Monascus pigments

Enhancing extracellular monascus pigment production in submerged fermentation with engineered microbial consortia

In this study, we investigated the impact of microbial interactions on Monascus pigment (MP) production. We established diverse microbial consortia involving Monascus purpureus and Lactobacillus fermentum. The addition of Lactobacillus fermentum (4% at 48 h) to the submerged fermentation of M. purpureus resulted in a significantly higher MP production compared to that achieved using the single-fermentation system. Co-cultivation with immobilized L. fermentum led to a remarkable increase of 59.18% in extracellular MP production, while mixed fermentation with free L. fermentum caused a significant decrease of 66.93% in intracellular MPs, contrasting with a marginal increase of 4.52% observed during co-cultivation with immobilized L. fermentum and the control group respectively. The findings indicate an evident enhancement in cell membrane permeability of M. purpureus when co-cultivated with immobilized L. fementum. Moreover, integrated transcriptomic and metabolomic analyses were conducted to elucidate the regulatory mechanisms underlying MP biosynthesis and secretion following inoculation with immobilized L. fementum, with specific emphasis on glycolysis, steroid biosynthesis, fatty acid biosynthesis, and energy metabolism.

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.

Analysis of the Anticancer Mechanism of OR3 Pigment from Streptomyces coelicolor JUACT03 Against the Human Hepatoma Cell Line Using a Proteomic Approach

This study assessed OR3 pigment, derived from Streptomyces coelicolor JUACT03, for its anticancer potential on HepG2 liver cancer cells and its safety on HEK293 normal cells. OR3 induced apoptosis and inhibited HepG2 cell proliferation, confirmed by caspase activation, Sub-G1 phase cell cycle arrest, and reduced colony formation. Proteomic analysis revealed altered expression of proteins associated with ribosomal function, mRNA processing, nuclear transport, proteasome activity, carbohydrate metabolism, chaperone function, histone regulation, and vesicle-mediated transport. Downregulation of proteins in MAPKAP kinase1, EIF2, mTOR, and EIF4 pathways contributed to apoptosis and cell cycle arrest. Changes in c-MYC, FUBP1 target proteins and upregulation of Prohibitin-1 (PHB1) were also noted. Western blot analysis supported alterations in eIF2, mTOR, and RAN pathways, including downregulation of RAB 5, c-MYC, p38, MAPK1, and MAPK3. OR3 exhibited significant anti-angiogenic activity in the in ovo CAM assay. In summary, OR3 demonstrated strong anticancer effects, inducing apoptosis, hindering proliferation, and displaying antiangiogenic properties. These findings highlight OR3's potential as an anticancer drug candidate, warranting further in vivo exploration.

Exploring the Subcellular Localization of Monascus Pigments Biosynthases: Preliminary Unraveling of the Compartmentalization Mechanism

Monascus pigments (MPs), a class of secondary metabolites produced by Monascus spp., can be classified into yellow, orange, and red MPs according to their differences in the wavelength of the maximum absorption. However, the biosynthetic sequence and cellular biosynthesis mechanism of different MPs components are still not yet completely clear in Monascus spp. In this study, the subcellular localization of five MPs synthases was investigated using fluorescent protein fusion expression. The results revealed that the proteins encoded by the MPs biosynthetic gene cluster were compartmentalized in various subcellular locations, including the mitochondrial polyketide synthase MrPigA, cytosolic enzymes consisting of the ketoreductase MrPigC, the oxidoreductase MrPigE, and the monooxygenase MrPigN, and the cell-wall-bound oxidoreductase MrPigF. Moreover, the correct localization of MrPigF to the cell wall was crucial for the synthesis of orange MPs. Lastly, we discussed the compartmentalized biosynthetic pathway of MPs. This study will not only be helpful in clarifying the biosynthetic sequence and biosynthesis mechanism of different MPs but also provides new insights into the cellular biosynthesis of secondary metabolites in filamentous fungi.

Expanding the Toolbox for Genetic Manipulation in Pseudogymnoascus: RNAi-Mediated Silencing and CRISPR/Cas9-Mediated Disruption of a Polyketide Synthase Gene Involved in Red Pigment Production in P. verrucosus

Fungi belonging to the genus Pseudogymnoascus have garnered increasing attention in recent years. One of the members of the genus, P. destructans, has been identified as the causal agent of a severe bat disease. Simultaneously, the knowledge of Pseudogymnoascus species has expanded, in parallel with the increased availability of genome sequences. Moreover, Pseudogymnoascus exhibits great potential as a producer of specialized metabolites, displaying a diverse array of biological activities. Despite these significant advancements, the genetic landscape of Pseudogymnoascus remains largely unexplored due to the scarcity of suitable molecular tools for genetic manipulation. In this study, we successfully implemented RNAi-mediated gene silencing and CRISPR/Cas9-mediated disruption in Pseudogymnoascus, using an Antarctic strain of Pseudogymnoascus verrucosus as a model. Both methods were applied to target azpA, a gene involved in red pigment biosynthesis. Silencing of the azpA gene to levels of 90% or higher eliminated red pigment production, resulting in transformants exhibiting a white phenotype. On the other hand, the CRISPR/Cas9 system led to a high percentage (73%) of transformants with a one-nucleotide insertion, thereby inactivating azpA and abolishing red pigment production, resulting in a white phenotype. The successful application of RNAi-mediated gene silencing and CRISPR/Cas9-mediated disruption represents a significant advancement in Pseudogymnoascus research, opening avenues for comprehensive functional genetic investigations within this underexplored fungal genus.

Using stable carbon isotope ratio analysis to detect adulteration in red yeast rice dietary supplements

Red yeast rice (RYR) is marketed as a dietary supplement because it contains natural 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins), including monacolin K. However, there is concern that some RYR supplements may be adulterated with the pharmaceutical drug lovastatin to enhance health claims. We have developed an optimized method to isolate monacolin K/lovastatin from complex RYR dietary supplement matrices to then test for adulteration in RYR supplements using stable carbon isotope (δ13C) analysis. Samples were initially screened for monacolin K/lovastatin using liquid chromatography with mass spectrometric detection (LC-MS). To ensure the extraction process did not affect the measured isotopic values (i.e., isotopic fractionation effects), neat lovastatin standards were spiked into two types of blank RYR matrices (powder and gel). The monacolin K/lovastatin peaks were detected using high performance liquid chromatography with ultraviolet detection (HPLC-UV) and isolated using fraction collection. Residual matrix components were removed from targeted fractions by solid phase extraction (SPE) using graphitized carbon black cartridges. The resulting isolates were then analyzed using elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) to measure δ13C values. The δ13C values of the extracted lovastatin standards were compared to their respective neat lovastatin δ13C values and demonstrated negligible isotopic fractionation effects. Using this optimized clean up method and carbon isotope analysis, thirty-one samples were screened. Eight RYR dietary supplement samples had >0.8 mg/g of monacolin K/lovastatin, our minimum threshold for analyzing samples using this method. Four of these eight samples had δ13C values greater than -28.3‰, a previously proposed cutoff value for natural monacolin K, indicating likely adulteration. Additionally, five RYR powder samples were analyzed as part of a collaborative study using in-house methods from two laboratories and the data shows acceptable agreement in the δ13C values of monacolin K/lovastatin (differences ranging from ±0.02‰ to ±0.76‰). This optimized method represents a robust, reproducible procedure for detecting lovastatin adulteration in dietary supplements with minimal isotopic fractionation.

