Monascus orange and red pigments production by Monascus purpureus ATCC16436 through co-solid state fermentation of corn cob and glycerol: An eco-friendly environmental low cost approach

Biotechnological potential of Monascus: Biological aspects, metabolites of interest, and opportunities for new products

The need to develop more sustainable products and processes qualifies microbial platforms for obtaining products as a highlighted interesting solution. In this context, filamentous fungi that produce biopigments have been emphasized, especially in the development of research, products and industrial applications. Among the different species, the genus Monascus stands out, either because of its popular use in traditional communities or even because of its versatile growth capacity. Indeed, it is able to metabolize different substrates, including agro-industrial wastes and by-products, as well as allowing different cultivation approaches, such as solid-state and submerged fermentation, for the production of biopigments. Its best-known products include biopigments (yellow, orange and red) and diverse secondary metabolites which have proven biological properties and have great potential in food, pharmaceutical and cosmetic formulations. This review presents the biotechnological, biochemical, and innovation potential of fungi from the genus Monascus, encompassing their historical importance, recent studies on cultivation and production of biopigments, beside the potential of this emerging platform for producing microbial biopigments.

RNA-Seq Insight into the Impact and Mechanisms of Methyl Donor and Glycine Betaine Osmoprotectant on Polyketide Secondary Metabolism in Monascus purpureus M1

Glycine betaine (GB) serves as both a methyl donor and osmoprotectant in microorganisms, facilitating growth and enhancing metabolic product yields. While the polyketide metabolites from Monascus purpureus, such as Monascus pigments (MPs) and monacolin K (MK), have been extensively studied, the effects of GB on their production and the underlying molecular mechanisms remain insufficiently explored. In this study, various concentrations of GB were added to Monascus purpureus M1 cultures, followed by RNA sequencing, RT-qPCR, differential gene expression analysis, and functional enrichment to investigate the regulatory impact of GB on polyketide metabolism. Protein-protein interaction network analysis identified key upregulated genes, including RPS15, RPS14, RPS5, NDK1, EGD2, and ATP9, particularly during the later growth phases. GB significantly upregulated genes involved in stress response, secondary metabolism, and polyketide biosynthesis. Scanning electron microscopy, HPLC, and UV-Vis spectrophotometry further confirmed that GB promoted both strain growth and polyketide production, with red pigment and MK production increasing by 120.08% and 93.4%, respectively. These results indicate that GB enhances growth and polyketide metabolism in Monascus purpureus by functioning as both a methyl donor and osmoprotectant, offering new insights into optimizing microbial polyketide production and revealing gene regulatory mechanisms by GB in Monascus purpureus.

Lignocellulosic materials valorization in second generation biorefineries: an opportunity to produce fungal biopigments

Second generation biorefineries play an important role in the production of renewable energy and fuels, utilizing forest and agro-industrial residues and by-products as raw materials. The integration of novel bioproducts, such as: xylitol, β-carotene, xylooligosaccharides, and biopigments into the biorefinery's portfolio can offer economic benefits in the valorization of lignocellulosic materials, particularly cellulosic and hemicellulosic fractions. Fungal biopigments, known for their additional antioxidant and antimicrobial properties, are appealing to consumers and can have applications in various industrial sectors, including food and pharmaceuticals. The use of lignocellulosic materials as carbon and nutrient sources for the growth medium helps to reduce production costs, increasing the competitiveness of fungal biopigments in the market. In addition, the implementation of biopigment production in biorefineries allows the utilization of underutilized fractions, such as hemicellulose, for value-added bioproducts. This study deals with the potential of fungal biopigments production in second generation biorefineries in order to diversify the produced biomolecules together with energy generation. A comprehensive and critical review of the recent literature on this topic has been conducted, covering the major possible raw materials, general aspects of second generation biorefineries, the fungal biopigments and their potential for incorporation into biorefineries.

