancer prevention therapies in food and medicine. Most MRPs are not water soluble, and the yield of water-soluble MRPs is naturally low. On the other hand, water-soluble MRP is more cost effective for application in industrial mass production. Therefore, it is important to improve the yield of water-soluble MRPs. Environmental factors have a significant influence on the synthesis of water-soluble MRPs, which is crucial for the development of industrial production of water-soluble MRPs. This review introduces the biosynthetic pathways of water-soluble MRPs and summarizes the effects of environmental factors on the yield of water-soluble MRPs. Acetyl coenzyme A (acetyl-CoA) is a precursor for MPs synthesis. Carbon and nitrogen sources and the carbon/nitrogen ratio can impact MP production by regulating the metabolic pathway of acetyl-CoA. Optimization of fermentation conditions to change the morphology of Monascus can stimulate the synthesis of MPs. The appropriate choice of nitrogen sources and pH values can promote the synthesis of MRPs from MPs. Additives such as metal ions and non-ionic surfactants can affect the fluidity of Monascus cell membrane and promote the transformation of MRPs into water-soluble MRPs. This review will lay the foundation for the industrial production of water-soluble MRPs. © 2024 Society of Chemical Industry.

Mutation Breeding of Monascus to Produce a High Yield of Orange Pigment and Low Citrinin Content Using the ARTP Method

Monascus is a filamentous fungus with a long history of application in China, which can produce a variety of secondary metabolites, including Monascus red pigments, Monascus orange pigments, Monascus yellow pigments, and citrinin. There is widespread attention being paid to natural pigments because of their safety. Among the many natural pigments, orange pigment has a wide range of applications because of its unique color, but current production levels in the orange pigment industry are limited to a certain extent due to the insufficiently wide range of sources and low production. In this study, the ARTP mutation was used to obtain a strain with high-yield orange pigment and low citrinin. The strain RS7 was obtained through two-step mutagenesis, and all three pigments were improved to different degrees. The color value of orange pigment was elevated from the original 108 U/mL to 180 U/mL, an increase of 66.7% compared to the original strain, and the citrinin content was reduced by 69%. The result of microscopic morphology showed that RS7 has more wrinkles and is more convex than the R1 strain, but there was little change between the two strains. Therefore, the ARTP mutation influenced the growth and the biosynthesis of pigments in Monascus. In addition, the conditions of ultrasonic extraction of Monascus pigments were optimized using the response surface, and the separation of pigments was achieved with the method of thin-layer chromatography. Pigment stability results showed that the temperature had no significant effect on orange pigment, while tea polyphenol could improve its stability. This study generated a strain with high-yielding orange pigment and could lay a foundation for the future application of Monascus orange pigment in the food industry.

Obtaining more contaminant-resistant variants from a native Chlorella vulgaris strain

Cildáñez stream (in Matanza-Riachuelo basin, Buenos Aires) is one of the most polluted watercourses of Argentina, containing a mixed contamination from agricultural and industrial wastes. The application of water bioremediation processes for this kind of effluent will require microorganisms with a high tolerance to contamination. In this sense, obtaining higher contaminant-resistant microalgae lines is widely desired. In this study, adaptive laboratory evolution (ALE) and random mutagenesis were used to obtain Chlorella vulgaris LMPA-40 strains adapted to grow in polluted water from the Cildáñez stream. The ALE process was performed by 22 successive subcultures under selective pressure (Cildáñez wastewater alone or with the addition of phenol or H2O2) while random mutagenesis was performed with UV-C radiation at 275nm. Not all the cell lines obtained after ALE could adapt enough to overcome the stress caused by the Cildáñez wastewater, indicating that the process is quite random and depends on the stressor used. The best results were obtained for the Cildáñez wastewater adapted cells (Cild 3 strain) that were more resistant than the original strain. The concentration of protein, Chlorophyll A, Chlorophyll B, and carotenoids in the Cild 3 ALE evolved strain was higher than that of the control strain. However, this strain exhibited half of the lipid content compared to the same control strain. Interestingly, these alterations and the acquired tolerance may be reversed over time during storage. These findings suggest that the acquisition of novel cell lines could not be permanent, a fact that must be considered for future trials.

