Effect of light on growth, pigment production and culture morphology of Monascus purpureus in solid-state fermentation

Role of histone H3K4 methyltransferase in regulating Monascus pigments production by red light-coupled magnetic field

Light, magnetic field, and methylation affected the growth and secondary metabolism of fungi. The regulation effect of the three factors on the growth and Monascus pigments (MPs) synthesis of Monascus purpureus was investigated in this study. 5-azacytidine (5-AzaC), DNA methylation inhibitor, was used to treat M. purpureus (wild-type, WT). Twenty micromolar 5-AzaC significantly promoted the growth, development, and MPs yield. Moreover, 250 lux red light and red light coupled magnetic field (RLCMF) significantly promoted the biomass. For WT, red light, and RLCMF significantly promoted MPs yield. But compared with red light treatment, only 0.2 mT RLCMF promoted the alcohol-soluble MPs yield. For histone H3K4 methyltransferase complex subunit Ash2 gene knockout strain (ΔAsh2), only 0.2 mT RLCMF significantly promoted water-soluble MPs yield. Yet red light, 1.0 and 0.2 mT RLCMF significantly promoted alcohol-soluble MPs yield. This indicated that methylation affected the MPs biosynthesis. Red light and weaker MF had a synergistic effect on the growth and MPs synthesis of ΔAsh2. This result was further confirmed by the expression of related genes. Therefore, histone H3K4 methyltransferase was involved in the regulation of the growth, development, and MPs synthesis of M. purpureus by the RLCMF.

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

BACKGROUND

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

RESULTS

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

CONCLUSION

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

The potentials and challenges of using fermentation to improve the sensory quality of plant-based meat analogs

Despite the advancements made in improving the quality of plant-based meat substitutes, more work needs to be done to match the texture, appearance, and flavor of real meat. This review aims to cover the sensory quality constraints of plant-based meat analogs and provides fermentation as a sustainable approach to push these boundaries. Plant-based meat analogs have been observed to have weak and soft textural quality, poor mouth feel, an unstable color, and unpleasant and beany flavors in some cases, necessitating the search for efficient novel technologies. A wide range of microorganisms, including bacteria such as Lactobacillus acidophilus and Lactiplantibacillus plantarum, as well as fungi like Fusarium venenatum and Neurospora intermedia, have improved the product texture to mimic fibrous meat structures. Additionally, the chewiness and hardness of the resulting meat analogs have been further improved through the use of Bacillus subtilis. However, excessive fermentation may result in a decrease in the final product's firmness and produce a slimy texture. Similarly, several microbial metabolites can mimic the color and flavor of meat, with some concerns. It appears that fermentation is a promising approach to modulating the sensory profiles of plant-derived meat ingredients without adverse consequences. In addition, the technology of starter cultures can be optimized and introduced as a new strategy to enhance the organoleptic properties of plant-based meat while still meeting the needs of an expanding and sustainable economy.

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

AIMS

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

METHODS AND RESULTS

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

CONCLUSIONS

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

The colors of life: an interdisciplinary artist-in-residence project to research fungal pigments as a gateway to empathy and understanding of microbial life

Background

Biological pigmentation is one of the most intriguing traits of many fungi. It holds significance to scientists, as a sign of biochemical metabolism and organism-environment interaction, and to artists, as the source of natural colors that capture the beauty of the microbial world. Furthermore, the functional roles and aesthetic appeal of biological pigmentation may be a path to inspiring human empathy for microorganisms, which is key to understanding and preserving microbial biodiversity. A project focused on cross-species empathy was initiated and conducted as part of an artist-in-residence program in 2021. The aim of this residency is to bridge the current divide between science and art through interdisciplinary practice focused on fungi.

Results

The residency resulted in multiple products that are designed for artistic and scientific audiences with the central theme of biological pigmentation in fungi and other microorganisms. The first product is a video artwork that focuses on Aspergillus niger as a model organism that produces melanin pigment in a biosynthetic process similar to that of humans. The growth and morphology of this commonplace organism are displayed through video, photo, animation, and time-lapse footage, inviting the viewer to examine the likenesses and overlaps between humans and fungi. The second product is The Living Color Database, an online compendium of biological colors for scientists, artists, and designers. It links organisms across the tree of life, focusing on fungi, bacteria, and archaea, and the colors they express through biological pigmentation. Each pigment is represented in terms of its chemistry, its related biosynthesis, and its color expressions according to different indices: HEX, RGB, and Pantone. It is available at color.bio.