Mannitol improves Monascus pigment biosynthesis with rice bran as a substrate in Monascus purpureus

To reduce the production cost of Monascus pigments (MPs), the utilization of rice bran (RB), an agricultural waste product, as a substrate in submerged fermentation was conducted in this study. To improve MP production, different nutritional ingredients including mannitol (Man), NH4NO3 (AN), ZnSO4 (Zn), and optimization (Opti), which was a synthesis of the three above ones, were added in rice bran (RB) medium. The yields of MPs, pigment constituents, and growth and development of Monascus purpureus M9 were investigated in this study. Man had the maximum color value of 3,532 U/g, which was 18.69 times more than that of RB and reached up to 76.65% of the value of rice (Rice) fermentation. Man significantly increased the production of two orange pigments, monascorubrin and rubropunctatin, of which the yields were 69.49 and 95.36% of the counterpart of Rice. The biomass and colony diameter of Opti presented the maximum value among different groups. AN and RB induced more asexual spore formation, whereas Opti and Man promoted sexual spore production. Comparative transcriptomic analysis showed that different nutritional ingredients led to changes in pigment production, promoting the growth and development of M. purpureus M9 through the regulation of related gene expression. Man and Opti improved MP production by regulating the primary metabolism, including the Embden-Meyerhof pathway (EMP), the pentose phosphate (PP) pathway, the tricarboxylic (TCA) cycle, fatty acid degradation (FAD), fatty acid biosynthesis (FAB), amino acid metabolism (AAM), and fructose and mannose metabolism (FMM), to provide the precursors (acetyl-CoA and malonyl-CoA) for MP biosynthesis. This study presents a low-cost method for increasing MP production and explains the molecular mechanisms of different nutritional ingredients for enhancing MP biosynthesis.

Microbial Pigments: Major Groups and Industrial Applications

Microbial pigments have many structures and functions with excellent characteristics, such as being biodegradable, non-toxic, and ecologically friendly, constituting an important source of pigments. Industrial production presents a bottleneck in production cost that restricts large-scale commercialization. However, microbial pigments are progressively gaining popularity because of their health advantages. The development of metabolic engineering and cost reduction of the bioprocess using industry by-products opened possibilities for cost and quality improvements in all production phases. We are thus addressing several points related to microbial pigments, including the major classes and structures found, the advantages of use, the biotechnological applications in different industrial sectors, their characteristics, and their impacts on the environment and society.

Growth, morphology, and formation of cinnabarin in Pycnoporus cinnabarinus in relation to different irradiation spectra

BACKGROUND

The demand for natural pigments in general, and for fungi-derived pigments in particular, is constantly rising. Wood-decomposing fungi represent a promising source for natural pigments and they are usually easy to cultivate in pure culture. One of them, i.e., Pycnoporus cinnabarinus, offers a highly interesting spectrum of bioactivity, partly due to the formation of the orange-red pigment cinnabarin. However, apart from a few studies addressing its diverse potential biotechnological applications, there is still a large gap of knowledge concerning the influence of light on the formation of cinnabarin. The aim of this work was to investigate the effect of different irradiations on the cinnabarin content, the growth, and the morphology of three different P. cinnabarinus strains. We used highly standardized irradiation conditions and cultivation techniques in combination with newly developed methods for the extraction and direct quantification of cinnabarin.

RESULTS

Red, green, blue, and UV-A irradiation (mean irradiance Ee = 1.5 ± 0.18 W m-2) had considerable effects on the growth and colony appearance of all three P. cinnabarinus strains tested. The cinnabarin content determined was, thus, dependent on the irradiation wavelength applied, allowing strain-specific thresholds to be defined. Irradiation with wavelengths below this strain-specific threshold corresponded to a lower cinnabarin content, at least at the intensity applied. The orange-red pigment appeared by light microscopy as incrusted extracellular plaques present on the hyphal walls. Highly efficient vegetative propagation occurred by arthroconidia, and we observed the tendency that this asexual reproduction was (i) most frequent in the dark but (ii) never occurred under UV-A exposure.

CONCLUSION

 This study highlights a differential photo-dependence of growth, morphology, and cinnabarin formation in P. cinnabarinus. This confirms that it is advisable to consider the wavelength of the light used in future biotechnological productions of natural pigments.

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.

An efficient method for improving the stability of Monascus pigments using ionic gelation

BACKGROUND

Monascus pigments (Mps) are easily impacted by heating, pH and light, resulting in degradation. In this study, Mps were encapsulated by the ionic gelation method with sodium alginate (SA) and sodium caseinate (SC), as well as CaCl2 as a crosslinker. The encapsulated Mps SA/SC in four proportions (SA/SC: 1/4, 2/3, 3/2, 4/1, w/w). Then, the encapsulation efficiency and particle size of the SA/SC-Mps system were evaluated to obtain the optimal embedding conditions. Finally, the effects of heating, pH, light and storage on the stability of non-capsulated Mps and encapsulated Mps were assessed.

RESULTS

SA/SC = 2/3 (AC2) had higher encapsulation efficiency (74.30%) of Mps and relatively small particle size (2.02 mm). The AC2 gel beads were chosen for further investigating the stability of encapsulated Mps to heating, pH, light and storage. Heat stability experiments showed that the degradation of Mps followed first-order kinetics, and the encapsulated Mps had lower degradation rates than non-capsulated Mps. Encapsulation could reduce the effect of pH on Mps. The effects of ultraviolet light on the stability of Mps were considered, and showed that the retention efficiency of encapsulated Mps was 22.01% higher than that of non-capsulated Mps on the seventh day. Finally, storage stability was also evaluated under dark refrigerated conditions for 30 days, and the results indicated that encapsulation could reduce the degradation of Mps.

CONCLUSION

This study has proved that AC2 gel beads can improve the stability of Mps. Thus, the ionic gelation method is a promising encapsulation method to improve the stability of Mps. © 2023 Society of Chemical Industry.