The colorful fungi of the Chilean forests: Production, chemical characterization and possible applications of their pigments

In Chile, as in the rest of the world, only a small fraction of the fungal diversity inhabiting the wide variety of its ecosystems is known. This diversity must hide an inestimable richness of species with interesting biotechnological potential, including fungal pigment producers. Recently, interest in filamentous fungi has increased significantly due to their importance as alternative sources of pigments and colorants that are environmentally and human health friendly. As a result, fungal pigments are gaining importance in various industrial applications, such as food, textiles, pharmaceuticals, cosmetics, etc. The increasing consumer demand for "green label" natural colorants requires the exploration of different ecosystems in search of new fungal species that are efficient producers of different pigment with a wide range of colors and ideally without the co-production of mycotoxins. However, advances are also needed in pigment production processes through fermentation, scale-up from laboratory to industrial scale, and final product formulation and marketing. In this respect, the journey is still full of challenges for scientists and entrepreneurs. This chapter describes studies on pigment-producing fungi collected in the forests of central-southern Chile. Aspects such as the exploration of potential candidates as sources of extracellular pigments, the optimization of pigment production by submerged fermentation, methods of pigment extraction and purification for subsequent chemical characterization, and formulation (by microencapsulation) for potential cosmetic applications are highlighted. This potential use is due to the outstanding bioactivity of most fungal pigments, making them interesting functional ingredients for many applications. Finally, the use of fungal pigments for textile and spalting applications is discussed.

Regulation of the pigment production by changing Cell morphology and gene expression of Monascus ruber in high-sugar synergistic high-salt stress fermentation

AIMS

Extreme environment of microbial fermentation is the focus of research, which provides new thinking for the production and application of Monascus pigments (MPs). In this work, the high-sugar synergistic high-salt stress fermentation (HSSF) of MPs was investigated.

METHODS AND RESULTS

The Monascus fungus grew well under HSSF conditions with 35 g L-1 NaCl and 150 g L-1 glucose, and the extracellular yellow pigment and intracellular orange pigment yield in HSSF was 98% and 43% higher than that in conventional fermentation, respectively. Moreover, the mycelial morphology was maintained in a better status with more branches and complete surface structure, indicating good biocatalytic activity for pigment synthesis. Four extracellular yellow pigments (Y1, Y2, Y3, and Y4) were transformed into each other, and ratio of the relative content of intracellular orange pigments to yellow pigments (O/Y) significantly (P < 0.05) changed. Moreover, the ratio of unsaturated fatty acids to saturated fatty acids (unsaturated/saturated) was significantly (P < 0.05) increased, indicating that the metabolism and secretion of intracellular and extracellular pigment might be regulated in HSSF. The pigment biosynthesis genes mppB, mppC, mppD, MpPKS5, and MpFasB2 were up-regulated, whereas the genes mppR1, mppR2, and mppE were down-regulated, suggesting that the gene expression to regulate pigment biosynthesis might be a dynamic change process in HSSF.

CONCLUSIONS

The HSSF system of MPs is successfully performed to improve the pigment yields. Mycelial morphology is varied to enhanced pigment secretion, and gene expression is dynamically regulated to promote pigment accumulation in HSSF.

The hidden rainbow: the extensive biotechnological potential of Antarctic fungi pigments

The Antarctic continent is an extreme environment recognized mainly by its subzero temperatures. Fungi are ubiquitous microorganisms that stand out even among Antarctic organisms, primarily due to secondary metabolites production with several biological activities. Pigments are examples of such metabolites, which mainly occur in response to hostile conditions. Various pigmented fungi have been isolated from the Antarctic continent, living in the soil, sedimentary rocks, snow, water, associated with lichens, mosses, rhizospheres, and zooplankton. Physicochemical extreme environments provide a suitable setup for microbial pigment production with unique characteristics. The biotechnological potential of extremophiles, combined with concerns over synthetic pigments, has led to a great interest in natural pigment alternatives. Besides biological activities provided by fungal pigments for surviving in extreme environments (e.g., photoprotection, antioxidant activity, and stress resistance), it may present an opportunity for biotechnological industries. This paper reviews the biotechnological potential of Antarctic fungal pigments, with a detailed discussion over the biological role of fungal pigments, potential industrial production of pigments from extremophilic fungi, pigments toxicity, current market perspective and published intellectual properties related to pigmented Antarctic fungi.

