Production of the secondary metabolites gamma-aminobutyric acid and monacolin K by Monascus

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.

Biosynthesis of Gamma-Aminobutyric Acid (GABA) by Lactiplantibacillus plantarum in Fermented Food Production

In recent decades, given the important role of gamma-aminobutyric acid (GABA) in human health, scientists have paid great attention to the enrichment of this chemical compound in food using various methods, including microbial fermentation. Moreover, GABA or GABA-rich products have been successfully commercialized as food additives or functional dietary supplements. Several microorganisms can produce GABA, including bacteria, fungi, and yeasts. Among GABA-producing microorganisms, lactic acid bacteria (LAB) are commonly used in the production of many fermented foods. Lactiplantibacillus plantarum (formerly Lactobacillus plantarum) is a LAB species that has a long history of natural occurrence and safe use in a wide variety of fermented foods and beverages. Within this species, some strains possess not only good pro-technological properties but also the ability to produce various bioactive compounds, including GABA. The present review aims, after a preliminary excursus on the function and biosynthesis of GABA, to provide an overview of the current uses of microorganisms and, in particular, of L. plantarum in the production of GABA, with a detailed focus on fermented foods. The results of the studies reported in this review highlight that the selection of new probiotic strains of L. plantarum with the ability to synthesize GABA may offer concrete opportunities for the design of new functional foods.

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.

GC-MS-Guided Antimicrobial Defense Responsive Secondary Metabolites from the Endophytic Fusarium solani Isolated from Tinospora cordifolia and Their Multifaceted Biological Properties

Medicinal plants are hosts to an infinite number of microorganisms, commonly referred to as endophytes which are rich in bioactive metabolites yielding favorable biological activities. The endophytes are known to have a profound impact on their host plant by promoting the accumulation of secondary metabolites which are beneficial to humankind. In the present study, the fungal endophyte, Fusarium solani (ABR4) from the medicinal plant Tinospora cordifolia, was assessed for its bioactive secondary metabolites employing fermentation on a solid rice medium. The crude ABR4 fungal extract was sequentially purified using the solvent extraction method and characterized using different spectroscopic and analytical techniques namely TLC, UV spectroscopic analysis, HRESI-MS, FTIR, and GC-MS analysis. The GC-MS analysis revealed the presence of pyridine, benzoic acid, 4-[(trimethylsilyl)oxy]-trimethylsilyl ester, hexadecanoic acid trimethylsilyl ester, and oleic acid trimethylsilyl ester. The cytotoxic ability of ABR4 was evaluated by MTT assay against lung cancer (A549) and breast cancer (MCF-7) cell lines. The compounds did not exhibit significant cytotoxicity against the tested cell lines. The endophytic ABR4 extract was evaluated for its antimicrobial potential against human pathogens (S. aureus, B. cereus, E. coli, S. typhimurium, P. aeruginosa, and C. albicans) by recording 47 to 54% inhibition. Taken together, the endophytic fungal strain ABR4 demonstrated a remarkable antimicrobial activity against the tested pathogens. Furthermore, the functional metabolites isolated from the endophytic strain ABR4 reveal its broader usage as antimicrobial agents for newer drug development in the pharmaceutical industry.

An oxidoreductase gene CtnD involved in citrinin biosynthesis in Monascus purpureus verified by CRISPR/Cas9 gene editing and overexpression

Monascus produces a kind of mycotoxin, citrinin, whose synthetic pathway is still not entirely clear. The function of CtnD, a putative oxidoreductase located upstream of pksCT in the citrinin gene cluster, has not been reported. In this study, the CtnD overexpressed strain and the Cas9 constitutively expressed chassis strain were obtained by genetic transformation mediated by Agrobacterium tumefaciens. The pyrG and CtnD double gene-edited strains were then obtained by transforming the protoplasts of the Cas9 chassis strain with in vitro sgRNAs. The results showed that overexpression of CtnD resulted in significant increases in citrinin content of more than 31.7% and 67.7% in the mycelium and fermented broth, respectively. The edited CtnD caused citrinin levels to be reduced by more than 91% in the mycelium and 98% in the fermented broth, respectively. It was shown that CtnD is a key enzyme involved in citrinin biosynthesis. RNA-Seq and RT-qPCR showed that the overexpression of CtnD had no significant effect on the expression of CtnA, CtnB, CtnE, and CtnF but led to distinct changes in the expression of acyl-CoA thioesterase and two MFS transporters, which may play an unknown role in citrinin metabolism. This study is the first to report the important function of CtnD in M. purpureus through a combination of CRISPR/Cas9 editing and overexpression.

Effects of fungal based bioactive compounds on human health: Review paper

Since the first years of history, microbial fermentation products such as bread, wine, yogurt and vinegar have always been noteworthy regarding their nutritional and health effects. Similarly, mushrooms have been a valuable food product in point of both nutrition and medicine due to their rich chemical components. Alternatively, filamentous fungi, which can be easier to produce, play an active role in the synthesis of some bioactive compounds, which are also important for health, as well as being rich in protein content. Therefore, this review presents some important bioactive compounds (bioactive peptides, chitin/chitosan, β-glucan, gamma-aminobutyric acid, L-carnitine, ergosterol and fructooligosaccharides) synthesized by fungal strains and their health benefits. In addition, potential probiotic- and prebiotic fungi were researched to determine their effects on gut microbiota. The current uses of fungal based bioactive compounds for cancer treatment were also discussed. The use of fungal strains in the food industry, especially to develop innovative food production, has been seen as promising microorganisms in obtaining healthy and nutritious food.