Histone deacetylase MrHos3 negatively regulates the production of citrinin and pigments in Monascus ruber

Monascus spp. can produce a variety of beneficial metabolites widely used in food and pharmaceutical industries. However, some Monascus species contain the complete gene cluster responsible for citrinin biosynthesis, which raises our concerns about the safety of their fermented products. In this study, the gene Mrhos3, encoding histone deacetylase (HDAC), was deleted to evaluate its effects on the production of mycotoxin (citrinin) and the edible pigments as well as the developmental process of Monascus ruber M7. The results showed that absence of Mrhos3 caused an enhancement of citrinin content by 105.1%, 82.4%, 111.9%, and 95.7% at the 5th, 7th, 9th, and 11th day, respectively. Furthermore, deletion of Mrhos3 increased the relative expression of citrinin biosynthetic pathway genes including pksCT, mrl1, mrl2, mrl4, mrl6, and mrl7. In addition, deletion of Mrhos3 led to an increase in total pigment content and six classic pigment components. Western blot results revealed that deletion of Mrhos3 could significantly elevate the acetylation level of H3K9, H4K12, H3K18, and total protein. This study provides an important insight into the effects of hos3 gene on the secondary metabolites production in filamentous fungi.

Production of red yeast rice rich in monacolin K by variable temperature solid fermentation of Monascus purpureus

Hypercholesterolemia represents a serious public health problem as it significantly increases the risk of developing cardiovascular diseases. Monacolin K (MK) in red yeast rice is an active compound that can effectively lower plasma cholesterol. To enhance the yield of MK in solid state fermentation of Monascus purpureus HNU01, the effects of different variables were systematically examined in single-factor experiments. The optimal conditions for the production of red yeast rice rich in MK were as follows: initial pH value 5.5, initial moisture content 40% w/w, glucose 50 g L-1, peptone 20 g L-1, MgSO4 0.5 g L-1, KH2PO4 1 g L-1, variable temperature fermentation (30 °C for the first 3 days and then 24 °C for 15 days), total fermentation time of 18 days, and additional water added at day 4 at 10% w/w. Under the above optimized conditions, the MK content of red yeast rice produced by fermentation was 9.5 mg g-1. No citrinin was detected in any of the batches of fermentation products. The results will be useful for the large-scale production of high-quality red yeast rice with health benefits for consumers.

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.

Supplementary effect of whey components on the monascin productivity of Monascus sp

BACKGROUND

Monascus sp. has been used in fermented foods for centuries. It can synthesize yellow, red, and orange pigments as secondary metabolites. Here, we focused on yellow pigment monascin, responsible for anti-inflammation and antidiabetic effects, and investigated whether whey could be a suitable substrate with or without rice powder for monascin production using M. purpureus AHU 9085, M. pilosus NBRC 4520 and M. ruber NBRC 32318.

RESULTS

The growth and monascin production of the three Monascus strains were dependent on three liquid media consisting of whey and/or rice. All strains showed the best growth in a rice and whey mixed medium, in which M. ruber NBRC 32318 exhibited the highest total monascin production. Subsequent investigation of the effects of whey components indicated that a mineral cocktail in whey was particularly effective in stimulating the monascin production efficiency of M. ruber NBRC 32318. However, this recipe exhibited less stimulation, or even inhibition, for M. pilosus NBRC 4520 and M. purpureus AHU 9085, respectively. In terms of total monascin production, rice with whey provided the highest amount due to growth promotion along with relatively high production efficiency.

CONCLUSION

The effect of whey on growth and monascin production was strongly dependent on the Monascus strains. Even a mineral cocktail in whey could regulate monascin productivity in a strain-specific manner. Further studies are needed to elucidate the mechanism behind the diverse responses by the minerals in the production of monascin from Monascus. © 2023 Society of Chemical Industry.

Natural Pigments Production and Their Application in Food, Health and Other Industries

In addition to fulfilling their function of giving color, many natural pigments are known as interesting bioactive compounds with potential health benefits. These compounds have various applications. In recent times, in the food industry, there has been a spread of natural pigment application in many fields, such as pharmacology and toxicology, in the textile and printing industry and in the dairy and fish industry, with almost all major natural pigment classes being used in at least one sector of the food industry. In this scenario, the cost-effective benefits for the industry will be welcome, but they will be obscured by the benefits for people. Obtaining easily usable, non-toxic, eco-sustainable, cheap and biodegradable pigments represents the future in which researchers should invest.

Fungal Pigments: Carotenoids, Riboflavin, and Polyketides with Diverse Applications

Natural pigments and colorants have seen a substantial increase in use over the last few decades due to their eco-friendly and safe properties. Currently, customer preferences for more natural products are driving the substitution of natural pigments for synthetic colorants. Filamentous fungi, particularly ascomycetous fungi (Monascus, Fusarium, Penicillium, and Aspergillus), have been shown to produce secondary metabolites containing a wide variety of pigments, including β-carotene, melanins, azaphilones, quinones, flavins, ankaflavin, monascin, anthraquinone, and naphthoquinone. These pigments produce a variety of colors and tints, including yellow, orange, red, green, purple, brown, and blue. Additionally, these pigments have a broad spectrum of pharmacological activities, including immunomodulatory, anticancer, antioxidant, antibacterial, and antiproliferative activities. This review provides an in-depth overview of fungi gathered from diverse sources and lists several probable fungi capable of producing a variety of color hues. The second section discusses how to classify coloring compounds according to their chemical structure, characteristics, biosynthetic processes, application, and present state. Once again, we investigate the possibility of employing fungal polyketide pigments as food coloring, as well as the toxicity and carcinogenicity of particular pigments. This review explores how advanced technologies such as metabolic engineering and nanotechnology can be employed to overcome obstacles associated with the manufacture of mycotoxin-free, food-grade fungal pigments.

Nanoemulsion containing Yellow Monascus pigment : Fabrication, characterization, storage stability, and lipase hydrolytic activity in vitro digestion

The natural pigment of monascus is favored by human for its special coloring and physiological activity, and its development and application have attracted much attention. In this study, a novel corn oil-based nanoemulsion encapsulated with Yellow Monascus Pigment crude extract (CO-YMPN) was successfully prepared via the phase inversion composition method. The fabrication and stable conditions of the CO-YMPN including Yellow Monascus pigment crude extract (YMPCE) concentration, emulsifier ratio, pH, temperature, ionic strength, monochromatic light and storage time were investigated systemically. The optimized fabrication conditions were the emulsifier ratio (5:3 ratio of Tween 60 to Tween 80) and the YMPCE concentration (20.00% wt%)). Additionally, the DPPH radical scavenging capability of the CO-YMPN (19.47 ± 0.52%) was more excellent than each YMPCE or corn oil. Moreover, the kinetic analysis results based on Michaelis-Menten equation and constant revealed that CO-YMPN could improve lipase hydrolysis capacity. Therefore, the CO-YMPN complex had excellent storage stability and water solubility in the final water system, and the YMPCE showed brilliant stability.