Monascus red pigment influence on hydroxyapatite nanoparticles-mediated renal toxicity in rats

Hydroxyapatite nanoparticles (HANPs) have been applied in several biomedical fields. However, its interaction with biological systems is less exploited. This study aimed to characterize HANPs, examine their influence on kidneys, and explore the potential protective effects of naturally extracted red pigment (RP) from Monascus purpureus against HANPs-induced renal toxicity. To this aim, forty eight adult male rats were randomly divided into 8 equal groups: a control group receiving 4% dimethyl sulfoxide (the solvent for HANPs), three groups receiving extracted RP at different doses of 10, 20, and 40 mg/kg, a group receiving HANPs at a dose of 88.3 mg/kg, and three more groups receiving a double treatment of HANPs associated with RP. The respective treatment was given daily by oral gavage to animals for 50 days which is the duration of the whole experiment. The renal toxicity caused by HANPs was manifested by aberrations in kidney function parameters, intensification of oxidative stress markers, and a decrease in the activity of antioxidant enzymes. Moreover, an increase in inflammatory (TNF-α and TGF-β) and apoptotic (caspace-3) markers, an elevation in gene-based kidney injuries markers (Kim-1 and lipocalin-2), and pathological tissue changes were determined. Meanwhile, co-treatment with different doses of biopigment and HANPs have reduced oxidative stress via their potent antioxidant effect. This was confirmed by pronounced improvement in the measured parameters along with the histological structural enhancement in a dose dependent manner compared to controls. To sum up, RP from M. purpureus has potential protective benefits in mitigating the adverse effects of HANPs.

Antimicrobial activity of Monascus purpureus-derived red pigments against Salmonella typhimurium, Escherichia coli, and Enterococcus faecalis

The rise of antimicrobial-resistant microorganisms (AMR) poses a significant global challenge to human health and economic stability. In response, various scientific communities are seeking safe alternatives to antibiotics. This study comprehensively investigates the antibacterial effects of red dye derived from Monascus purpureus against three bacterial pathogens: Salmonella typhimurium ATCC14028, Escherichia coli ATCC8739, and Enterococcus faecalis ATCC25923. The dye was extracted from the Monascus purpureus ATCC16436 strain, using 1 mg of red dye in 1 ml of DMSO to achieve a concentration of 1000 µg/ml. The chemical profile of the red dye extract was analyzed using GC-MS analysis, confirming the presence of several bioactive antimicrobial compounds, including aspidospermidin-17-ol, 1-acetyl-16-methoxy, octanoic acid, and hexadecanoic acid methyl ester. The extract was tested against the bacterial strains at varying concentrations to determine the minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The results demonstrated significant antibacterial activity, with the highest MIC and MBC values of 6.25/12.5 µg/ml against S. typhimurium. The antibacterial activity of the red dye was compared to five conventional antibiotics using the disc diffusion method, revealing superior effectiveness, particularly against S. typhimurium, with an inhibition zone measuring 20 ± 0.22 mm. Scanning electron microscopy was employed to explore the mechanism of action of the red dye extract, highlighting its impact on bacterial plasma membrane permeability and its interference with cellular energy production. These findings suggest that the Monascus purpureus-derived red dye extract represents a promising natural alternative to conventional antibiotics, demonstrating potent antibacterial activity and potential as a novel therapeutic agent in combating antimicrobial resistance.

Antibacterial Potential of Honeybee Venom and Monascus purpureus Extracellular Metabolites Against Multidrug-Resistant Pathogenic Bacteria

Antimicrobial resistance (AMR) poses a critical global health threat, driving the search for alternative treatments to conventional antibiotics. In this study, the antibacterial properties of honeybee venom (BV) and fungal Monascus purpureus red dye (RD) were evaluated against three multidrug-resistant bacterial pathogens. Extracts of BV and RD exhibited dose-dependent antibacterial activity against the three tested bacteria, with their strongest effectiveness against S. aureus (minimum inhibitory concentrations [MIC] = 3.18 and 6.315 μg·mL-1, respectively). Although the three bacterial strains were resistant to the antibiotic ampicillin-sulbactam (10/10 µg), both extracts exhibited superior antibacterial activity against the three bacterial strains compared to five standard antibiotics, especially RD extract, which produced the largest inhibition zone (20 ± 0.20 mm) against S. aureus. The larger inhibition zones against S. aureus suggest its high sensitivity, whereas E. coli and E. faecalis exhibited smaller inhibition zones, indicating less sensitivity to BV and RD extracts. Differences in the inhibition zones suggest the variations in antimicrobial activity between the two extracts and their strain-specific effectiveness. Scanning electron microscopy (SEM) revealed that BV and RD extracts disrupted the bacterial plasma membrane, suggesting that the bioactive compounds penetrate the bacterial cell wall and alter its integrity. Furthermore, GC-MS-based analysis revealed that the chemical composition of BV and RD extracts exhibited highly diverse structures, including complex polycyclic systems, porphyrins, steroids, and esters. For instance, 42 metabolites were identified in the BV extract, which mainly were organic and metal-organic compounds; however, only 23 molecules were identified in RD extract, which mainly were fatty acids and their derivatives. The diversity in the chemical compositions of both extracts highlights their potential applications in pharmaceuticals, materials, and biochemistry fields. Collectively, these findings indicate that honeybee venom and the red dye from M. purpureus have promising antibacterial properties and warrant further investigation as potential alternatives to conventional antibiotics. Further multi-ligand docking-based virtual screening studies are required to identify the most promising detected metabolite(s) within both BV and RD extracts.