Optimization of the hongqu starter preparation process for the manufacturing of red mold rice with high gamma-aminobutyric acid production by solid-state fermentation

Red mold rice (RMR) generally contains gamma-aminobutyric acid (GABA), which has several physiological functions. Monascus purpureus M162, with a high GABA production of 15.10 mg/g was generated by atmospheric and room temperature plasma mutation. Furthermore, we conducted a response surface methodology to produce a premium hongqu starter. The results revealed that under optimal conditions, that is, a substrate containing brown rice and bran in a brown rice: bran ratio of 9:1 (wt/wt), an inoculation size of 21.50 mL/100 g, a mixing frequency of one time/9 h, and a cultivation time of 7.20 days, the number of active spores, α-amylase activity, and saccharification power activity was 4.15 × 10⁷ spores/g, 155 U/g, and 3260 U/g in the high-quality starter, respectively. These values were 224.32-fold, 139.64%, and 141.74% higher than those obtained with M. purpureus M162 inoculated into steamed indica rice, respectively, and 153.70-fold, 267.24%, and 151.63% higher than those obtained with the parent strain M. purpureus M1, respectively. The premium hongqu starter of M. purpureus M162 was inoculated into steamed indica rice to produce RMR with 15.93 mg/g of GABA. In conclusion, we proposed a novel strategy for functional RMR production with high GABA concentrations by solid-state fermentation with Monascus spp.

Effect of Sodium Selenite on the Metabolite Profile of Epichloë sp. Mycelia from Festuca sinensis in Solid Culture

Selenium (Se) is an essential micronutrient with many beneficial effects for humans and other living organisms. Numerous microorganisms in culture systems enrich and convert inorganic selenium to organic selenium. In this study, Epichloë sp. from Festuca sinensis was exposed to increasing Na2SeO3 concentrations (0, 0.1, 0.2, 0.3, and 0.4 mmol/L) in Petri dishes with potato dextrose agar (PDA) for 8 weeks. Epichloë sp. mycelia were immediately collected after mycelial diameters were measured at 4, 5, 6, 7, and 8 weeks of cultivation, respectively. Gas chromatography-mass spectrometer (GC-MS) analysis was performed on different groups of Epichloë sp. mycelia. Different changes were observed as Epichloë sp. was exposed to different selenite conditions and cultivation time. The colony diameter of Epichloë sp. decreased in response to increased selenite concentrations, whereas the inhibitory effects diminished over time. Seventy-two of the 203 identified metabolites did not differ significantly across selenite treatments within the same time point, while 82 compounds did not differ significantly between multiple time points of the same Se concentration. However, the relative levels of 122 metabolites increased the most under selenite conditions. Specifically, between the 4th and 8th weeks, there were increases in 2-keto-isovaleric acid, uridine, and maltose in selenite treatments compared to controls. Selenium increased glutathione levels and exhibited antioxidant properties in weeks 4, 5, and 7. Additionally, we observed that different doses of selenite could promote the production of carbohydrates such as isomaltose, cellobiose, and sucrose; fatty acids such as palmitoleic acid, palmitic acid, and stearic acid; and amino acids such as lysine and tyrosine in Epichloë sp. mycelia. Therefore, Epichloë sp. exposed to selenite stress may benefit from increased levels of some metabolite compounds.

Production of Lovastatin using Liquid Cheese Whey by Fusarium nectrioides (MH173849), an Endophytic Fungi Isolated from Euphorbia hirta

Lovastatin is a naturally produced 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase enzyme inhibitor- used for treating hypercholesterolemia. It was the first statin drug which was approved by the United States Food and Drug Administration (USFDA). In the current study, endophytic fungus Fusarium nectrioides (MH173849) isolated from Euphorbia hirta L. was used for the production of lovastatin. Four different culture media indicated as M1, M2, M3 and M4 were used for the initial production of lovastatin. Liquid cheese whey was used as nitrogen source. Growth morphology of fungi was investigated using Scanning Electron Microscopy analysis. Also, parameters like temperature, pH, inoculum size, incubation time, and RPM were optimized for the obtaining highest lovastatin production. Among the four media, M4 was found to produce the maximum concentration of lovastatin. Parameters such as temperature of 28°C, pH 6, RPM – 180 rpm and inoculum size of 5 x107 spores/mL were optimal for the production of lovastatin by F. nectrioides (MH173849).

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.

Azaphilone alkaloids: prospective source of natural food pigments

Azaphilone, biosynthesized by polyketide synthase, is a class of fungal metabolites. In this review, after brief introduction of the natural azaphilone diversity, we in detail discussed azaphilic addition reaction involving conversion of natural azaphilone into the corresponding azaphilone alkaloid. Then, setting red Monascus pigments (a traditional food colorant in China) as example, we presented a new strategy, i.e., interfacing azaphilic addition reaction with living microbial metabolism in a one-pot process, to produce azaphilone alkaloid with a specified amine residue (red Monascus pigments) during submerged culture. Benefit from the red Monascus pigments with a specified amine residue, the influence of primary amine on characteristics of the food colorant was highlighted. Finally, the progress for screening of alternative azaphilone alkaloids (production from interfacing azaphilic addition reaction with submerged culture of Talaromyces sp. or Penicillium sp.) as natural food colorant was reviewed. KEY POINTS: • Azaphilic addition reaction of natural azaphilone is biocompatible • Red Monascus pigment is a classic example of azaphilone alkaloids • Azaphilone alkaloids are alterative natural food colorant.