A Zn(II)(2)Cys(6) transcription factor MPsGeI suppresses pigment biosynthesis in Monascus

High-quality natural edible pigments known as monascus pigments (MPs) are widely used in food, medicine, and chemical industries as active functional ingredients. At the transcriptional level, the expression of MPs genes are tightly controlled, limiting their productivity and color value. Hitherto our understanding of the regulation of expression of MPs genes has been rather limited. Here, we describe a pathway-specific Zn(II)(2)Cys(6) transcription factor involved in the MPs biosynthetic cluster named MPsGeI, which encodes a 813-amino-acid protein with six introns. Expression of all MPs biosynthetic genes and accumulation of MPs were remarkably increased in ΔMPsGeI strain, and MPs production was significantly reduced in MPsGeI over-expressing strain. Results clearly demonstrated that MPsGeI negatively regulates MPs accumulation via transcriptional regulation of MPs biosynthetic genes, and plays a central repressive role in MPs' biosynthesis. Transcriptomic analyses revealed that MPsGeI disruptant regulated higher concentrations of precursors flowing to pigment and resulted in accumulation of a large amount of red MPs in hyphae. This work offers an efficient method for increasing MPs's productivity and color value and provides novel insights into the regulatory mechanisms of fungal cellular processes, which will assist to enhance MPs production and application.

Characterization of the Red Biochromes Produced by the Endophytic Fungus Monascus purpureus CPEF02 with Antimicrobial and Antioxidant Activities

Food acceptability and appeal are significantly influenced by colour. Harmful effects associated with synthetic colorants are well established, and research is currently focused on developing natural, synthetic chemical-free substitutes from fungal sources, with broad applications in food, medicine, textiles and agriculture. Additionally, the market’s dearth of natural red colour substitutes requires the creation of novel red pigment alternatives from secure and scalable sources. The goal of the current research was to establish new endophytic marine fungi that are naturally occurring bio-sources of the red pigment. Based on its profuse extracellular red pigment-producing capacity, the fungus CPEF02 was selected and identified as Monascus purpureus CPEF02 via internal transcribed spacer (ITS) sequences and phylogenetic analysis. The chemical moieties of the pigmented extracts were identified by liquid chromatography-high resolution mass spectrometry (LC-HRMS). The optimal culture conditions for maximum pigment production were investigated by surveying various media compositions. The methanolic fungal colourant extract was shown to have substantial antibacterial and antifungal activities against anthropogenic pathogens, Staphylococcus aureus (MTCC 1430), methicillin-resistant Staphylococcus aureus (ATCCBAA811), Salmonella typhimurium (MTCC 3241) and Vibrio cholerae (N16961) at a 100 µg/mL concentration and at a 1 mg/mL concentration for Alternaria solani (ITCC 4632) and Rhizoctonia solani (AG1-IA). This extract also exhibited antioxidant activity against the 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) radical with an IC50 of 14.42 µg/mL and a Trolox equivalent antioxidant capacity of 0.571 µM Trolox/µg of the methanolic colourant extract. The findings suggested that M. purpureus’s pigment could be a source of an industrially useful natural red colourant.

Characterization and metabolomic profiling of two pigment producing fungi from infected fruits of Indian Gooseberry

Two pigment producing fungi, Talaromyces atroroseus and Penicillium choerospondiatis, were isolated and identified from infected fruits of Phyllanthus emblica L. based on amplification and sequencing of internal transcribed spacer region and beta-tubulin gene. This is the first occurrence report of these two fungi from fruits of P. emblica. Culture extract containing metabolites of T. atroroseus and P. choerospondiatis contained phenolics of 26.35 mg and 30.89 mg GAE/g dry extract respectively; whereas no significant amount of flavonoids and tannins were detected. P. choerospondiatis metabolites extract showed higher DPPH and ABTS activity with IC₅₀ values of 21.94 mg/ml and 27.03 mg/ml respectively than T. atroroseus. LC-HRMS analysis of metabolites extract of T. atroroseus revealed presence of trimethyl-isopropyl-butanamide, perlolyrine, N-hexadecanoylpyrrolidine etc. whereas P. choerospondiatis displayed presence of tangeraxanthin, ugaxanthone, daphniphylline, etc. Therefore, fungal metabolites are rich natural sources of diversified compounds that can be utilized in dyeing industries, cosmetics and novel drug development.

-Improved natural food colorant production in the filamentous fungus Monascus ruber using CRISPR-based engineering

Monascus pigments have various food industry applications and are pharmacologically active. Genome sequencing-based clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9) technology has been implemented to increase pigment production in Monascus. To increase pigment production in M. ruber KACC46666, the CRISPR/Cas9 system was used to introduce mutations in two negative regulator genes (MpigI and MpigI'), among other genes involved in the Monascus pigment biosynthesis pathway. Dual single-guide RNAs were constructed to inactivate MpigI and MpigI'. After CRISPR/Cas9 inactivation, yellow, orange, and red pigment expression in the resulting △MpigI16-7 strain (among several Cas9-mediated mutants studied) was 2.5-, 12.4-, and 18.5-fold, respectively, higher than that in the wild-type strain. This study provides valuable information regarding CRISPR-guided metabolic engineering for natural colorant production.

Inhibitory effect of Monascus purpureus pigment extracts against fungi and mechanism of action

The fungus Monascus produces several secondary metabolites of different pigment hues. These pigments have shown various biological activities. In this study, Monascus purpureus pigment extracts were tested (in vitro) against Penicillium expansum MTCC 4900, Rhizopus stolinfer MTCC 10595, and Aspergillus niger MTCC 8652 for antifungal activity. The UV–visible spectrum of M. purpureus fermented rice extracts showed λmax at 395, 425, and 500 nm. This indicated the solubility of yellow, orange, and red pigments in polar-based solvent extraction. The M. purpureus pigment extracts inhibited the radial growth and conidial germination of the test fungi. The fungi treated with pigment extract stained with DiBAC (a vital stain) emitted green fluorescence under a fluorescent microscope. These results indicated that the pigment extracts have affected the membrane potential of the treated fungi. Hence, the fungicidal activity of the pigment extracts is due to the disruption of the cell membrane. The HPLC analysis of the pigment revealed the presence of two major peaks. The UV–visible spectrum corresponding to the HPLC peak at 12-min retention time revealed the presence of orange pigment rubropunctatin. Apparently the rubropunctatin present in the extracts exhibited fungicidal activity. Further studies are warranted to assess the applications of M. purpureus pigments in preventing and treating fungus-related diseases.

Monascus Yellow Pigment Production by Coupled Immobilized-Cell Fermentation and Extractive Fermentation in Nonionic Surfactant Micelle Aqueous Solution

Microbial fermentation with immobilized cells possesses many advantages. However, this fermentation mode is restricted to the production of extracellular products. Our previous study demonstrated that the extractive fermentation of Monascus spp. in nonionic surfactant micelle aqueous solution can export Monascus pigments that are supposed to be mainly intracellular products to extracellular culture broth and, in the meantime, extracellularly enhance the production of yellow pigments at a low pH condition; consequently, this makes the continuous production of yellow pigments with immobilized Monascus cells feasible. In this study, immobilized-cell fermentation and extractive fermentation in Triton X-100 micelle aqueous solution were successfully combined to continuously produce Monascus yellow pigments extracellularly. We examined the effects of cell immobilization and Triton X-100 on cell growth, pigment production, and pigment composition. In the repeated-batch extractive fermentation with immobilized cells, the biomass in Ca-alginate gel beads continued to grow and reached 21.2 g/L after seven batches, and dominant yellow pigments were produced extracellularly and stable for each batch. The mean productivity of the extracellular yellow pigments reached up to 22.31 AU410 nm/day within the first four batches (13 days) and 19.7 AU410 nm/day within the first seven batches (25 days). The results also provide a new strategy for producing such intracellular products continuously and extracellularly.