Synthesis, characterization and application of microbial pigments in foods as natural colors

Colorants have played a crucial role in various applications, particularly in food processing, with natural sources such as mineral ores, plants, insects, and animals being commonly used. However, the nineteenth century saw the development of synthetic dyes, which replaced these natural colorants. In recent years, there has been a growing demand for natural products, driving an increased interest in natural colorants. Microbial pigments have emerged as promising sources of natural pigments due to their numerous health benefits. They can be produced in large quantities rapidly and from more affordable substrates, making them economically attractive. This review focuses on the current advancements in the low-cost synthesis of microbial pigments, exploring their biological activities and commercial applications. Microbial pigments offer a sustainable and economically viable alternative to natural and synthetic colorants, meeting the growing demand for natural products. These pigments are relatively nontoxic and exhibit significant health benefits, making them suitable for a wide range of applications. As interest in natural products continues to rise, microbial pigments hold great potential in shaping the future of colorant production across various sectors.

Modified zero-valent iron nanoparticles enhanced remediation of PCBs-contaminated soil

The high toxicity and persistence of polychlorinated biphenyls (PCBs) in the environment require effective remediation of PCBs-contaminated soil. This study used polylactic acid (PLA) and polyethylene glycol 4000 (PEG-4000) to modify zero-valent iron nanoparticles (nZVI) and conducted characterization analysis. It was found that when the addition amount of PLA was 2 %, the dispersion of modified nZVI was better. The initial pH and water to soil ratio were subjected to single factor experiments and fitted using RSM response surface methodology. The optimal reaction conditions were obtained as follows: the addition amount was 84 g·kg-1, the initial pH was 5.41, and the optimal removal rate was 74 % when the ratio of water to soil was 1.8:1. PLA and PEG-4000 were biodegradable substances that played crucial roles in enhancing the effectiveness of nZVI for PCBs-contaminated soil. By encapsulating nZVI with PLA, we significantly reduced its oxidation when exposed to air. Additionally, the inclusion of PEG-4000 helped prevent the particles from clumping together. The synergistic effect of them increased the effective reaction of nZVI and PCBs and ultimately leading to more efficient remediation. This study offered a new pathway for the efficient green remediation of PCBs-contaminated soil.

Synthetic biology for Monascus: From strain breeding to industrial production

Traditional Chinese food therapies often motivate the development of modern medicines, and learning from them will bring bright prospects. Monascus, a conventional Chinese fungus with centuries of use in the food industry, produces various metabolites, including natural pigments, lipid-lowering substances, and other bioactive ingredients. Recent Monascus studies focused on the metabolite biosynthesis mechanisms, strain modifications, and fermentation process optimizations, significantly advancing Monascus development on a lab scale. However, the advanced manufacture for Monascus is lacking, restricting its scale production. Here, the synthetic biology techniques and their challenges for engineering filamentous fungi were summarized, especially for Monascus. With further in-depth discussions of automatic solid-state fermentation manufacturing and prospects for combining synthetic biology and process intensification, the industrial scale production of Monascus will succeed with the help of Monascus improvement and intelligent fermentation control, promoting Monascus applications in food, cosmetic, agriculture, medicine, and environmental protection industries.

Disruption of UDP-galactopyranose mutase expression: A novel strategy for regulation of galactomannan biosynthesis and monascus pigments secretion in Monascus purpureus M9

The impact of the cell wall structure of Monascus purpureus M9 on the secretion of extracellular monascus pigments (exMPs) was investigated. To modify the cell wall structure, UDP-galactopyranose mutase (GlfA) was knocked out using Agrobacterium-mediated transformation method, leading to a significant reduction in the Galf-based polysaccharide within the cell wall. Changes in mycelium morphology, sporogenesis, and the expression of relevant genes in M9 were also observed following the mutation. Regarding MPs secretion, a notable increase was observed in six types of exMPs (R1, R2, Y1, Y2, O1 and O2). Specifically, these exMPs exhibited enhancement of 1.33, 1.59, 0.8, 2.45, 2.89 and 4.03 times, respectively, compared to the wild-type strain. These findings suggest that the alteration of the cell wall structure could selectively influence the secretion of MPs in M9. The underlying mechanisms were also discussed. This research contributes new insights into the regulation of the synthesis and secretion of MPs in Monascus spp..