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.

Protective effect and mechanism of Monascus-fermented red yeast rice against colitis caused by Salmonella enterica serotype Typhimurium ATCC 14028

Red yeast rice (RYR), a traditional Chinese fermented food, has the effect of lowering blood lipid and cholesterol, but little information is available about whether RYR can inhibit pathogenic bacterial infection in vivo. The present study explored the effect of RYR on Salmonella enterica-induced intestinal inflammation and gut microbiota dysbiosis in mice as well as the underlying anti-inflammatory mechanism. Results showed that RYR can alleviate S. enterica infection in vivo and Monascus pigments are the main functional components. The analysis of microbiota, gene expression profile and serological immunology revealed that RYR can regulate the intestinal flora and increase the relative abundance of beneficial bacteria such as Lactobacillus and Akkermansia. Meanwhile, RYR is also found to regulate the expression of pro-inflammatory factors and tight junction-related genes to inhibit the NO and NF-κB-mediated inflammatory response and maintain the integrity of the intestinal barrier. This study provides a new dietary intervention strategy for the prevention of pathogenic bacterial infection.

A Review of Red Yeast Rice, a Traditional Fermented Food in Japan and East Asia: Its Characteristic Ingredients and Application in the Maintenance and Improvement of Health in Lipid Metabolism and the Circulatory System

Red yeast rice has been used to produce alcoholic beverages and various fermented foods in China and Korea since ancient times; it has also been used to produce tofuyo (Okinawan-style fermented tofu) in Japan since the 18th century. Recently, monacolin K (lovastatin) which has cholesterol-lowering effects, was found in some strains of Monascus fungi. Since statins have been used world-wide as a cholesterol-lowering agent, processed foods containing natural statins are drawing attention as materials for primary prevention of life-style related diseases. In recent years, large-scale commercial production of red yeast rice using traditional solid-state fermentation has become possible, and various useful materials, including a variety of monascus pigments (polyketides) that spread as natural pigments, in addition to statins, are produced in the fermentation process. Red yeast rice has a lot of potential as a medicinal food. In this paper, we describe the history of red yeast rice as food, especially in Japan and East Asia, its production methods, use, and the ingredients with pharmacological activity. We then review evidence of the beneficial effects of red yeast rice in improving lipid metabolism and the circulatory system and its safety as a functional food.

Bioactive Pigments of Monascus purpureus Attributed to Antioxidant, HMG-CoA Reductase Inhibition and Anti-atherogenic Functions

Monascus purpureus is known to produce pigment molecules. The pigments were extracted from M. purpureus fermented rice. In-vitro antioxidant effects of pigments were observed and presumed to alleviate oxidative stress related atherosclerosis effect in rats fed with high fat diet (HFD) for 14 weeks. The formation of lipid peroxide due to the oxidation of serum lipid was higher in rats fed with HFD. While, the feeding of fermented rice (groups III-V) significantly lowered the formation of lipid peroxide (27.1–51.7%) in serum of rats, indicated antioxidative effect of pigments. In addition, feeding of fermented rice lowered serum cholesterol and triacylglycerol by 44.82 and 45.30%, respectively. Whereas, LDL-cholesterol levels were decreased by 70.12% and HDL-cholesterol increased by 34.58%. The atherogenic indices (LDL/HDL and TC/HDL) were reduced by 77.80 and 61.05%, respectively, in rats fed with fermented rice. These data confirmed the anti-atherosclerotic effect of pigments. Further liver enzyme, 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase activity was significantly inhibited up to 54%. The identification of statins, sterols and fatty acids in fermented rice revealed the HMG-CoA reductase inhibitory activity. This was confirmed by synthesis of lower levels of cholesterol and triacylglycerol in liver of rats fed with fermented rice. Accordingly antioxidant, inhibition of HMG-CoA reductase, anti-atherogenic functions of M. purpureus fermented rice is attributed to the collective effect of bioactive metabolites.

Microbial production of gamma-aminobutyric acid: applications, state-of-the-art achievements, and future perspectives

Gamma-aminobutyric acid (GABA) is an important non-protein amino acid with wide-ranging applications. Currently, GABA can be produced by a variety of methods, including chemical synthesis, plant enrichment, enzymatic methods, and microbial production. Among these methods, microbial production has gained increasing attention to meet the strict requirements of an additive in the fields of food, pharmaceutical, and livestock. In addition, renewable and abundant resources, such as glucose and lignocellulosic biomass can also be used for GABA microbial production under mild and environmentally friendly processing conditions. In this review, the applications, metabolic pathways and physiological functions of GABA in different microorganisms were firstly discussed. A comprehensive overview of the current status of process engineering strategies for enhanced GABA production, including fermentation optimization and whole-cell conversion from different feedstocks by various host strains is also provided. We also presented the state-of-the-art achievements in strain development strategies for industrial lactic acid bacteria (LAB), Corynebacterium glutamicum and Escherichia coli to enhance the performance of GABA bioproduction. In order to use bio-based GABA in the fields of food and pharmaceutical, some Generally Recognized as Safe (GRAS) strains such as LAB and C. glutamicum will be the promising chassis hosts. Toward the end of this review, current challenges and valuable research directions/strategies on the improvements of process and strain engineering for economic microbial production of GABA are also suggested.