Overexpression of MrEsa1 accelerated growth, increased ascospores yield, and the polyketide production in Monascus ruber

Esa1 has been proven to be an important histone acetyltransferase involved in the regulation of growth and metabolism. Monascus spp. with nearly 2000 years of edible history in East Asian countries can produce a variety of polyketides. It is unknown whether Esa1 plays a regulatory role in Monascus spp. In this study, we isolated the homology of histone acetyltransferase Esa1 (named MrEsa1) and constructed a mresa1-overexpressed strain. Western blot experiments showed that MrEsa1 hyperacetylated at K4 and K9 of the H3 subunit in Monascus ruber. Overexpression of mresa1 led to the larger colony diameter and increased dry cell mass; meanwhile, the conidia germination rate was significantly accelerated in the mresa1-overexpressed strain before 4 h, and the number of ascospores in the mresa1-overexpressed strain was significantly higher than that in WT. In addition, the Monascus azaphilone pigments (MonAzPs) and citrinin production of the mresa1-overexpressed strain were 1.7 and 2.4 times more than those of WT, respectively. Reverse transcription-quantitative polymerase chain reaction experiment suggested that mrpigB, mrpigH, mrpigJ, and mrpigK, involved in MonAzPs synthesis, and pksCT, mrl3, and mrl7, involved in citrinin synthesis, were upregulated in mresa1-overexpressed strain. This study provides important insights into the effect of MrEsa1 on the developmental process and the production of secondary metabolites in Monascus spp.

Monascin and ankaflavin-Biosynthesis from Monascus purpureus, production methods, pharmacological properties: A review

Monascus purpureus copiously yields beneficial secondary metabolites , including Monascus pigments, which are broadly used as food additives, as a nitrite substitute in meat products, and as a colorant in the food industry. Monascus yellow pigments (monascin and ankaflavin) have shown potential antidiabetic, antibacterial, anti-inflammatory, antidepressant, antibiotic, anticancer, and antiobesity activities. Cosmetic and textile industries are other areas where it has established its potential as a dye. This paper reviews the production methods of Monascus yellow pigments, biosynthesis of Monascus pigments from M. purpureus, factors affecting yellow pigment production during fermentation, and the pharmacological properties of monascin and ankaflavin.

Nitrogen Enriched Solid-State Cultivation for the Overproduction of Azaphilone Red Pigments by Penicillium sclerotiorum SNB-CN111

Azaphilones are microbial specialized metabolites employed as yellow, orange, red or purple pigments. In particular, yellow azaphilones react spontaneously with functionalized nitrogen groups, leading to red azaphilones. In this study, a new two-step solid-state cultivation process to produce specific red azaphilones pigments was implemented, and their chemical diversity was explored based on liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) and a molecular network. This two-step procedure first implies a cellophane membrane allowing accumulating yellow and orange azaphilones from a Penicillium sclerotiorum SNB-CN111 strain, and second involves the incorporation of the desired functionalized nitrogen by shifting the culture medium. The potential of this solid-state cultivation method was finally demonstrated by overproducing an azaphilone with a propargylamine side chain, representing 16% of the metabolic crude extract mass.

The acyl-CoA-binding protein 2 exhibited the highest affinity for palmitoyl-CoA and promoted Monascus pigment production

Purpose

The present study aimed to explore the binding ability of acyl-CoA binding protein 2 to fatty acid acyl-CoA esters and its effect on Monascus pigment production in M. ruber CICC41233.

Methods

The Mracbp2 gene from M. ruber CICC41233 was cloned with a total DNA and cDNA as the templates through the polymerase chain reaction. The cDNA of the Mracbp2 gene fragment was ligated to expression vector pGEX-6P-1 to construct pGEX-MrACBP2, which was expressed in Escherichia coli BL21 to obtain the fusion protein GST-MrACBP2 and then measure the binding ability of fatty acid acyl-CoA esters. Additionally, the DNA of the Mracbp2 gene fragment was ligated to expression vector pNeo0380 to construct pNeo0380-MrACBP2, which was homologously over-expressed in M. ruber CICC41233 to evaluate Monascus pigment production and fatty acid.

Results

The cloned Mracbp2 gene of the DNA and cDNA sequence was 1525 bp and 1329 bp in length, respectively. The microscale thermophoresis binding assay revealed that the purified GST-MrACBP2 had the highest affinity for palmitoyl-CoA (Kd =70.57 nM). Further, the Mracbp2 gene was homologously overexpressed in M. ruber CICC41233, and a positive transformant M. ruber ACBP-E was isolated. In the Monascus pigments fermentation, the expression level of the Mracbp2 gene was increased by 1.74-fold after 2 days and 2.38-fold after 6 days. The palmitic acid content and biomass in M. ruber ACBP2-E were significantly lower than that in M. ruber CICC41233 on 2 days and 6 days. However, compared with M. ruber CICC41233, the yields of total pigment, ethanol-soluble pigment, and water-soluble pigment in M. ruber ACBP2-E increased by 63.61%, 71.61%, and 29.70%, respectively.

Conclusions

The purified fusion protein GST-MrACBP2 exhibited the highest affinity for palmitoyl-CoA. The Mracbp2 gene was overexpressed in M. ruber CICC41233, which resulted in a decrease in palmitic acid and an increase in Monascus pigments. Overall, the effect of MrACBP2 on the synthesis of fatty acid and Monascus pigment was explored. This paper explored the effect of MrACBP2 on the fatty acid synthesis and the synthesis of Monascus pigment. The results indicated the regulation of fatty acid synthesis could affect Monascus pigment synthesis, providing a novel strategy for improving the yield of Monascus pigment.