The fermentation optimization for alkaline protease production by Bacillus subtilis BS-QR-052

Introduction

Proteases exhibit a wide range of applications, and among them, alkaline proteases have become a prominent area of research due to their stability in highly alkaline environments. To optimize the production yield and activity of alkaline proteases, researchers are continuously exploring different fermentation conditions and culture medium components.

Methods

In this paper, the fermentation conditions of the alkaline protease (EC 3.4.21.14) production by Bacillus subtilis BS-QR-052 were optimized, and the effect of different nutrition and fermentation conditions was investigated. Based on the single-variable experiments, the Plackett-Burman design was used to explore the significant factors, and then the optimized fermentation conditions, as well as the interaction between these factors, were evaluated by response surface methodology through the Box-Behnken design.

Results and discussion

The results showed that 1.03% corn syrup powder, 0.05% MgSO4, 8.02% inoculation volume, 1:1.22 vvm airflow rate, as well as 0.5% corn starch, 0.05% MnSO4, 180 rpm agitation speed, 36°C fermentation temperature, 8.0 initial pH and 96 h incubation time were predicted to be the optimal fermentation conditions. The alkaline protease enzyme activity was estimated to be approximately 1787.91 U/mL, whereas subsequent experimental validation confirmed it reached 1780.03 U/mL, while that of 500 L scale-up fermentation reached 1798.33 U/mL. This study optimized the fermentation conditions for alkaline protease production by B. subtilis through systematic experimental design and data analysis, and the activity of the alkaline protease increased to 300.72% of its original level. The established model for predicting alkaline protease activity was validated, achieving significantly higher levels of enzymatic activity. The findings provide valuable references for further enhancing the yield and activity of alkaline protease, thereby holding substantial practical significance and economic benefits for industrial applications.

Multiplex metabolic pathway engineering of Monascus pilosus enhances lovastatin production

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

A comparative study using response surface methodology and artificial neural network towards optimized production of melanin by Aureobasidium pullulans AKW

The effect of three independent variables (i.e., tyrosine, sucrose, and incubation time) on melanin production by Aureobasidium pullulans AKW was unraveled by two distinctive approaches: response surface methodology (i.e. Box Behnken design (BBD)) and artificial neural network (ANN) in this study for the first time ever using a simple medium. Regarding BBD, sucrose and incubation intervals did impose a significant influence on the output (melanin levels), however, tyrosine did not. The validation process exhibited a high consistency of BBD and ANN paradigms with the experimental melanin production. Concerning ANN, the predicted values of melanin were highly comparable to the experimental values, with minor errors competing with BBD. Highly comparable experimental values of melanin were achieved upon using BBD (9.295 ± 0.556 g/L) and ANN (10.192 ± 0.782 g/L). ANN accurately predicted melanin production and showed more improvement in melanin production by about 9.7% higher than BBD. The purified melanin structure was verified by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction pattern (XRD), and thermogravimetric analysis (TGA). The results verified the hierarchical architecture of the particles as small compasses by SEM analysis, inter-layer spacing in the XRD analysis, maximal atomic % for carbon, and oxygen atoms in the EDX analysis, and the great thermal stability in the TGA analysis of the purified melanin. Interestingly, the current novel endophytic strain was tyrosine-independent, and the uniquely applied ANN paradigm was more efficient in modeling the melanin production with appreciate amount on a simple medium in a relatively short time (168 h), suggesting additional optimization studies for further maximization of melanin production.

Valorization of biowastes as fermentative substrate for production of Exiguobacterium sp. GM010 pigment and toxicity effect in rats

Bioconversion of biowastes chicken feather (CF), prawn carapace (PC), fish scale (FS), and corncob (CC) were used for Exiguobacterium sp. GM010 pigment production to reduce environmental pollution. Maximum pigment was produced in 4 % PC hydrolysate medium at pH 8 and 30 °C (0.831 Absorption Unit-AUmL^-1) compared to other hydrolysate. Biomass (1061.19 ± 26.14 mg/100 mL) and pigment yield (34.26 ± 0.62 mg/100 mL) were higher in PC medium. In CF + PC hydrolysate combination, biomass and pigment yield was 890.58 ± 11.5 mg/100 mL and 13.94 ± 0.17 mg/100 mL, respectively. Carbon and nitrogen ratio in the medium influenced pigment production. The UV-visible spectrum showed absorption peak at 357, 466, and 491 nm. Further hue angle (77-72) and chroma values (8.68-11.38) distributed over yellowish-orange region of CIELAB spectrum indicated carotenoid like characteristics. Wistar rats fed with pigment (2000 mg/kg bw) did not show sign of toxicity in haematological, biochemical and histopathological analysis. Therefore, pigment produced by recycling the biowastes promotes sustainable bioprocess and circular bioeconomy.