Metabolomics Analysis of the Effect of Glutamic Acid on Monacolin K Synthesis in Monascus purpureus

Monacolin K is a secondary metabolite produced by Monascus with beneficial effects on health, including the ability to lower cholesterol. We previously showed that the yield of monacolin K was significantly improved when glutamic acid was added to the fermentation broth of Monascus purpureus M1. In this study, we analyzed M. purpureus in media with and without glutamic acid supplementation using a metabolomic profiling approach to identify key metabolites and metabolic pathway differences. A total of 817 differentially expressed metabolites were identified between the two fermentation broths on day 8 of fermentation. Pathway analysis of these metabolites using the KEGG database indicated overrepresentation of the citric acid cycle; biotin metabolism; and alanine, aspartate, and glutamate metabolic pathways. Six differentially expressed metabolites were found to be related to the citric acid cycle. The effect of citric acid as an exogenous additive on the synthesis of monacolin K was examined. These results provide technical support and a theoretical basis for further studies of the metabolic regulatory mechanisms underlying the beneficial effects of monacolin K and medium optimization, as well as genetic engineering of Monascus M1 for efficient monacolin K production.

Perspectives on Functional Red Mold Rice: Functional Ingredients, Production, and Application

Monacolin K (MK) is a secondary metabolite of the Monascus species that can inhibit cholesterol synthesis. Functional red mold rice (FRMR) is the fermentation product of Monascus spp., which is rich in MK. FRMR is usually employed to regulate serum cholesterol, especially for hypercholesterolemic patients who refuse statins or face statin intolerance. The present perspective summarized the bioactive components of FRMR and their functions. Subsequently, efficient strategies for FRMR production, future challenges of FRMR application, and possible directions were proposed. This perspective helps to understand the present situation and developmental prospects of FRMR.

Regulation of secondary metabolite biosynthesis in Monascus purpureus via cofactor metabolic engineering strategies

This study investigated the effects of cofactor metabolism on secondary metabolite production in M. purpureus through the application of different cofactor engineering strategies. Total pigment production dramatically increased by 39.08% and 40.89%, and yellow pigment production increased by 74.62% and 114.06% after the addition of 1.0 mg/L of the exogenous cofactor reagents methyl viologen and rotenone, respectively, in submerged batch-fermentation. The extracellular red pigment tone changed to yellow with the application of electrolytic stimulation at 800 mV/cm², but almost no citrinin production was detected. In addition, the total pigment, yellow pigment and citrinin production increased by 35.46%, 54.89% and 6.27% after disruption of the nuoⅠ gene that encodes NADH-quinone oxidoreductase, respectively. Thus, cofactor metabolic engineering strategies could be extended to the industrial production of Monascus pigment or high yellow pigment with free citrinin production.

Exposure to greenspaces could reduce the high global burden of pain

Painful conditions are among the leading causes of years lived with disability, and may increase following the coronavirus pandemic, which has led to temporary closure of some healthcare services for people with chronic pain. To reduce this burden, novel, cost-effective and accessible interventions are required. We propose that greenspace exposure may be one such intervention. Drawing on evidence from neuroscience, physiology, microbiology, and psychology, we articulate how and why exposure to greenspaces could improve pain outcomes and reduce the high global burden of pain. Greenspace exposure potentially provides opportunities to benefit from known or proposed health-enhancing components of nature, such as environmental microbiomes, phytoncides, negative air ions, sunlight, and the sights and sounds of nature itself. We review the established and potential links between these specific exposures and pain outcomes. While further research is required to determine possible causal links between greenspace exposure and pain outcomes, we suggest that there is already sufficient evidence to help reduce the global burden of pain by improving access and exposure to quality greenspaces.

Targeting the microbiota in pharmacology of psychiatric disorders

There is increasing interest in the role of the gut microbiota in health and disease. In particular, gut microbiota influences the Central Nervous System (CNS) development and homeostasis through neural pathways or routes involving the immune and circulatory systems. The CNS, in turn, shapes the intestinal flora through endocrine or stress-mediated responses. These overall bidirectional interactions, known as gut microbiota-brain axis, profoundly affect some brain functions, such as neurogenesis and the production of neurotransmitters, up to influence behavioral aspects of healthy subjects. Consequently, a dysfunction within this axis, as observed in case of dysbiosis, can have an impact on the behavior of a given individual (e.g. anxiety and depression) or on the development of pathologies affecting the CNS, such as autism spectrum disorders and neurodegenerative diseases (e.g. Alzheimer's disease and Parkinson's disease). It should be considered that the whole microbiota has a significant role not only on aspects concerning human physiology, such as harvesting of nutrients and energy from the ingested food or production of a wide range of bioactive compounds, but also has positive effects on the gastrointestinal barrier function and actively contributes to the pharmacokinetics of several compounds including neuropsychiatric drugs. Indeed, the microbiota is able to affect drug absorption and metabolism up to have an impact on drug activity and/or toxicity. On the other hand, drugs are able to shape the human gut microbiota itself, where these changes may contribute to their pharmacologic profile. Therefore, the emerging picture on the complex drug-microbiota bidirectional interplay will have considerable implications in the future not only in terms of clinical practice but also, upstream, on drug development.