Utilization of durian seed for Monascus fermentation and its application as a functional ingredient in yogurt

As a widely consumed fermented milk product, yogurt undergoes constant development to increase its functional properties. Monascus purpureus-fermented durian seed, which has been proven to possess antioxidative properties, has the potential to improve yogurt properties. This study aimed to analyze the use of Monascus-fermented durian seed (MFDS) as a functional ingredient in yogurt and its effect on physicochemical properties, lactic acid bacteria (LAB) count, antioxidative properties, and consumer acceptability of set-type yogurt during refrigeration. Changes in physicochemical properties, including color, pH, titratable acidity, syneresis, LAB count, total phenolic content (TPC), and antioxidant activity were evaluated at 7-day intervals during 14 days of refrigerated storage (4 °C). Sensory evaluations were carried out for freshly made samples after 7 days of storage. The results showed that the addition of MFDS to yogurt gave significant effects on some of the parameters measured. Yogurt with added MFDS powder produced a more red color (L = 88.55 ± 1.28, a* = 2.63 ± 0.17, b* = 11.45 ± 1.15, c = 11.75 ± 1.15, H = 77.00 ± 0.64), reached the highest TPC (2.21 ± 0.46 mg/GAE g), antioxidant activity (0.0125 ± 0.0032 mg GAE/g), and syneresis (5.24 ± 0.51%) throughout 14 days of storage. The addition of MFDS only gave a slight difference to pH and titratable acidity, while no significant difference was made for LAB count. For sensory evaluation, the addition of MFDS, particularly the ethanol extract, to yogurt was well-liked by panelists. Citrinin content in MFDS yogurt can be decreased under the limits set. Overall, the addition of MFDS has a high potential of improving yogurt properties, particularly its antioxidative properties.

Chemical characterization and microencapsulation of extracellular fungal pigments

In this work, extracellular colored metabolites obtained from the filamentous fungi Talaromyces australis and Penicillium murcianum, isolated in the Andean-Patagonian native forests of Chile, were studied as prospect compounds to increase the sustainability of cosmetic products. The chemical and antioxidant properties of these natural pigments were characterized and strategies for their microencapsulation were also studied. UHPLC/MS-MS analyses indicated that the predominant metabolites detected in the cultures of P. murcianum were monascin (m/z = 411.15) and monashexenone (m/z = 319.10), while athrorosin H (m/z = 458.20) and damnacanthal (m/z = 281.05) were detected in cultures of T. australis. ORAC tests revealed that P. murcianum's metabolites had the greatest antioxidant properties with values higher than 2000 μmol of trolox equivalents/g. The fungal metabolites were successfully microencapsulated by ionic gelation into structures made of 1.3% sodium alginate, 0.2% chitosan, and 0.07% hyaluronic acid. The microencapsulation process generated structures of 543.57 ± 0.13 µm of mean diameter (d₅₀) with an efficiency of 30% for P. murcianum, and 329.59 ± 0.15 µm of mean diameter (d₅₀) and 40% efficiency, for T. australis. The chemical and biological characterization show the biotechnological potential of these fungal species to obtain pigments with antioxidant activity that could be useful in the cosmetic industry. The encapsulation process enables the production of easy-to-handle dry powder from the fungal metabolites, which could be potentially marketed as a functional cosmetic ingredient. KEY POINTS: • The predominant fungal pigments were of azaphilone and anthraquinoid classes. • The fungal pigments showed high antioxidant activity by ORAC assay. • Fungal pigment microcapsules obtained by ionic gelation were characterized.

Dynamic regulation of Monascus azaphilones biosynthesis by the binary MrPigE-MrPigF oxidoreductase system

Monascus azaphilones (MAs) have been extensively applied as natural food coloring agents. MAs are classified into three categories: yellow MAs (YMAs), orange MAs (OMAs), and red MAs with various biological activities. However, the exact biosynthetic mechanism of OMAs and YMAs are not thoroughly elucidated. Firstly, we identified four DNA-binding residues of transcription factor MrPigB and constructed a multi-site saturation mutagenesis library of MrPigB. Then, comparative metabolite and gene expression of the mutants revealed that two oxidoreductases MrPigE and MrPigF were responsible for the formation of YMAs and OMAs. Finally, the in vitro and in vivo assays demonstrated the opposite roles of MrPigE and MrPigF in conversion of OMAs to YMAs. To our knowledge, this is the first report of a binary oxidoreductase system for dynamic regulation of fungal secondary metabolite biosynthesis. Broadly, our work also demonstrates the transcription factor engineering strategy for elucidating the biosynthetic pathway of secondary metabolite. KEY POINTS: • MrPigE converts orange Monascus azaphilones to yellow Monascus azaphilones • MrPigF oxidizes intermediates to afford orange Monascus azaphilones • MrPigE and MrPigF constitute a binary system in Monascus azaphilones biosynthesis.

Ascomycota as a source of natural colorants

In the last few decades, there has been a great demand for natural colorants. Synthetic colorants are known to be easy to produce, are less expensive, and remain stable when subjected to chemical and physical factors. In addition, only small amounts are required to color any material, and unwanted flavors and aromas are not incorporated into the product. Natural colorants present in food, in addition to providing color, also have biological properties and effects that aid in the prevention and cure of many diseases. The main classes of colorants produced by phylum Ascomycota include polyketides and carotenoids. A promising producer of colorants should be able to assimilate a variety of sources of carbon and nitrogen and also exhibit relative stability. The strain should not be pathogenic, and its product should not be toxic. Production processes should also provide the expected color with a good yield through simple extraction methods. Research that seeks new sources of these compounds should continue to seek products of biotechnological origin in order to be competitive with products of synthetic and plant origin. In this review, we will focus on the recent studies on the main producing species, classes, and metabolic pathways of colorants produced by this phylum, historical background, impact of synthetic colorants on human health and the environment, social demand for natural colorants and also an in-depth approach to bioprocesses (influences on production, optimization of bioprocess, extraction, and identification), and limitations and perspectives for the use of fungal-based dyes.

Study on microbial community of "green-covering" Tuqu and the effect of fortified autochthonous Monascus purpureus on the flavor components of light-aroma-type Baijiu

"Green-covering" Tuqu (TQ), as one of Xiaoqu, is a special fermentative starter (also known as Jiuqu in Chinese) that originated in southern China and is characterized by a layer of green mold covering (Aspergillus clavatus) the surface and (sometimes) with a red heart. It plays a vital role in producing light-aroma-type Baijiu (LATB). However, to date, the microbiota that causes red heart of TQ remain largely unexplored, and it is still unclear how these microbiota influence on the quality of LATB. In this study, two types of TQ, one with a red heart (RH) and another with a non-red heart (NRH), were investigated by high throughput sequencing (HTS) and directional screening of culture-dependent methods. The obtained results revealed the differences in the microbial communities of different TQ and led to the isolation of two species of Monascus. Interestingly, the results of high performance liquid chromatography (HPLC) detection showed that citrinin was not detected, indicating that Monascus isolated from TQ was no safety risk, and the contents of gamma-aminobutyric acid in the fermented grains of RH were higher than that of NRH during the fermentation. Selecting the superior autochthonous Monascus (M1) isolated from the TQ to reinoculate into the TQ-making process, established a stable method for producing the experimental "red heart" Tuqu (ERH), which confirmed that the cause of "red heart" was the growth of Monascus strains. After the lab-scale production test, ERH increased ethyl ester production and reduced higher alcohols production. In addition, Monascus had an inhibitory effect on the growth of Saccharomyces and Aspergillus. This study provides the safe, health-beneficial, and superior fermentation strains and strategies for improving the quality of TQ and LATB.