Comparative Transcriptomic and Metabolomic Analyses Reveal the Regulatory Effect and Mechanism of Tea Extracts on the Biosynthesis of Monascus Pigments

Monascus pigments (MPs) are natural edible pigments with high safety and strong function, which have been widely used in food and health products. In this study, different types of tea extracts (rich in polyphenols) were used to regulate the biosynthesis of MPs. The results showed that 15% ethanol extract of pu-erh tea (T11) could significantly increase MPs production in liquid fermentation of Monaco's purpureus M3. Comparative transcriptomic and metabolomic analyses combined with reverse transcription-quantitative polymerase chain reaction (RT-qPCR) were used to further explore the regulatory mechanism of T11 on the biosynthesis of MPs. Comparative transcriptomic analysis showed that there were 1503 differentially expressed genes (DEGs) between the Con group and the T11 group, which were mainly distributed in carbohydrate metabolism, amino acid metabolism, energy metabolism, lipid metabolism, metabolism of terpenoids and polyketides, etc. A total of 115 differential metabolites (DMs) identified by metabolomics between the Con and T11 groups were mainly enriched in glutathione metabolism, starch and sucrose metabolism, alanine, aspartic acid and glutamate metabolism and glycine, serine and threonine metabolism, etc. The results of metabolomics were basically consistent with those of gene transcriptomics, indicating that the regulatory effect of T11 on the biosynthesis of MPs is mainly achieved through affecting the primary metabolic pathway, providing sufficient energy and more biosynthetic precursors for secondary metabolism. In this study, tea extracts with low economic value and easy access were used as promoters of MPs biosynthesis, which may be conducive to the application of MPs in large-scale industrial production. At the same time, a more systematic understanding of the molecular regulatory mechanism of Monascus metabolism was obtained through multi-omics analysis.

Salt and Metal Tolerance Involves Formation of Guttation Droplets in Species of the Aspergillus versicolor Complex

Three strains of the Aspergillus versicolor complex were isolated from a salty marsh at a former uranium mining site in Thuringia, Germany. The strains from a metal-rich environment were not only highly salt tolerant (up to 20% NaCl), but at the same time could sustain elevated Cs and Sr (both up to 100 mM) concentrations as well as other (heavy) metals present in the environment. During growth experiments when screening for differential cell morphology, the occurrence of guttation droplets was observed, specifically when elevated Sr concentrations of 25 mM were present in the media. To analyze the potential of metal tolerance being promoted by these excretions, proteomics and metabolomics of guttation droplets were performed. Indeed, proteins involved in up-regulated metabolic activities as well as in stress responses were identified. The metabolome verified the presence of amino sugars, glucose homeostasis-regulating substances, abscisic acid and bioactive alkaloids, flavones and quinones.

Analysis of secondary metabolite gene clusters and chitin biosynthesis pathways of Monascus purpureus with high production of pigment and citrinin based on whole-genome sequencing

Monascus is a filamentous fungus that is widely used for producing Monascus pigments in the food industry in Southeast Asia. While the development of bioinformatics has helped elucidate the molecular mechanism underlying metabolic engineering of secondary metabolite biosynthesis, the biological information on the metabolic engineering of the morphology of Monascus remains unclear. In this study, the whole genome of M. purpureus CSU-M183 strain was sequenced using combined single-molecule real-time DNA sequencing and next-generation sequencing platforms. The length of the genome assembly was 23.75 Mb in size with a GC content of 49.13%, 69 genomic contigs and encoded 7305 putative predicted genes. In addition, we identified the secondary metabolite biosynthetic gene clusters and the chitin synthesis pathway in the genome of the high pigment-producing M. purpureus CSU-M183 strain. Furthermore, it is shown that the expression levels of most Monascus pigment and citrinin clusters located genes were significantly enhanced via atmospheric room temperature plasma mutagenesis. The results provide a basis for understanding the secondary metabolite biosynthesis, and constructing the metabolic engineering of the morphology of Monascus.

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.

Transcriptome analysis revealing molecular mechanisms of enhanced pigment yield by succinic acid and fluconazole

This study aimed to elucidate the molecular mechanisms through which succinic acid and fluconazole stimulate Monascus pigment biosynthesis under liquid fermentation conditions. The pigment yield was significantly improved by adding 0.35 g·L^-1 succinic acid or 1.5 g·L^-1 fluconazole. Transcriptome sequencing and RT-qPCR confirmation were performed to reveal transcriptome changes. The results indicated that the addition of succinic acid significantly decreased mRNA expression of genes involved in fatty acid biosynthesis while increasing expression of genes involved in pyruvate metabolism. Fluconazole significantly down-regulated transcripts involved in branched-chain amino acid metabolism, fatty acid metabolism, glycolysis/gluconeogenesis, and pyruvate metabolism, as well as the generation of acetyl-CoA for pigment biosynthesis. On the other hand, nitrogen metabolism and lysine degradation pathways were significantly enriched, which could stimulate the generation of acetyl-CoA. Therefore, the mechanism for enhancing pigment yield may be attributed to the competitive regulation of metabolic pathways toward acetyl-CoA biosynthesis. Additionally, up-regulation of some different key genes in the presence of fluconazole or succinic acid was involved in improving pigment production. This study deepens the theoretical understanding for enhancing pigment biosynthesis and provides a few potential approaches for improving pigment yield.