Development of an Improved Menopausal Symptom-Alleviating Licorice (Glycyrrhiza uralensis) by Biotransformation Using Monascus albidulus

Licorice (Glycyrrhiza uralensis) contains several compounds that have been reported to alleviate menopausal symptoms via interacting with estrogen receptors (ERs). The compounds exist mainly in the form of glycosides, which exhibit low bioavailability and function. To bioconvert liquiritin and isoliquiritin, the major estrogenic compounds, to the corresponding deglycosylated liquiritigenin and isoliquiritigenin, respectively, licorice was fermented with Monascus, which has been demonstrated to deglycosylate other substances. The contents of liquiritigenin and isoliquiritigenin in Monascus-fermented licorice increased by 10.46-fold (from 38.03 µM to 379.75 µM) and 12.50-fold (from 5.53 µM to 69.14 µM), respectively, compared with their contents in non-fermented licorice. Monascus-fermented licorice exhibited 82.5% of the ERβ binding activity of that observed in the positive control (17 β-estradiol), whereas the non-fermented licorice exhibited 54.1% of the binding activity in an in vivo ER binding assay. The increase in the ERβ binding activity was associated with increases in liquiritigenin and isoliquiritigenin contents. Liquiritigenin acts as a selective ligand for ERβ, which alleviates menopausal symptoms with fewer side effects, such as heart disease and hypertension, compared with a ligand for ERα. In addition, Monascus-fermented licorice contained 731 mg/kg of monacolin K, one of the metabolites produced by Monascus that reduces serum cholesterol. Therefore, Monascus-fermented licorice is a promising material for the prevention and treatment of menopausal syndrome with fewer side effects.

An overview of Monascus fermentation processes for monacolin K production

In Asia, Monascus has been used in food fermentation for nearly a thousand years. It has attracted increasing attention in recent years due to its ability to produce a variety of important active substances such as monacolin K (MK) and pigments. MK is an effective drug widely used for lowering human blood cholesterol that functions by inhibiting the rate-limiting enzyme in cholesterol biosynthesis. Monascus strains, fermentation methods and fermentation conditions have significant effects on MK yield, and much research has been undertaken to obtain higher MK yields. In this paper, the research progress of Monascus strain breeding for high MK yield, medium optimization for MK production during Monascus fermentation, and optimization of fermentation process conditions are fully reviewed. This provides reference for future research on Monascus fermentation and industrial production for high-yield MK production.

A Brief Review on the Non-protein Amino Acid, Gamma-amino Butyric Acid (GABA): Its Production and Role in Microbes

Gamma-Aminobutyric acid (GABA) is a non-protein amino acid widely distributed in nature. It is produced through irreversible α-decarboxylation of glutamate by enzyme glutamate decarboxylase (GAD). GABA and GAD have been found in plants, animals, and microorganisms. GABA is distributed throughout the human body and it is involved in the regulation of cardiovascular conditions such as blood pressure and heart rate, and plays a role in the reduction of anxiety and pain. Although researchers had produced GABA by chemical method earlier it became less acceptable as it pollutes the environment. Researchers now use a more promising microbial method for the production of GABA. In the drug and food industry, demand for GABA is immense. So, large scale conversion of GABA by microbes has got much attention. So this review focuses on the isolation source, production, and functions of GABA in the microbial system. We also summarize the mechanism of action of GABA and its shunt pathway.

Use of Selected Lactobacilli to Increase γ-Aminobutyric Acid (GABA) Content in Sourdough Bread Enriched with Amaranth Flour

γ-Aminobutyric acid (GABA) is the primary inhibitory neurotransmitter of the central nervous system and possesses various physiological functions. GABA production can be obtained thanks to lactic acid bacteria activity in different foods such as sourdoughs. Recently, breads made from blends of pseudocereals and wheat flours have attracted much attention. Amaranth is especially interesting because of its high nutritional value, having a high protein content and containing different antioxidant compounds. Therefore, this study aimed to obtain sourdough breads enriched with GABA thanks to bacterial activity and to investigate the effect of amaranth flour addition on the antioxidant and sensorial properties of bread. Eighteen lactobacilli strains were assayed for GABA production in amaranth and wheat flour liquid sourdoughs. Two strains, Lactobacillus brevis A7 and Lactobacillus farciminis A11, demonstrated high GABA producing capability; hence, they were used to prepare breads containing 20% amaranth flour. The results confirmed the capability of the two strains to increase GABA concentrations (up to 39 mg/kg) in breads. Samples with amaranth addition showed a significantly higher total phenolic content compared to the control bread (more than 15 mg GAE 100 g^-1 dwb); sensory analysis showed that breads with amaranth were moderately acceptable. Nevertheless, their general liking evaluation was significantly lower compared to the control bread. The addition of pseudocereal to traditional wheat sourdough and selection of lactobacilli allowed the production of baked goods with enhanced GABA content and antioxidant capacity, but recipes have to be developed to increase the organoleptic acceptability of the final products.

Neurotransmitter modulation by the gut microbiota

The gut microbiota - the trillions of bacteria that reside within the gastrointestinal tract - has been found to not only be an essential component immune and metabolic health, but also seems to influence development and diseases of the enteric and central nervous system, including motility disorders, behavioral disorders, neurodegenerative disease, cerebrovascular accidents, and neuroimmune-mediated disorders. By leveraging animal models, several different pathways of communication have been identified along the "gut-brain-axis" including those driven by the immune system, the vagus nerve, or by modulation of neuroactive compounds by the microbiota. Of the latter, bacteria have been shown to produce and/or consume a wide range of mammalian neurotransmitters, including dopamine, norepinephrine, serotonin, or gamma-aminobutyric acid (GABA). Accumulating evidence in animals suggests that manipulation of these neurotransmitters by bacteria may have an impact in host physiology, and preliminary human studies are showing that microbiota-based interventions can also alter neurotransmitter levels. Nonetheless, substantially more work is required to determine whether microbiota-mediated manipulation of human neurotransmission has any physiological implications, and if so, how it may be leveraged therapeutically. In this review this exciting route of communication along the gut-brain-axis, and accompanying data, are discussed.