Conclusions

As fungal biotechnology continues to mature into new application areas, it is as important as ever that there is human empathy for these organisms to promote the preservation and appreciation of fungal biodiversity. The products presented here provide paths for artists, scientists, and designers to understand microorganisms through the lens of color, promoting interspecies empathy through research, teaching, and practice.

Cost-effective process for the production of Monascus pigments using potato pomace as carbon source by fed-batch submerged fermentation

Potato pomace, generated from starch-processing industry, was applied as a cost-effective resource for producing Monascus pigments via submerged fermentation. First, the pigment-production capacity of potato pomace and its hydrolysate was compared. The results indicated that potato pomace was superior to its hydrolysate when used for producing Monascus pigments. The red and yellow pigments produced in potato pomace medium reached 27.8 and 19.7 OD units/ml in 7 days, with the yield of total pigments at 1,187.5 OD units/g, respectively, increased by 127.9%, 19.4%, and 46.3% compared with the data obtained from hydrolysate. Meanwhile, the citrinin produced in potato pomace medium decreased by 22.6%. Afterward, potato pomace, without hydrolysis, was used as carbon source to obtain the optimal pigment production conditions. In the batch fermentation process, it was found that high amount of pomace inhibited the growth rate of mycelia and the productivity of pigments, and the fed-batch fermentation process could enhance the yield and productivity of pigments. With the same final amount of pomace (80 g/L), the maximal levels of total pigments and productivity obtained from fed-batch process reached 118.8 OD units/ml and 13.2 OD units/(ml·day), which presented an increase of 35.2% and 67.1% compared with the not fed-batch group, respectively. The results demonstrated that potato pomace was a cost-effective substrate for producing Monascus pigments in terms of pigment production capacity and productivity when fed-batch submerged fermentation was applied.

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

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

Biotechnological approaches for the production of natural colorants by Talaromyces/Penicillium: A review

There has been an increased interest in replacing synthetic colorants by colorants obtained from natural sources, especially microbial pigments. Monascus pigments have been used as natural colorings and food additives in Asia for centuries but have raised toxicity issues. Recently, Talaromyces/Penicillium species have been recognized as potential strains to produce natural pigments similar to those produced by Monascus species. To date, it has not been published a literature compilation about the research and development activity of Talaromyces/Penicillium pigments. Developing a new bioprocess requires several steps, from an initial concept to a practical and feasible application. Industrial applications of fungal pigments will depend on: (i) characterization of the molecules to assure a safe consumption, (ii) stability of the pigments to the processing conditions required by the products where they will be incorporated, (iii) optimizing process conditions to achieve high yields, iv) implementing an efficient product recovery and (v) scale-up of the bioprocess. The above aspects have been reviewed in detail to evaluate the feasibility of reaching a commercial scale of the pigments produced by Talaromyces/Penicillium. Finally, the biological activities of the pigments and their potential applications are discussed.

Evaluation of tyrosol and farnesol as inducer in pigment production by Monascus purpureus ATCC16365

This study focused on investigating the effect of exogenously applied two quorum sensing molecules (tyrosol and farnesol) on the synthesis of bioactive metabolites (pigments, lactic acid, ethanol, and citric acid) in Monascus purpureus ATCC16365. None of the tested concentrations (62.5, 125, 250, and 500 µl/L) of farnesol affected the synthesis of metabolites as well as cell growth. As with farnesol application, none of the tested concentrations (3.45, 6.9, 13.8, and 27.6 mg/L) of tyrosol caused a significant change in the synthesis of lactic acid and citric acid as well as cell growth. Conversely, all of the tested concentrations of tyrosol increased pigment synthesis but reduced ethanol synthesis, compared with the control. Maximum increases (3.16-, 2.68-, and 2.87-fold increase, respectively) in yellow, orange, and red pigment production were achieved, especially when 6.9-mg/L tyrosol was added to the culture on day 3. On the contrary, 6.9-mg/L tyrosol reduced the content of citrinin by approximately 51.5%. This is the first report on the effect of tyrosol and farnesol on the synthesis of Monascus metabolites. Due to potential properties, such as low price, nonhuman toxicity, promotion of pigment synthesis, and reduction in citrinin synthesis, tyrosol can be used as a novel inducer in the fermentative production of Monascus pigments.