Construction of gene modification system with highly efficient and markerless for Monascus ruber M7

Monascus spp. are traditional medicinal and edible filamentous fungi in China, and can produce various secondary metabolites, such as Monascus pigments (MPs) and citrinin (CIT). Genetic modification methods, such as gene knock-out, complementation, and overexpression, have been used extensively to investigate the function of related genes in Monascus spp.. However, the resistance selection genes that can have been used for genetic modification in Monascus spp. are limited, and the gene replacement frequency (GRF) is usually <5%. Therefore, we are committed to construct a highly efficient gene editing system without resistance selection marker gene. In this study, using M. ruber M7 as the starting strain, we successfully constructed a so-called markerlessly and highly genetic modification system including the mutants ΔmrpyrGΔmrlig4 and ΔmrpyrGΔmrlig4::mrpyrG, in which we used the endogenous gene mrpyrG from M. ruber M7 instead of the resistance marker gene as the screening marker, and simultaneously deleted mrlig4 related to non-homologous end joining in M. ruber M7. Then, the morphology, the growth rate, the production of MPs and CIT of the mutants were analyzed. And the results show that the mutant strains have normal mycelia, cleistothecia and conidia on PDA+Uridine(U) plate, the biomass of each mutant is also no different from M. ruber M7. However, the U addition also has a certain effect on the orange and red pigments yield of M. ruber M7, which needs our further study. Finally, we applied the system to delete multiple genes from M. ruber M7 separately or continuously without any resistance marker gene, and found that the average GRF of ΔmrpyrGΔmrlig4 was about 18 times of that of M. ruber M7. The markerlessly and highly genetic modification system constructed in current study not only will be used for multi-gene simultaneous modification in Monascus spp., and also lays a foundation for investigating the effects of multi-genes modification on Monascus spp..

A new endophyte Monascus ruber SRZ112 as an efficient production platform of natural pigments using agro-industrial wastes

A number of biopigment applications in various industrial sectors are gaining importance due to the growing consumer interest in their natural origin. Thus, this work was conducted to valorize endophytic fungi as an efficient production platform for natural pigments. A promising strain isolated from leaves of Origanum majorana was identified as Monascus ruber SRZ112 produced several types of pigments. The nature of the pigments, mainly rubropunctamine, monascin, ankaflavin, rubropunctatin, and monascorubrin in the fungal extract was studied by LC/ESI-MS/MS analyses. As a first step towards developing an efficient production of red pigments, the suitability of seven types of agro-industrial waste was evaluated. The highest yield of red pigments was obtained using potato peel moistened with mineral salt broth as a culture medium. To increase yield of red pigments, favourable culture conditions including incubation temperature, incubation period, pH of moistening agent, inoculum concentration, substrate weight and moisture level were evaluated. Additionally, yield of red pigments was intensified after the exposure of M. ruber SRZ112 spores to 1.00 KGy gamma rays. The final yield was improved by a 22.12-fold increase from 23.55 to 3351.87 AU g-1. The anticancer and antioxidant properties of the pigment's extract from the fungal culture were also studied. The obtained data indicated activity of the extract against human breast cancer cell lines with no significant cytotoxicity against normal cell lines. The extract also showed a free radical scavenging potential. This is the first report, to our knowledge, on the isolation of the endophytic M. ruber SRZ112 strain with the successful production of natural pigments under solid-state fermentation using potato peel as a substrate.

Metabolomics Analysis Coupled with Weighted Gene Co-Expression Network Analysis Unravels the Associations of Tricarboxylic Acid Cycle-Intermediates with Edible Pigments Produced by Monascus purpureus (Hong Qu)

Monascus azaphilones pigments (MonAzPs) produced by microbial fermentation are widely used as food chemicals for coloring and supplying beneficial biological attributes. In this study, a fermentation perturbation strategy was implemented by separately adding different amino acids, and detecting the intracellular metabolome via UHPLC-Q-Orbitrap HRMS. With the aid of weighted gene co-expression network analysis, two metabolic intermediates, fumarate and malate, involved in the tricarboxylic acid cycle, were identified as the hub metabolites. Moreover, exogenous addition of fumarate or malate significantly promoted red pigment production, and reduced orange/yellow pigment production. The importance of the tricarboxylic acid cycle was further emphasized by detecting intracellular levels of ATP, NAD(P)H, and expression of oxidoreductase-coding genes located in the MonAzPs synthetic gene cluster, suggesting a considerable effect of the energy supply on MonAzPs synthesis. Collectively, metabolomics is a powerful approach to position the crucial metabolic regulatory factors, and facilitate the development of engineering strategies for targeted regulation, lower trial-and-error cost, and advance safe and controllable processes for fermented food chemistry industries.

Diverse Effects of Amino Acids on Monascus Pigments Biosynthesis in Monascus purpureus

Amino acids could act as nitrogen sources, amido group donors, or bioactive molecules in fungi fermentation, and consequently, play important roles in Monascus pigments (MPs) biosynthesis. But the understanding of the effects of various amino acids on MPs biosynthesis is still incomprehensive. In this work, 20 free amino acids were added to the fermentation medium to evaluate their effects on MPs biosynthesis in Monascus purpureus RP2. Six amino acids, namely, histidine (HIS), lysine (LYS), tyrosine (TYR), phenylalanine (PHE), methionine (MET), and cysteine (CYS), were selected as the valuable ones as they exerted significant effects on the production yield and even on the biosynthesis metabolic curves of MPs. Moreover, the dose-dependent and synergistic effects of valuable amino acids on MPs biosynthesis were observed by tests of serial concentrations and different combinations. In addition, it revealed that HIS and MET were the prominent amino acids with dominant and universal influences on MPs biosynthesis. The analog compounds of HIS (amitrole) and MET [calcium 2-hydroxy-4-(methylthio)] were added to the fermentation medium, and the results further confirmed the extraordinary effects of HIS and MET and their analogs on MPs biosynthesis. Furthermore, the gene transcription profile indicated that a differential expression pattern was observed in the polyketide synthase (PKS) cluster responsible for MPs biosynthesis in response to HIS and MET, revealing that they could oppositely regulate MPs biosynthesis in different ways. These findings would benefit the understanding of MPs biosynthesis regulation mechanism in M. purpureus and contribute to the industrial production of MPs by fermentation.