Quality and Authenticity Control of Functional Red Yeast Rice-A Review

Red yeast rice (RYR) is made by fermenting the rice with Monascus. It is commonly used in food colorants, dyeing, and wine making in China and its neighboring countries. Nowadays RYR has two forms on the market: common RYR is used for food products, the other form is functional RYR for medicine. However, some researchers reported that commercial lovastatin (structure is consistent with monacolin K) is illegally added to common RYR to meet drug quality standards, so as to imitate functional RYR and sell the imitation at a higher price. Based on current detection methods, it is impossible to accurately distinguish whether functional RYR is adulterated. Therefore, it is especially important to find a way to authenticate functional RYR. In the current review, the advances in history, applications, components (especially monacolins, monacolins detection methods), quality standards, authentication methods and perspectives for the future study of RYR are systematically reviewed.

NaCl Inhibits Citrinin and Stimulates Monascus Pigments and Monacolin K Production

Applications of beneficial secondary metabolites produced by Monascus purpureus (M. purpureus) could be greatly limited for citrinin, a kidney toxin. The link of NaCl with cell growth and secondary metabolites in M. purpureus was analyzed with supplementations of different concentrations of NaCl in medium. The content of citrinin was reduced by 48.0% but the yellow, orange, red pigments and monacolin K productions were enhanced by 1.7, 1.4, 1.4 and 1.4 times, respectively, compared with those in the control using NaCl at 0.02 M at the 10th day of cultivation. NaCl didn’t affect the cell growth of M. purpureus. This was verified through the transcriptional up-regulation of citrinin synthesis genes (pksCT and ctnA) and the down-regulation of the Monascus pigments (MPs) synthesis genes (pksPT and pigR). Moreover, the reactive oxygen species (ROS) levels were promoted by NaCl at the 2nd day of cultivation, and then inhibited remarkably with the extension of fermentation time. Meanwhile, the activities of superoxide dismutase (SOD) and catalase (CAT), and the contents of total glutathione (T-GSH) were significantly enhanced in the middle and late stages of cultivation. The inhibition effect on colony size and the growth of aerial mycelia was more obvious with an increased NaCl concentration. Acid and alkaline phosphatase (ACP and AKP) activities dramatically increased in NaCl treatments. NaCl could participate in secondary metabolites synthesis and cell growth in M. purpureus.

Lactobacillus brevis CGMCC 1306 glutamate decarboxylase: Crystal structure and functional analysis

Glutamate decarboxylase (GAD), which is a unique pyridoxal 5-phosphate (PLP)-dependent enzyme, can catalyze α-decarboxylation of l-glutamate (L-Glu) to γ-aminobutyrate (GABA). The crystal structure of GAD in complex with PLP from Lactobacillus brevis CGMCC 1306 was successfully solved by molecular-replacement, and refined at 2.2 Å resolution to an R_work factor of 18.76% (R_free = 23.08%). The coenzyme pyridoxal 5-phosphate (PLP) forms a Schiff base with the active-site residue Lys279 by continuous electron density map, which is critical for catalysis by PLP-dependent decarboxylase. Gel filtration showed that the active (pH 4.8) and inactive (pH 7.0) forms of GAD are all dimer. The residues (Ser126, Ser127, Cys168, Ile211, Ser276, His278 and Ser321) play important roles in anchoring PLP cofactor inside the active site and supporting its catalytic reactivity. The mutant T215A around the putative substrate pocket displayed an 1.6-fold improvement in catalytic efficiency (k_cat/K_m) compared to the wild-type enzyme (1.227 mM^-1 S^-1 versus 0.777 mM^-1 S^-1), which was the highest activity among all variants tested. The flexible loop (Tyr308-Glu312), which is positioned near the substrate-binding site, is involved in the catalytic reaction, and the conserved residue Tyr308 plays a vital role in decarboxylation of L-Glu.

Investigation of Citrinin and Pigment Biosynthesis Mechanisms in Monascus purpureus by Transcriptomic Analysis

Monascus purpureus YY-1 is widely used in food colorant production in China. Our previous study clearly illustrated the whole-genome data for YY-1 and provided useful insight into evolutionary research and industrial applications. However, the presence of citrinin, which has nephrotoxic, hepatotoxic, and carcinogenic activities, has attracted attention to the safety of Monascus products. In an effort to reduce the harmful effects of citrinin in Monascus-related products, a random mutant of M. purpureus YY-1 with low citrinin production (designated as "winter") was obtained in this study. To analyze the biosynthesis and regulation mechanisms of pigment and citrinin, a transcriptomic analysis of the M. purpureus YY-1 and winter strains was performed. Comparative transcriptomic analysis reveals pksCT, the essential gene for citrinin synthesis, showed a low expression level in M. purpureus YY-1 and winter, which suggested there might be isoenzymes in M. purpureus YY-1 that were responsible for the citrinin synthesis during evolution. In addition, changes in transcription factor expression may also influence the network regulating the citrinin synthesis pathway in M. purpureus. Moreover, the yields of pigments produced by the winter mutant were significantly increased. Repressing the central carbon metabolism and improving the acetyl-CoA pool can contribute to a high pigment yield, and enhanced NADPH regeneration can also lead to the metabolic flux of pigment production in M. purpureus. Investigations into the biosynthesis and regulation of citrinin and pigment production in M. purpureus will enhance our knowledge of the mechanisms behind the biosynthesis of fungal secondary metabolites.