Regulating the pro- and anti-oxidant capabilities of bimetallic nanozymes for the detection of Fe2+ and protection of Monascus pigments

The emerging properties of mimicking enzymes open up new horizons for nanomaterials. Regulating their enzyme-like activity and exploiting their applications are currently the hot topics for nanozymes. Among their activities, the pro-oxidant and antioxidant capabilities of nanozymes are important to determine their unique physiological functions. In this paper, we demonstrate that PtRu NPs exhibit multiple enzyme-like activities (e.g. peroxidase, oxidase, ferroxidase, catalase and SOD) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity. The PtRu bimetallic nanozymes therefore show pro-oxidant and anti-oxidant functions. It was found that the enzyme-like activities of PtRu NPs are highly dependent on the Pt/Ru molar ratio and show a similar trend in the order of activity: Pt₉₀Ru₁₀ > Pt₇₅Ru₂₅ > Pt > Pt₄₀Ru₆₀, indicating that proper alloying of Pt with Ru can enhance both pro- and anti-oxidant capabilities. By employing the ferroxidase-like activity and catalase-like activity, we verified the applications of PtRu nanozymes in the detection of Fe²⁺ ions, and tried for the first time to protect Monascus pigments (MPs) from hydrogen peroxide oxidation. These results not only provide an effective way to optimize the pro- and anti-oxidant capabilities of nanozymes, but also provide prospects for the applications of nanozymes in protecting biologically active natural products.

Light irradiation can regulate the growth characteristics and metabolites compositions of Rhodotorula mucilaginosa

Light is an important factor that can induce the growth of varieties of organisms including fungi and their secondary metabolites. The evolutions of biomass, carotenoids, lipid production, compositions and contents of fatty acid and amino acid in Rhodotorula mucilaginosa were investigated under different light irradiation conditions. The results indicated that irradiation with 1700 lx could promote the growth and glucose assimilation of R. mucilaginosa, compared to the dark control, while the trial with 3500 lx had certain inhibiting effects. The carotenoids concentrations and percentages of unsaturated fatty acid (USFA, C16:1 and C18:1) increased with the improvement of irradiation intensity. Conversely, the proportions of saturated fatty acids (C16:0, C18:0 and C20:0) were decreased. The relative contents of amino acid and total protein were reduced under illumination compared to dark control. Conclusively, irradiation could change the cell growth and metabolites of the pigmented fungus, which implied that there may be a photoinduced mode exists in R. mucilaginosa similar to that of Neurospora crassa, and it also could be applied to regulate the biosynthesis and production of valuable components such as carotenoids and USFA.

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.

Solid-liquid Interface Screening SystemーApplication to the Screening of Antibiotic and Cytotoxic Substance-producing Fungi

　A useful tool for the screening of fungi producing biologically active secondary metabolites such as antibiotics and cytotoxic substances has been developed. An agar plate-organic solvent interface cultivation (A/S-IFC) system, which comprised a hydrophobic organic solvent (upper phase) , a fungal mat (middle phase) and an agar plate (lower phase) , was constructed. The metabolite profiles were compared among the A/S-IFC, a traditional submerged cultivation (SmC) and an extractive liquid surface immobilization (Ext-LSI) system consisted of a hydrophobic solvent (upper phase) , a fungal cells-ballooned microspheres (middle phase) and a liquid medium (lower phase) , with high-performance liquid chromatography-photodiode array detector (HPLC-PDA) . In the A/S-IFC, many hydrophobic metabolites vastly different from those in the SmC were accumulated in the organic phase as with the Ext-LSI. For example, a valuable azaphilone, sclerotiorin, was remarkably produced into the organic phase in the A/S-IFC. The A/S-IFC was applied to the screening of antibiotic-producing fungi. As a result of paper disk method, it was found that 321 isolated among 811 strains produced antifungal metabolites (hit rate, 39.6%) . Furthermore, 8, 23, and 30 strains also produced cytotoxic metabolites against SKOV-3 (human ovary adenocarcinoma) , MESO-1 (human malignant pleural mesothelioma) , and Jurkat cells (immortalized human T lymphocyte) .