Comparative metabolomics analysis reveals the metabolic regulation mechanism of yellow pigment overproduction by Monascus using ammonium chloride as a nitrogen source

Monascus yellow pigments (MYPs), as food colorants, are of great interest to the food industry, because of their beneficial biological activities. In this study, a comparative metabolomics strategy revealed the metabolic regulatory mechanism of MYP overproduction, comparing ammonium chloride with peptone as nitrogen sources. Metabolomics-based multivariate regression modeling showed that metabolic biomarkers/modules, such as glucose, lactate, and the pentose phosphate (PP) pathway, were closely associated with the biosynthesis of MYPs. Exogenous addition of glucose increased production of MYPs, whereas lactate reduced it. Inhibition of the PP pathway with dehydroepiandrosterone decreased MYP production, while increasing the shunting production of orange and red pigments. All these treatments significantly changed the expression profiles of the pigment biosynthetic gene cluster and the mycelial morphology. Overall, this study demonstrates the feasibility of elucidating the mechanism of MYP biosynthesis by comprehensive metabolomics analysis, as well as discovering potential engineering targets of efficiency improvements to commercial MYP production. KEY POINTS: • Comparative metabolomics revealed the biomarkers/modules of MYP production. • A rational exogenously adding strategy was implemented to regulate MYP synthesis. • Expression profiles of gene cluster and mycelial morphology were characterized.

Recent Findings in Azaphilone Pigments

Filamentous fungi are known to biosynthesize an extraordinary range of azaphilones pigments with structural diversity and advantages over vegetal-derived colored natural products such agile and simple cultivation in the lab, acceptance of low-cost substrates, speed yield improvement, and ease of downstream processing. Modern genetic engineering allows industrial production, providing pigments with higher thermostability, water-solubility, and promising bioactivities combined with ecological functions. This review, covering the literature from 2020 onwards, focuses on the state-of-the-art of azaphilone dyes, the global market scenario, new compounds isolated in the period with respective biological activities, and biosynthetic pathways. Furthermore, we discussed the innovations of azaphilone cultivation and extraction techniques, as well as in yield improvement and scale-up. Potential applications in the food, cosmetic, pharmaceutical, and textile industries were also explored.

Toward improvements for enhancement the productivity and color value of Monascus pigments: a critical review with recent updates

Monascus pigments are a kind of high-quality natural edible pigments fermented by Monascus filamentous fungi, which have been widely used in food, cosmetics, medicine, textiles, dyes and chemical industries as active functional ingredients. Moreover, Monascus pigments have a good application prospect because of a variety of biological functions such as antibacterial, antioxidation, anti-inflammatory, regulating cholesterol, and anti-cancer. However, the low productivity and color value of pigments restrict their development and application. In this review, we introduced the categories, structures, biosynthesis and functions of Monascus pigments, and summarized the current methods for improving the productivity and color value of pigments, including screening and mutagenesis of strains, optimization of fermentation conditions, immobilized fermentation, mixed fermentation, additives, gene knockout and overexpression technologies, which will help to develop the foundation for the industrial production of Monascus pigments.

Colors of life: a review on fungal pigments

Colorants find social and commercial applications in cosmetics, food, pharmaceuticals, textiles, and other industrial sectors. Among the available options, chemically synthesized colorants are popular due to their low-cost and flexible production modes, but health and environmental concerns have encouraged the valorization of biopigments that are natural and ecofriendly. Among natural biopigment producers, microorganisms are noteworthy for their all-seasonal production of stable and low-cost pigments with high-yield titers. Fungi are paramount sources of natural pigments. They occupy diverse ecological niches with adaptive metabolisms and biocatalytic pathways, making them entities with an industrial interest. Industrially important biopigments like carotenoids, melanins, riboflavins, azaphilones, and quinones produced by filamentous fungi are described within the context of this review. Most recent information about fungal pigment characteristics, biochemical production routes and pathways, potential applications, limitations, and future research perspectives are described.