MptriA, an Acetyltransferase Gene Involved in Pigment Biosynthesis in M. purpureus YY-1

Monascus pigments (Mps) have been used as food colorants for several centuries in Asian countries. MptriA is a putative acetyltransferase gene involved in the MPs biosynthesis. To analyze the function of MptriA, an MptriA disruption strain (Δ MptriA) and a complementation strain (Δ MptriA:: MptriA) were successfully obtained In addition to the loss of color, the disruption of MptriA had little effect on the phenotypes during growth on four different media. The Δ MptriA strain showed decreased pigment and citrinin production during the liquid-fermentation process. Transcriptional analysis showed that the expression of several genes involved in the synthesis of pigments and citrinin was down-regulated in Δ MptriA. These results demonstrated that the role of MptriA was to transfer an acyl group to the pyranoquinone structure of the polyketide chromophore during Monascus pigment biosynthesis and to influence the citrinin biosynthesis pathway. This study contributes to the exploration of pigment biosynthesis in M. purpureus.

Improvement of skin conditions by ingestion of Aspergillus kawachii (Koji) extract containing 14-dehydroergosterol in a randomized, double-blind, controlled trial

Purpose

The present study examined the effect of ingestion of Koji extract containing 14-dehydroergosterol (14-DHE), prepared from Aspergillus kawachii NBRC4308, on improvement of skin conditions among healthy volunteers.

Subjects and methods

In a randomized, double-blind, placebo-controlled, parallel-group study, 70 healthy adult women who felt that their skin was dry ingested either a placebo dietary supplement or Koji extract (200 mg/day) supplement containing 0.1% 14-DHE for 12 weeks. Throughout the treatment period and for 4 weeks afterward, objective indicators - including moisture content of the stratum corneum, trans-epidermal water loss (TEWL), and skin wrinkles - were evaluated; in addition, the subjects answered a questionnaire on their skin conditions with ratings on a visual analog scale. Statistical analysis was conducted on the basis of differences from baseline scores.

Results

Compared with the placebo group, the Koji extract group showed significantly increased forearm moisture at 4, 8, and 16 weeks (p < 0.05 on unpaired t-test). The questionnaire survey showed a marked improvement in skin conditions, particularly crow's feet, in the Koji extract group versus the placebo group at 8 weeks (p < 0.05 by unpaired t-test). Furthermore, the Koji extract group showed a trend (p < 0.10) toward improvement in skin moisture (at 4 weeks), dryness around the eyes/mouth (at 4 weeks), and overall skin condition (at 8 weeks) versus the placebo group.

Conclusion

Ingestion of Koji extract containing 14-DHE was demonstrated to have positive effects toward improving skin conditions - in particular, on increasing skin moisture in the stratum corneum.

Monascus-fermented red mold dioscorea protects mice against alcohol-induced liver injury, whereas its metabolites ankaflavin and monascin regulate ethanol-induced peroxisome proliferator-activated receptor-γ and sterol regulatory element-binding transcription factor-1 expression in HepG2 cells

BACKGROUND

Alcoholic hepatitis is a necroinflammatory process that is associated with fibrosis and leads to cirrhosis in 40% of cases. The hepatoprotective effects of red mold dioscorea (RMD) from Monascus purpureus NTU 568 were evaluated in vivo using a mouse model of chronic alcohol-induced liver disease (ALD).

RESULTS

ALD mice were orally administered vehicle (ALD group) or vehicle plus 307.5, 615.0 or 1537.5 mg kg^-1 (1 ×, 2 × and 5 ×) RMD for 5 weeks. RMD lowered serum leptin, hepatic total cholesterol, free fatty acid and hepatic triglyceride levels and increased serum adiponectin, hepatic alcohol dehydrogenase and antioxidant enzyme levels. Furthermore, ankaflavin (AK) and monascin (MS), metabolites of RMD fermented with M. purpureus 568, induced peroxisome proliferator-activated receptor-γ expression and the concomitant suppression of ethanol-induced elevation of sterol regulatory element-binding transcription factor-1 and TG in HepG2 cells.

CONCLUSION

These results indicate the hepatoprotective effect of Monascus-fermented RMD. Moreover, AK and MS were identified as the active constituents of RMD for the first time and were shown to protect against ethanol-induced liver damage. © 2017 Society of Chemical Industry.

Evaluation of a Malaysian soy sauce koji strain Aspergillus oryzae NSK for γ-aminobutyric acid (GABA) production using different native sugars

In this study, a selected γ-aminobutyric acid (GABA)-rich Malaysian strain Aspergillus oryzae NSK was collected from soy sauce koji. The strain was used to explore the effect of using renewable native sugar syrup, sugarcane, nipa, and molasses as fermentable substrates for developing a novel functional GABA soy sauce. We evaluated the strain using the chosen native sugars for 7 days using shake flask fermentation at 30 °C. The results showed optimum GABA concentration was achieved using cane molasses as the fermentable substrate (354.08 mg/L), followed by sugarcane syrup (320.7 mg/L) and nipa syrup (232.07 mg/L). Cane molasses was subsequently utilized as a substrate to determine the most suitable concentration for A. oryzae NSK to enhance GABA production and was determined as 50% g/L of glucose standard cane molasses. Our findings indicate that cane molasses can be used as a GABA-rich ingredient to develop a new starter culture for A. oryzae NSK soy sauce production.