Influences of light on growth, reproduction and hypocrellin production by Shiraia sp. SUPER-H168

Light is a very important signal for fungi since it influences many different physiological responses. The effects of dark or light at different wavelengths on growth, reproduction and hypocrellins of Shiraia sp. SUPER-H168 were studied: dark, white, red, yellow, green, blue and purple. All incubations under different light conditions had significant stimulating effects on aerial hyphae and suppressing effects on hypocrellin biosynthesis compared with dark incubation. Under blue and purple light especially blue light, the colonies with profuse growth of aerial mycelium were formed. Hypocrellin production reached 13.73 mg per dish under dark condition, and decreased to 4.01 mg and 2.83 mg per dish under white and blue light, respectively. Light condition not only influenced hypocrellin production but also influenced the composition of hypocrellins. Four types of hyphae, namely surface, aerial, biofilm and penetrative hyphae, were observed by light microscopy and SEM. This study found that biofilm hyphae was so closely connected with production of secondary metabolites, and hypocrellins were only produced by biofilm hyphae. Light promoted sexual development and inhibited asexual reproduction, especially blue light strongly inhibited asexual development.

Optimization of submerged fermentation medium for citrinin-free monascin production by Monascus

Microbial fermentation of citrinin-free Monascus pigments is in favor in the development of food industry. This study investigated the influences of carbon source, nitrogen source, and mineral salts on the cell growth, monascin (MS), and citrinin (CT) production in Monascus M9. A culture medium composition was established for maximizing the production of citrinin-free MS in submerged culture, as follows: 50 g/L Japonica rice powder, 20 g/L NH₄NO₃, 3 g/L NaNO₃, 1.5 g/L KH₂PO₄, 1 g/L MgSO₄ · 7H₂O, 0.2 g/L MnSO₄. Under these conditions, no CT was detectable by high performance liquid chromatography. The yield of MS reached 14.11 mg/g, improving approximately 30% compared with before optimization.

The molecular mechanisms of Monascus purpureus M9 responses to blue light based on the transcriptome analysis

Light is an important environmental factor that regulates various physiological processes of fungi. To thoroughly study the responses of Monascus to blue light, transcriptome sequencing was performed on mRNAs isolated from samples of Monascus purpureus M9 cultured under three conditions: darkness (D); exposure to blue light for 15 min/d (B15); and exposure to blue light for 60 min/d over 8 days (B60). The number of differentially expressed genes between the three pairs of samples-B15 vs D, B60 vs B15, and B60 vs D-was 1167, 1172, and 220, respectively. KEGG analysis showed the genes involved in primary metabolism including carbon and nitrogen metabolism were downregulated by B15 light treatment, whereas B15 upregulated expression of genes involved with aromatic amino acid metabolism, which associated with development, and branched chain amino acid metabolism, and fatty acid degradation, which can produce the biosynthetic precursors of pigments. When exposed to B60 conditions, genes with roles in carbohydrate metabolism and protein synthesis were upregulated as part of a stress response to blue light. Based on this study, we propose a predicted light-stimulated signal transduction pathway in Monascus. Our work is the first comprehensive investigation concerning the mechanism of Monascus responses to blue light.

Effects of Light Intensity and Color on the Biomass, Extracellular Red Pigment, and Citrinin Production of Monascus ruber

Light is a crucial environmental signal for fungi. In this work, the effects of different light intensities and colors on biomass, Monascus pigments (MPs) and citrinin production of Monascus ruber M7 were investigated. We have demonstrated that low intensity of blue light (500 lx) decreased Monascus biomass, increased MPs accumulation via upregulation of MpigA, MpigB, and MpigJ genes expression, but had no significant influence on citrinin production. High intensity of blue light (1500 lx) decreased citrinin accumulation but had no significant influence on biomass and MPs production after 14 days cultivation. Low intensity of green light (500 lx) stimulated citrinin production via upregulation of pksCT, mrl1, mrl2, and ctnA genes expression. One putative red light photoreceptor and two putative green light photoreceptors were identified in M. ruber M7. These observations will not only guide the practical production of Monascus but also contribute to our understanding light effects on Monascus.