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.

Bacteria as biofactory of pigments: Evolution beyond therapeutics and biotechnological advancements

Bacterial pigments are the wonder molecules of nature that have attracted the attention of industries in recent years. To date, various synthetic pigments have been in use in food, cosmetics, and textile industries that have not only shown a notoriously toxic nature but also posed threat to the ecosystem. Moreover, nutraceuticals, fisheries, and animal husbandry were highly dependent on plant sources for products that aid in disease prevention and improve stock health. In this context, the use of bacterial pigments as new-generation colorants, food fortifiers, and supplements can hold great prospects as low-cost, healthy, and eco-friendly alternatives. The majority of studies on these compounds were restricted to antimicrobial, antioxidant, and anticancer potentials to date. Each of these can be highly beneficial for the development of new-generation drugs, but their other potential niche in various industries that pose health and environmental risks needs to be explored. Recent advances in novel strategies of metabolic engineering, advancements in optimization tools for the fermentation process, and the design of appropriate delivery systems will greatly expand the market of bacterial pigments in industries. This review summarizes the current technologies for enhancing production, recovery, stability, and appreciable use of bacterial pigments in industries apart from therapeutics with proper financial aspects. The toxicity perspectives have been focused to emphasize that these wonder molecules are the need of the hour and their future prospects have been highlighted. Extensive literature has been studied to include the challenges of bacterial pigments from environmental and health risk perspectives.

Solid-state fermentation of Saba banana peel for pigment production by Monascus purpureus

Eco-friendly natural pigment demand has ever-increasing popularity due to health and environmental concerns. In this context, the aim of this study was to evaluate the feasibility use of Saba banana peel as low-cost fermentable substrate for the production of pigments, xylanase and cellulase enzymes by Monascus purpureus. Among the strains tested, M. purpureus TISTR 3385 produced pigments better and had higher enzyme activities. Under the optimal pigment-producing conditions at the initial moisture content of 40% and initial pH of 6.0, the pigments comprising yellow, orange, and red produced by the fungi were achieved in the range of 0.40-0.93 UA/g/day. The maximum xylanase and cellulase activities of 8.92 ± 0.46 U/g and 4.72 ± 0.04 U/g were also obtained, respectively. More importantly, solid-state fermentation of non-sterile peel could be achieved without sacrificing the production of the pigments and both enzymes. These indicated the potential use of the peel as fermentable feedstock for pigment production by the fungi and an environmental-friendly approach for sustainable waste management and industrial pigment and enzyme application.

-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.

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

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

Natural Substrates and Culture Conditions to Produce Pigments from Potential Microbes in Submerged Fermentation

Pigments from bacteria, fungi, yeast, cyanobacteria, and microalgae have been gaining more demand in the food, leather, and textile industries due to their natural origin and effective bioactive functions. Mass production of microbial pigments using inexpensive and ecofriendly agro-industrial residues is gaining more demand in the current research due to their low cost, natural origin, waste utilization, and high pigment stimulating characteristics. A wide range of natural substrates has been employed in submerged fermentation as carbon and nitrogen sources to enhance the pigment production from these microorganisms to obtain the required quantity of pigments. Submerged fermentation is proven to yield more pigment when added with agro-waste residues. Hence, in this review, aspects of potential pigmented microbes such as diversity, natural substrates that stimulate more pigment production from bacteria, fungi, yeast, and a few microalgae under submerged culture conditions, pigment identification, and ecological functions are detailed for the benefit of industrial personnel, researchers, and other entrepreneurs to explore pigmented microbes for multifaceted applications. In addition, some important aspects of microbial pigments are covered herein to disseminate the knowledge.

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.

Comparative transcriptomics discloses the regulatory impact of carbon/nitrogen fermentation on the biosynthesis of Monascus kaoliang pigments

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The synthesis of Monascus pigments (MPs) depends on many fermentation conditions.

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Carbon and nitrogen had important effect on the biosynthesis of MPs.