Glutamic acid promotes monacolin K production and monacolin K biosynthetic gene cluster expression in Monascus

This study investigated the effects of glutamic acid on production of monacolin K and expression of the monacolin K biosynthetic gene cluster. When Monascus M1 was grown in glutamic medium instead of in the original medium, monacolin K production increased from 48.4 to 215.4 mg l⁻¹, monacolin K production increased by 3.5 times. Glutamic acid enhanced monacolin K production by upregulating the expression of mokB-mokI; on day 8, the expression level of mokA tended to decrease by Reverse Transcription-polymerase Chain Reaction. Our findings demonstrated that mokA was not a key gene responsible for the quantity of monacolin K production in the presence of glutamic acid. Observation of Monascus mycelium morphology using Scanning Electron Microscope showed glutamic acid significantly increased the content of Monascus mycelium, altered the permeability of Monascus mycelium, enhanced secretion of monacolin K from the cell, and reduced the monacolin K content in Monascus mycelium, thereby enhancing monacolin K production.

Comparison of the elution characteristics of individual forms of lovastatin in both isocratic and gradient modes and HPLC-PDA method development for pure and fermentation-derived lovastatin

The elution characteristics of lovastatin were studied by varying the composition of mobile phase in both isocratic and gradient elution modes to comprehend the role of organic modifier and acidifier on the overall analysis time and retention time of individual forms of lovastatin. Acetonitrile has influenced on the overall analysis time, whereas the acidifier determines the retention time of hydroxy acid form of lovastatin and the retention time gap between the individual forms. A combination of acetonitrile and 0.1% trifluoroacetic acid (TFA) (60:40, v/v) in isocratic elution mode eluted both hydroxy acid and lactone forms of lovastatin at 4.5 and 5.4 min, respectively. This appears to be a better approach for the separation of pharmaceutical and clinical lovastatin samples. At isocratic elution mode, a mixture of acetonitrile and either 0.05% TFA or 0.1% H₃PO₄ of 60:40 (v/v) has eluted both hydroxy acid and lactone forms of lovastatin at 10 ± 0.5 and 17 ± 0.5 min, respectively. This is suitable for the fermentation-derived samples or for the complex mixtures of structural analogs. The fermentation broth (pH not adjusted) extracted with ethyl acetate at a ratio of 1:1 (v/v) at 60°C for 30 min was the optimal extraction condition for lovastatin.

Alleviation of metabolic syndrome by monascin and ankaflavin: the perspective of Monascus functional foods

The metabolites of Monascus with multiple benefits are popular subjects for the development of functional foods. The yellow pigments, monascin and ankaflavin, which are the constituent metabolites of M. purpureus, M. pilosus and M. ruber, are becoming the focus of research on Monascus. Monascin and ankaflavin are azaphilone compounds with similar structures that exhibit multiple beneficial effects including anti-inflammation, anti-oxidation, anti-diabetes, immunomodulation, attenuation of Alzheimer's disease risk factor, and anti-tumorigenic effects. Monascin and ankaflavin not only possess pleiotropic bioactivities, but are also more potent than monacolin K in lowering lipid levels and have lower toxicity. Monascin and ankaflavin act as the activators of PPARγ agonist/Nrf-2 that subsequently ameliorate metabolic syndrome. Following the intensive exploration of Monascus bioactivities in recent years, the focus of research on Monascus-functional foods has shifted from whole fermented products/extracts to specific bioactive compounds. Therefore, the production of monascin and ankaflavin is an important topic with respect to Monascus-functional foods. Although several genomic studies have paved the way for understanding the production of secondary metabolites in Monascus, efforts are still required to effectively manipulate the biosynthesis of secondary metabolites with genetic engineering and/or culture techniques.

γ-Aminobutyric Acid Imparts Partial Protection from Salt Stress Injury to Maize Seedlings by Improving Photosynthesis and Upregulating Osmoprotectants and Antioxidants

γ-Aminobutyric acid (GABA) has high physiological activity in plant stress physiology. This study showed that the application of exogenous GABA by root drenching to moderately (MS, 150 mM salt concentration) and severely salt-stressed (SS, 300 mM salt concentration) plants significantly increased endogenous GABA concentration and improved maize seedling growth but decreased glutamate decarboxylase (GAD) activity compared with non-treated ones. Exogenous GABA alleviated damage to membranes, increased in proline and soluble sugar content in leaves, and reduced water loss. After the application of GABA, maize seedling leaves suffered less oxidative damage in terms of superoxide anion (O₂^·-) and malondialdehyde (MDA) content. GABA-treated MS and SS maize seedlings showed increased enzymatic antioxidant activity compared with that of untreated controls, and GABA-treated MS maize seedlings had a greater increase in enzymatic antioxidant activity than SS maize seedlings. Salt stress severely damaged cell function and inhibited photosynthesis, especially in SS maize seedlings. Exogenous GABA application could reduce the accumulation of harmful substances, help maintain cell morphology, and improve the function of cells during salt stress. These effects could reduce the damage to the photosynthetic system from salt stress and improve photosynthesis and chlorophyll fluorescence parameters. GABA enhanced the salt tolerance of maize seedlings.