Light regulation of mycotoxin biosynthesis: new perspectives for food safety

Mycotoxins are secondary metabolites produced by toxigenic fungi contaminating foods and feeds in pre-, post-harvest and processing, and represent a great concern worldwide, both for the economic implications and for the health of the consumers. Many environmental conditions are involved in the regulation of mycotoxin biosynthesis. Among these, light represents one of the most important signals for fungi, influencing several physiological responses such as pigmentation, sexual development and asexual conidiation, primary and secondary metabolism, including mycotoxin biosynthesis. In this review we summarise some recent findings on the effect of specific light wavelength and intensity on mycotoxin biosynthesis in the main toxigenic fungal genera. We describe the molecular mechanism underlying light perception and its involvement in the regulation of secondary metabolism, focusing on VeA, global regulator in Aspergillus nidulans, and the White-Collar proteins, key components of light response in Neurospora crassa. Light of specific wavelength and intensity exerts different effects both on growth and on toxin production depending on the fungal genus. In Penicillium spp. red (627 nm) and blue wavelengths (455-470 nm) reduce ochratoxin A (OTA) biosynthesis by modulating the level of expression of the ochratoxin polyketide synthase. Furthermore a mutual regulation between citrinin and OTA production is reported in Penicillium toxigenic species. In Aspergillus spp. the effect of light treatment is strongly dependent on the species and culture conditions. Royal blue wavelength (455 nm) of high intensity (1,700 Lux) is capable of completely inhibit fungal growth and OTA production in Aspergillus stenyii and Penicillum verrucosum. In Fusarium spp. the effect of light exposure is less effective; mycotoxin-producing species, such as Fusarium verticillioides and Fusarium proliferatum, grow better under light conditions, and fumonisin production increased. This review provides a comprehensive picture on light regulation of mycotoxin biosynthesis and discusses possible new applications of this resource in food safety.

Sensibilidade de isolados de fungos entomopatogênicos às radiações solar, ultravioleta e à temperatura

RESUMO: Este trabalho teve por objetivo avaliar a sensibilidade de isolados dos fungos Metarhizium anisopliae (Metsch.) Sorok. e Beauveria bassiana (Bals). Vuill. ao efeito das radiações solar e ultravioleta e da temperatura. Conídios dos isolados foram expostos, por vários períodos, aos raios de um simulador solar em diversas irradiâncias e a uma lâmpada de raios ultravioleta germicida. Os conídios do isolado de M. anisopliae foram também expostos às temperaturas de 19,5; 24,2 e 31,0ºC, e os do isolado de B. bassiana a 19,4; 20,8 e 28,3ºC, e 18,7; 23,8 e 30,9ºC. Avaliou-se a germinação de conídios pelo teste de viabilidade. Os isolados dos fungos se mostraram bastantes sensíveis aos raios do simulador solar e aos raios ultravioleta. A germinação de ambos sofreu significativa redução a partir de 30 minutos de exposição à radiação do simulador solar. O efeito mais severo foi evidenciado pelo isolado de B. bassiana, com grande redução da germinação dos conídios em todas as irradiâncias testadas. A sensibilidade à radiação ultravioleta também foi grande, pois ocorreu acentuada redução da germinação dos conídios do isolado de M. anisopliae (38,2%) e de B. bassiana (65%) já aos 30 segundos de exposição. A temperatura afetou a viabilidade de ambos os fungos. Temperaturas entre 23,8 e 31ºC favoreceram a germinação dos conídios, enquanto temperaturas próximas de 20ºC dificultaram a germinação.