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Comparative transcriptomic provided a comprehensive interpretation of the links between primary and secondary metabolisms in MPs.

Carbon and nitrogen play a fundamental role in the production of Monascus pigments. However, their effects on pigment biosynthesis remain undetermined. In this study, we found that Monascus kaoliang produces pigments via liquid fermentation using glycerol and peptone as suitable carbon and nitrogen sources, respectively. Comparative transcriptomic profiling was performed using RNA sequencing. It indicated that the differentially expressed genes (DEGs) of carbon were enriched using amino acids and carbohydrates via the transport and metabolism pathways, respectively. DEGs of nitrogen were enriched only using general functional prediction pathways. These data provide a comprehensive interpretation of the linkage between primary and secondary metabolisms in M. kaoliang. Moreover, they provide insights into the effects of various substances involved in secondary metabolism.

Lignocellulosic substrates as starting materials for the production of bioactive biopigments

The search for sustainable processes is constantly increasing in the last years, so reusing, recycling and adding value to residues and by-products from agroindustry is a consolidated area of research. Particularly in the field of fermentation technology, the lignocellulosic substrates have been used to produce a diversity of chemicals, fuels and food additives. These residues or by-products are rich sources of carbon, which may be used to yield fermentescible sugars upon hydrolysis, but are usually inaccessible to enzyme and microbial attack. Therefore, pre-treatments (e.g. hydrolysis, steam explosion, biological pretreatment or others) are required prior to microbial action. Biopigments are added-value compounds that can be produced biotechnologically, including fermentation processes employing lignocellulosic substrates. These molecules are important not only for their coloring properties, but also for their biological activities. Therefore, this paper discusses the most recent and relevant processes for biopigment production using lignocellulosic substrates (solid-state fermentation) or their hydrolysates.

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.

Insights on sustainable approaches for production and applications of value added products

The increasing demand for the development of sustainable strategies to utilize and process agro-industrial residues paves new paths for exploring innovative approaches in this area. Biotechnology based microbial transformations provide efficient, low cost and sustainable approaches for the production of value added products. The use of organic rich residues opens new avenues for the production of enzymes, pigments, biofuels, bioactive compounds, biopolymers etc. with vast industrial and therapeutic applications. Innovative technologies like strain improvement, enzyme immobilization, genome editing, morphological engineering, ultrasound/supercritical fluid/pulse electric field extraction, etc. can be employed. These will be helpful in achieving significant improvement in qualitative and quantitative parameters of the finished products. The global trend for the valorisation of biowaste has boosted the commercialization of these products which has transformed the markets by providing new investment opportunities. The upstream processing of raw materials using microbes poses a limitation in terms of product development and recovery which can be overcome by modifying the bioreactor design, physiological parameters or employing alternate technologies which will be discussed in this review. The other problems related to the processes include product stability, industrial applicability and cost competitiveness which needs to be addressed. This review comprehensively discusses the recent progress, avenues and challenges in the approaches aimed at valorisation of agro-industrial wastes along with possible opportunities in the bioeconomy.

Utilization of agro-industrial by-products in Monascus fermentation: a review

The Monascus fermentation industry has gained global attention. Its key products, i.e., pigments, functional food ingredients, food supplements, and medicinal use, are growing in the world's market. Efforts to find the cost-effective substrate for Monascus fermentation have remained the target. This paper aimed to appraise the utilization of agro-industrial by-products (cereal, starchy tuber and root, legume, fruit, and coffee processing) as a cost-effective substrate for Monascus fermentation. The specific objective was to review the by-products pre-treatment, the fermentation process, product yield, and the bioactivity of the fermented products. Among all the by-products that could be used as the fermentation substrate, cereal brans do not need pre-treatment, but others need a suitable pre-treatment step, e.g., cassava peel, okara, and jackfruit seed to list a few, that need to be powdered beforehand. Other substrates, such as corn cob and durian seed, need soaking and size reduction through the pre-treatment step. During fermentation, Monascus produce many pigments, monacolin K, associated with rise in phenolic and flavonoid contents. These products possess antioxidant, antihypercholesterol, antidiabetes, and antiatherosclerosis activities which underpin their health significance. In conclusion, we report in this review the agro-industrial by-products which have potential prospects for pigments, functional food ingredients, food supplements, and therapeutic usages produced from Monascus fermentation.

Natural pigment from Monascus: The production and therapeutic significance

OBJECTIVE

The present review highlights the advantages of using natural colorant over the synthetic one. We have discussed the fermentation parameters that can enhance the productivity of Monascus pigment on agricultural wastes.