Increases of Lipophilic Antioxidants and Anticancer Activity of Coix Seed Fermented by Monascus purpureus

Lipophilic tocols, γ-oryzanol, and coixenolide in coix seed before and after fermentation by Monascus purpureus were determined. Antioxidant and anticancer activities of raw and fermented coix seed were evaluated using free-radical-scavenging assays and polyunsaturated fatty acid oxidation model, and human laryngeal carcinoma cell HEp2, respectively. Compared to the raw seed, the tocols, γ-oryzanol, and coixenolide contents increased approximately 4, 25, and 2 times, respectively, in the fermented coix seed. Especially, γ-tocotrienol and γ-oryzanol reached 72.5 and 655.0 μg/g in the fermented coix seed. The lipophilic extract from fermented coix seed exhibited higher antioxidant activity in scavenging free radicals and inhibiting lipid oxidation. The inhibitory concentrations for 50% cell survival (IC₅₀) of lipophilic extract from fermented coix seed in inhibiting HEp2 cells decreased by 42%. This study showed that coix seed fermented by M. purpureus increased free and readily bioavailable lipophilic antioxidants and anticancer activity. Therefore, fermentation could enhance the efficacy of the health promoting function of coix seeds.

Additional moisture during koji preparation contributes to the pigment production of red koji (Monascus-fermented rice) by influencing gene expression

Additional moisture in preparing red koji, Monascus-fermented rice, is a characteristic production process. To determine how additional moisture affects red koji preparation as per quality, we compared the growth of Monascus purpureus, enzyme and pigment production, and related gene expressions using our findings. We considered two kinds of red koji: one prepared with additional moisture at the middle part of the preparation and the other prepared without additional moisture. Our results showed that additional moisture did not promote the growth of M. purpureus, but it was significantly increased the pigment (red and yellow) and tended to increase the α-amylase level and saccharification power. Although adding a high amount of moisture (approximately 60% moisture content) promoted pigment production, it slightly repressed enzyme production. In contrast, adding approximately 50% moisture content promoted enzyme production. These findings showed that the additional moisture can affect the quality of red koji on the purpose. The expression of 10 pigment biosynthetic gene clusters and two glycohydrolase genes in red koji after adding moisture was analyzed through real-time qPCR. Eight genes were upregulated within 1 hr after adding water, with mppR2 being the first upregulated gene within 30 min. The expression of genes as per pigment production quickly responded to additional moisture during solid-state fermentation. Moreover, acetyl-CoA, which is a starting substrate for pigment content in red koji was increased within 3 hr after adding water. This study first described the relationship between additional moisture and expression of pigment biosynthetic genes by Monascus spp. during red koji preparation.

Biosynthesis of azaphilones: a review

Covering up to 2020 Azaphilones are fungal polyketide pigments bearing a highly oxygenated pyranoquinone bicyclic core; they are receiving a great deal of increasing research interest for their applications in the agroalimentary, dyeing, cosmetic, printing and pharmaceutical industries. Their biosynthetic pathways are not fully elucidated; however, thanks to recent genomic approaches combined with the increasing genome sequencing of fungi, some of these pathways have been recently unveiled. This is the first review on the biosynthesis of azaphilonoids adressed from a genomic point of view.

Improving mycelial morphology and adherent growth as well as metabolism of Monascus yellow pigments using nitrate resources

Mycelial adhesion affects cell growth and the production of water-soluble extracellular yellow pigment (EYP) in submerged fermentation with Monascus ruber CGMCC 10910. Two nitrates, NaNO₃ and KNO₃, were used as nitrogen sources for mitigating mycelial adhesion and improving the production of EYP in this study. The results showed that the adhesion of mycelia in the fermentation broth significantly decreased by adding 5 g/L NaNO₃, which prevented mycelia from attaching to the inner wall of the Erlenmeyer flask. It was suggested that NaNO₃ reduced the total amount of extracellular polysaccharides, increased extracellular proteins, and decreased the viscosity of the fermentation broth. Scanning electron microscopy (SEM) analysis revealed that the mycelial morphology was shorter and more dispersed and vigorous under NaNO₃ conditions than under the control conditions. The biomass increased by 49.2% and 45.4% with 5 g/L NaNO₃ and 6 g/L KNO₃ treatment, respectively, compared with that of the control, and the maximum production of EYP was 267.1 and 241.8 AU₃₅₀, which increased by 70.0% and 53.9% compared with that of the control, respectively. Simultaneously, the ratios of intracellular yellow pigment to orange pigment increased significantly with 5 g/L of NaNO₃ addition (p < 0.05). Genetic analysis found that the expression levels of the key genes for Monascus pigment biosynthesis were significantly upregulated by NaNO₃ addition (p < 0.05 or p < 0.01). This study provides an effective strategy for the production of water-soluble Monascus yellow pigments.Key Points• Nitrate addition decreased mycelial adhesion and improved cell growth in Monascus pigment fermentation.• The biosynthesis genes of water-soluble extracellular yellow pigment (EYP) were upregulated by nitrate addition.• The mycelial morphology was significantly influenced to enhance EYP biosynthesis with nitrate addition.