Increased Water-Soluble Yellow Monascus Pigment Productivity via Dual Mutagenesis and Submerged Repeated-Batch Fermentation of Monascus purpureus

Monascus pigments (MPs) have been used in the food industry for more than 2,000 years and are known for their safety, bold coloring, and physiological activity. MPs are mainly yellow (YMPs), orange (OMPs), and red (RMPs). In this study, a mutant strain Monascus purpureus H14 with high production of water-soluble YMPs (WSYMPs, λ_max at 370 nm) was generated instead of primary YMPs (λ_max at 420 nm), OMPs (λ_max at 470 nm), and RMPs (λ_max at 510 nm) produced by the parent strain M. purpureus LQ-6 through dual mutagenesis of atmospheric and room-temperature plasma and heavy ion beam irradiation (HIBI), producing 22.68 U/ml extracellular YMPs and 10.67 U/ml intracellular YMPs. WSYMP production was increased by 289.51% in optimal conditions after response surface methodology was applied in submerged fermentation. Application of combined immobilized fermentation and extractive fermentation improved productivity to 16.89 U/ml/day, 6.70 times greater than with conservative submerged fermentation. The produced WSYMPs exhibited good tone stability to environmental factors, but their pigment values were unstable to pH, light, and high concentrations of Ca²⁺, Zn²⁺, Fe²⁺, Cu²⁺, and Mg²⁺. Furtherly, the produced exYMPs were identified as two yellow monascus pigment components (monascusone B and C₂₁H₂₇NO₇S) by UHPLC-ESI-MS. This strategy may be extended to industrial production of premium WSYMPs using Monascus.

Red yeast rice dietary intervention reduces oxidative stress-related inflammation and improves intestinal microbiota

Inflammation and oxidative stress play key roles in the aging process, while red yeast rice (RYR), a traditional Chinese fermented food, has anti-oxidant and anti-inflammatory effects. To understand the anti-aging function of RYR in vivo, this study established a D-galactose-induced aging mouse model to verify the positive effects of RYR dietary intervention on aging and explore the related underlying mechanism. Eight weeks of RYR dietary intervention was shown to have a significant inhibitory effect on cognitive decline and hippocampal damage. The molecular mechanistic studies showed that the anti-aging effects of RYR were achieved by (i) improving the oxidative stress-related damage (increasing SOD, CAT, and GSH, and reducing MDA), (ii) regulating the NF-κB inflammation pathway induced by oxidative stress (decreasing the pro-inflammatory cytokines IL-6, TNF-α, IFN-γ, iNOs, and IL-1β, increasing the anti-inflammatory cytokine IL-10, and decreasing the expression of the NF-κB protein), (iii) slowing down apoptosis caused by oxidative stress (reducing the expression of P21 and P53), (iv) restoring the abundance of Lactobacillus, Lachnospiraceae and Rikenellaceae downregulated by D-galactose, and (v) reducing the abundance of Akkermansia and Helicobacter enriched by D-galactose. Mass spectrometry revealed orange pigments (rubropunctatin and monascorubrin) as the main antioxidant components in RYR, which might play key roles in aging inhibition. This study provides theoretical support for the wide application of orange pigments as an antioxidant dietary supplement.

Methionine and S-Adenosylmethionine Regulate Monascus Pigments Biosynthesis in Monascus purpureus

Amino acid metabolism could exert regulatory effects on Monascus pigments (MPs) biosynthesis. In this work, MPs biosynthesis regulated by methionine and S-adenosylmethionine (SAM) was investigated in Monascus purpureus RP2. The results indicated that the addition of methionine in fermentation significantly reduced MPs production by 60–70%, and it induced a higher expression of SAM synthetase Mon2A2272 and consequently led to SAM accumulation. However, the addition of SAM in fermentation promoted MPs production by a maximum of 35%, while over-expression of the gene Mon2A2272 led to a decrease in MPs yield, suggesting that SAM synthetase and SAM were likely to play different regulatory roles in MPs biosynthesis. Furthermore, the gene transcription profile indicated that SAM synthetase expression led to a higher expression of the transcriptional regulatory protein of the MPs biosynthesis gene cluster, while the addition of SAM gave rise to a higher expression of MPs biosynthesis activator and the global regulator LaeA, which probably accounted for changes in MPs production and the mycelium colony morphology of M. purpureus RP2 triggered by methionine and SAM. This work proposed a possible regulation mechanism of MPs biosynthesis by SAM metabolism from methionine. The findings provided a new perspective for a deep understanding of MPs biosynthesis regulation in M. purpureus.

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.

Insight into the Progress on Natural Dyes: Sources, Structural Features, Health Effects, Challenges, and Potential

(1) Background: Dyes play an important role in food, medicine, textile, and other industries, which make human life more colorful. With the increasing demand for food safety, the development of natural dyes becomes more and more attractive. (2) Methods: The literature was searched using the electronic databases PubMed, Web of Science, and SciFinder and this scoping review was carried out following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). (3) Results: 248 articles were included in this review. This review summarizes the research progress on natural dyes in the last ten years. According to structural features, natural dyes mainly include carotenoids, polyphenols, porphyrins, and alkaloids, and some of the newest dyes are summarized. Some pharmacological activities of carotenoids, anthocyanin, curcumin, and betalains in the last 10 years are summarized, and the biological effects of dyes regarding illumination conditions. The disadvantages of natural dyes, including sources, cost, stability, and poor bioavailability, limit their application. Here, some feasible strategies (potential resources, biotechnology, new extraction and separation strategies, strategies for improving stability) are described, which will contribute to the development and utilization of natural dyes. (4) Conclusion: Natural dyes show health benefits and potential in food additives. However, it is necessary for natural dyes to pass toxicity tests and quality tests and receive many regulatory approvals before their final entry into the market as food colorants or as drugs.

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.

Utilization of low-cost agricultural by-product rice husk for Monascus pigments production via submerged batch-fermentation

BACKGROUND

Monascus pigments (MPs) produced by the genus Monascus, have been utilized for more than 2000 years in the food industry. In the present study, by submerged batch-fermentation (SBF), we were able to obtain a mutant strain with a high tolerance of inhibitory compounds generated from rice husk hydrolysate, allowing the production of MPs.

RESULTS

The mutant strain, M. Purpureus M523 with high rice husk hydrolysate tolerance was obtained using the atmospheric and room temperature plasma (ARTP) screening system, producing 39.48 U mL^-1 extracellular total MPs (yellow and orange MPs), using non-detoxified rice husk diluted sulfuric acid hydrolysate (RHSAH) as the carbon source in SBF. Extracellular MPs (exMPs) production was enhanced to 72.1 and 80.7 U mL^-1 in supplemented SBF (SSBF) and immobilized fermentation (IF) using non-detoxified RHSAH, with productivities of 0.16 and 0.37 U mL^-1  h^-1 , respectively. In addition, our findings revealed that despite having a high RHSAH tolerance, the mutant strain was unable to degrade phenolic compounds. Furthermore, we discovered that inhibitory compounds, including furfural (Fur) and 5'-hydroxymethyl furfural (5'-HMF), not only inhibit MP biosynthesis, but also regulate the conversion of pigment components.

CONCLUSION

The low-cost agricultural by-product, rice husk, can serve as an efficient substitute for MP production with high productivity via IF by Monascus spp. © 2021 Society of Chemical Industry.