BACKGROUND

Food industry is looking for natural colours because these can enhance the esthetic value, attractiveness, and acceptability of food while remaining nontoxic. Many synthetic food colours (Azorubine Carmoisine, quinoline) have been prohibited due to their toxicity and carcinogenicity. Increasing consumer awareness towards the food safety has forced the manufacturing industries to look for suitable alternatives. In addition to safety, natural colorants have been found to have nutritional and therapeutic significance. Among the natural colorants, microbial pigments can be considered as a viable option because of scalability, easier production, no seasonal dependence, cheaper raw materials and easier extraction. Fungi such as Monascus have a long history of safety and therefore can be used for production of biopigments.

METHOD

The present review summarizes the predicted biosynthetic pathways and pigment gene clusters in Monascus purpureus.

RESULTS

The challenges faced during the pilot-scale production of Monascus biopigment and taming it by us of low-cost agro-industrial substrates for solid state fermentation has been suggested.

CONCLUSION

Keeping in mind, therapeutic properties of Monascus pigments and their derivatives, they have huge potential for industrial and pharmaceutical application.

APPLICATION

Though the natural pigments have wide scope in the food industry. However, stabilization of pigment is the greatest challenge and attempts are being made to overcome this by complexion with hydrocolloids or metals and by microencapsulation.

Use of Wheat Straw for Value-Added Product Xylanase by Penicillium chrysogenum Strain A3 DSM105774

The present work highlights the valorization of the bulky recalcitrant lignocellulose byproduct wheat straw (WS) for the enhanced production of value-added xylanase by the locally sourced novel Penicillium chrysogenum strain A3 DSM105774 for the first time. The optimized production of xylanase by submerged state of fermentation of WS was achieved using a three-step statistical and sequential approach: one factor at a time (OFAT), Plackett–Burman design (PBD), and Box Behnken design (BBD). Incubation temperature (30 °C), WS, and ammonium sulphate were the key determinants prompting xylanase production; inferred from OFAT. The WS concentration (%(w/v)), yeast extract concentration (%(w/v)), and initial pH of the production medium imposed significant effects (p ≤ 0.05) on the produced xylanase, realized from PBD. The predicted levels of WS concentration, initial pH of the production medium, and yeast extract concentration provoking the ultimate xylanase levels (53.7 U/mL) with an 8.95-fold enhancement, localized by the estimated ridge of the steepest ascent of the ridge analysis path, were 3.8% (w/v), 5.1, and 0.098% (w/v), respectively; 94.7% lab validation. The current data underpin the up-scaling of xylanase production using this eco-friendly, cheap, and robust methodology for the valorization of WS into the value-added product xylanase.

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.

Agro-Industrial Residues: Eco-Friendly and Inexpensive Substrates for Microbial Pigments Production

Many commodities are abundantly produced around the world, including soybean, corn, rice sugarcane, cassava, coffee, fruits, and many others. These productions are responsible for the generation of enormous amounts of daily residues, such as cassava and sugarcane bagasses, rice husk, and coffee peel. These residues are rich sources for renewable energy and can be used as substrates for industrial interest products. Microorganisms are useful biofactories, capable of producing important primary and secondary metabolites, including alcohol, enzymes, antibiotics, pigments, and many other molecules. The production of pigments was reported in bacteria, filamentous fungi, yeasts, and algae. These natural microbial pigments are very promising because synthetic colorants present a long history of allergies and toxicity. In addition, many natural pigments present other biological activities, such as antioxidant and antimicrobial activities, that are interesting for industrial applications. The use of inexpensive substrates for the production of these metabolites is very attractive, considering that agro-industrial residues are generated in high amounts and usually are a problem to the industry. Therefore, in this article we review the production of microbial pigments using agro-industrial residues during the current decade (2010–2020), considering both submerged and solid state fermentations, wild-type and genetically modified microorganisms, laboratorial to large-scale bioprocesses, and other possible biological activities related to these pigments.