Exploration of industrially important pigments from soil fungi

The worldwide interest of the current era is to increase tendency towards the use of natural substances instead of synthetic ones. So, alternative and effective environment friendly sustainable technologies are highly needed. Due to a broad range of biological activities, fungi are considered as a significant source of pigments. Among the fungal species in the soil, the genera of Aspergillus, Fusarium, Penicillium, Paecilomyces, and Trichoderma are dominant. The pigments commonly produced by fungi belong to aromatic polyketide groups such as melanins, quinones, flavins, ankaflavin, anthraquinone, and naphthoquinone. The use of fungal pigments has benefits which comprise easy and fast growth in the cheap culture medium and different color shades being independent of weather conditions and would be useful in various industrial applications. In relation to the toxic effects of the synthetic dyes, the natural dyes are easily degradable since they cause no detrimental effects. Thus, the study of pigments produced by soil fungi has tremendous use in medical, textile coloring, food coloring, and cosmetics.

Influence of Light Intensity on Growth and Pigment Production by Monascus ruber in Submerged Fermentation

To reduce environmental problems caused by glycerine accumulation and to make the production of biodiesel more profitable, crude glycerin without treatment was used as substrate for obtaining higher value-added bioproducts. Monascus ruber is a filamentous fungus that produces pigments, particularly red ones, which are used for coloring foods (rice wine and meat products). The interest in developing pigments from natural sources is increasing due to the restriction of using synthetic dyes. The effects of temperature, pH, microorganism morphology, aeration, nitrogen source, and substrates have been studied in the cultivation of M. ruber. In this work, it was observed that light intensity is also an important factor that should be considered for understanding the metabolism of the fungus. In M. ruber cultivation, inhibition of growth and pigment production was observed in Petri dishes and blaffed flasks exposed to direct illumination. Growth and pigment production were higher in Petri dishes and flasks exposed to red light and in the absence of light. Radial growth rate of M. ruber in plates in darkness was 1.50 mm day(-1) and in plates exposed to direct illumination was 0.59 mm day(-1). Maximum production of red pigments (8.32 UA) and biomass (8.82 g L(-1)) were obtained in baffled flasks covered with red film and 7.17 UA of red pigments, and 7.40 g L(-1) of biomass was obtained in flasks incubated in darkness. Under conditions of 1248 lux of luminance, the maximum pigment production was 4.48 UA, with production of 6.94 g L(-1) of biomass, indicating that the fungus has photoreceptors which influence the physiological responses.

Melanin-templated rapid synthesis of silver nanostructures

Background

As a potent antimicrobial agent, silver nanostructures have been used in nanosensors and nanomaterial-based assays for the detection of food relevant analytes such as organic molecules, aroma, chemical contaminants, gases and food borne pathogens. In addition silver based nanocomposites act as an antimicrobial for food packaging materials. In this prospective, the food grade melanin pigment extracted from sponge associated actinobacterium Nocardiopsis alba MSA10 and melanin mediated synthesis of silver nanostructures were studied. Based on the present findings, antimicrobial nanostructures can be developed against food pathogens for food industrial applications.

Results

Briefly, the sponge associated actinobacterium N. alba MSA10 was screened and fermentation conditions were optimized for the production of melanin pigment. The Plackett-Burman design followed by a Box-Behnken design was developed to optimize the concentration of most significant factors for improved melanin yield. The antioxidant potential, reductive capabilities and physiochemical properties of Nocardiopsis melanin was characterized. The optimum production of melanin was attained with pH 7.5, temperature 35°C, salinity 2.5%, sucrose 25 g/L and tyrosine 12.5 g/L under submerged fermentation conditions. A highest melanin production of 3.4 mg/ml was reached with the optimization using Box-Behnken design. The purified melanin showed rapid reduction and stabilization of silver nanostructures. The melanin mediated process produced uniform and stable silver nanostructures with broad spectrum antimicrobial activity against food pathogens.

Conclusions

The melanin pigment produced by N. alba MSA10 can be used for environmentally benign synthesis of silver nanostructures and can be useful for food packaging materials. The characteristics of broad spectrum of activity against food pathogens of silver nanostructures gives an insight for their potential applicability in incorporation of food packaging materials and antimicrobials for stored fruits and foods.