Ecofriendly conversion of algal waste into valuable plant growth-promoting rhizobacteria (PGPR) biomass

With the development of marine biorefinery concept, utilisation of algal waste during industrial processing as well as some "green tide" waste biomass has become an important research topic. In this work, a single-step microwave process was used to hydrolyse Laminaria japonica processing waste (LJW) and Enteromorpha prolifera (EP), producing a growth medium suitable for microbial cultivation. The medium contained a range of mono- and polysaccharides as well as macro- and micronutrients that could be used by the microbes. The cultivation behavior of three plant growth-promoting rhizobacteria (PGPR) strains (Bacillus subtilis strain Tpb55, Bacillus amyloliquefaciens strain Cas02, and Burkholderia pyrrocinia strain Lyc2) in the two media were investigated. LJW hydrolysate from 180 °C and EP hydrolysate from 150 °C performed better cultivation efficiency than those hydrolysates from other microwave conditions. Saccharide analysis showed that microbes metabolized some monosaccharide such as glucose, mannose during cultivation, leaving polysaccharide unused in the medium. Furthermore, hydrolysate-strain cultivation mixtures were applied to pepper growth. The EP hydrolysate-Cas02 broth showed better plant growth-promoting effect compared to other treatments, which might be attributed to the higher indole-3-acetic acid (IAA) production of Cas02 in the EP hydrolysate. This work shed lights on the conversion of algal waste to PGPR biomass as well as the co-application of algal hydrolysates- strains cultivation broth for a better plant growth promotion.

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.

Production of Bio-Based Pigments from Food Processing Industry By-Products (Apple, Pomegranate, Black Carrot, Red Beet Pulps) Using Aspergillus carbonarius

Food processing industry by-products (apple, pomegranate, black carrot, and red beet pulps) were evaluated as raw materials in pigment production by the filamentous fungi Aspergillus carbonarius. The effect of fermentation conditions (solid and submerged-state), incubation period (3, 6, 9, 12, and 15 d), initial substrate pH (4.5, 5.5, 6.5, 7.5, and 8.5), and pulp particle size (<1.4, 1.4–2.0, 2–4, and >4 mm) on fungal pigment production were tested to optimize the conditions. Pigment extraction analysis carried out under solid-state fermentation conditions showed that the maximum pigment production was determined as 9.21 ± 0.59 absorbance unit at the corresponding wavelength per gram (AU/g) dry fermented mass (dfm) for pomegranate pulp (PP) by A. carbonarius for 5 d. Moreover, the highest pigment production was obtained as 61.84 ± 2.16 AU/g dfm as yellowish brown at initial pH 6.5 with < 1.4 mm of substrate particle size for 15-d incubation period. GC×GC-TOFMS results indicate that melanin could be one of the main products as a pigment. SEM images showed that melanin could localize on the conidia of A. carbonarius.

Antioxidant Activity and Role of Culture Condition in the Optimization of Red Pigment Production by Talaromyces purpureogenus KKP Through Response Surface Methodology

The red pigment production by Talaromyces purpureogenus KKP, a soil isolate, was optimized by response surface methodology (RSM) in the present study. The cultural parameters, such as pH, temperature, dextrose, and peptone concentrations, were optimized for red pigment production using the central composite design (CCD) experimental design. A second-order quadratic model was used to calculate the relationships between the values at different levels of response. The optimum values of the selected variables under coded factors are 6.0, 27 °C, 2.25%, and 1.10% for pH, temperature, dextrose, and peptone, respectively. The selected variables were most effective in the enhancement of red pigment production at optimized culture conditions. In addition to optimization, the antioxidant activity of the pigment isolated in the present study was found to be promising with IC₅₀ value (40 µg/ml). The HRMS data revealed the identification of delphinidin, limonene, 6-hydroxymethyl-7,8-dihydropterin, D-mannose 6-phosphate, and CDP-DG (18:0/18:0). The results of the present investigation will be added to the existing literature of red pigment production and its optimization by T. purpureogenus.

Transcriptional regulation contributes more to Monascus pigments diversity in different strains than to DNA sequence variation

Monascus azaphilone pigments, including red, orange, and yellow, are world-famous food colorants. However, the pigments produced by different Monascus species vary in yields and compositions. The underlying mechanism is unclear. In this study, four wild-type Monascus strains, namely M. anka M7, M. purpureus M9, M. ruber C100, and M. aurantiacus M15, were selected as research objects according to the diversification of their pigments fermented in the same mediums and conditions. Twenty-three 3 kbp segments (300 bp overlap with adjacent segments) of the pigment gene cluster were amplified, sequenced, and assembled into the DNA sequences of the clusters. The DNA sequences of pigment biosynthetic gene clusters of the four strains showed 99.94% similarity according to the results of multiple alignment. The expression levels of 17 pigment biosynthetic genes of four strains were determined by using real-time quantitative PCR. The transcriptional regulation contributed more than the DNA sequence variation in Monascus pigments metabolism. Our result gives insight into the study of Monascus pigment biosynthesis.