Monascus secondary metabolites: production and biological activity

The genus Monascus, comprising nine species, can reproduce either vegetatively with filaments and conidia or sexually by the formation of ascospores. The most well-known species of genus Monascus, namely, M. purpureus, M. ruber and M. pilosus, are often used for rice fermentation to produce red yeast rice, a special product used either for food coloring or as a food supplement with positive effects on human health. The colored appearance (red, orange or yellow) of Monascus-fermented substrates is produced by a mixture of oligoketide pigments that are synthesized by a combination of polyketide and fatty acid synthases. The major pigments consist of pairs of yellow (ankaflavin and monascin), orange (rubropunctatin and monascorubrin) and red (rubropunctamine and monascorubramine) compounds; however, more than 20 other colored products have recently been isolated from fermented rice or culture media. In addition to pigments, a group of monacolin substances and the mycotoxin citrinin can be produced by Monascus. Various non-specific biological activities (antimicrobial, antitumor, immunomodulative and others) of these pigmented compounds are, at least partly, ascribed to their reaction with amino group-containing compounds, i.e. amino acids, proteins or nucleic acids. Monacolins, in the form of β-hydroxy acids, inhibit hydroxymethylglutaryl-coenzyme A reductase, a key enzyme in cholesterol biosynthesis in animals and humans.

Monascus pigments

Monascus pigments (MPs) as natural food colorants have been widely utilized in food industries in the world, especially in China and Japan. Moreover, MPs possess a range of biological activities, such as anti-mutagenic and anticancer properties, antimicrobial activities, potential anti-obesity activities, and so on. So, in the past two decades, more and more attention has been paid to MPs. Up to now, more than 50 MPs have been identified and studied. However, there have been some reviews about red fermented rice and the secondary metabolites produced by Monascus, but no monograph or review of MPs has been published. This review covers the categories and structures, biosynthetic pathway, production, properties, detection methods, functions, and molecular biology of MPs.

Water-soluble red pigments from Isaria farinosa and structural characterization of the main colored component

The present study describes the red pigment synthesized by the filamentous fungi Isaria farinosa under submerged culture conditions. The pigment production was optimal under the following conditions: pH 5, agitation speed 150 rpm, temperature 27 °C, incubation time 192 h, light source total darkness, sucrose and glucose as carbon source, yeast extract, meat peptone and monosodium glutamate at a fixed concentration of 3% as nitrogen source. The addition of 10 mM CaCl₂ to the culture medium increased the biomass and pigment production. Structural elucidation of the pigment using gas chromatography-mass spectrometry, Fourier transform infrared spectroscopy and ¹H nuclear magnetic resonance spectroscopy revealed that the red pigment contains an anthraquinone-related compound. In addition, the isolated pigment was water soluble, and was stable when exposed to salt solution (96.1% of stability after treatment with sodium chloride), acid (72.1% with citric acid), heat (86.2% at 60 °C), and sunlight (99.4%). These results are promising to further exploit the fungal culture of Isaria farinosa for producing the red pigment and, subsequently, to considerably increase its yield. The study has commercial importance in the production of Isaria farinosa pigment for industrial application after considerable toxicological examination.

NMR-based metabonomic analysis on effect of light on production of antioxidant phenolic compounds in submerged cultures of Inonotus obliquus

This study was designed to investigate the light effect on biosynthesis of antioxidant phenolic compounds by Inonotus obliquus grown in submerged cultures using (1)H NMR spectroscopy combining multivariate pattern recognition strategies. I. obliquus were exposed to a range of light conditions and resultant data were compared to those from field-grown sclerotia and the mycelia grown in daylight. Daylight illumination inhibited biosynthesis of davallialactone and phelligridins and other hispidin analogs. Continuous darkness enhanced the formation of phelligridins, davallialactone and inoscavins. Phelligridins and davallialactone also occurred in the mycelia grown in blue and red light with levels lower than those found in darkness. In addition, polyphenols synthesized under daylight conditions showed less potential antioxidant activity than those determined with other light regimes. These findings demonstrate that light regulates biosynthesis of polyphenols in I. obliquus and their subsequent antioxidant activities, and (1)H NMR-based metabolic profiling is a cost-effective approach for evaluating light effects on fungal metabolisms.