Production and chemical characterization of pigments in filamentous fungi

Modulation of Growth and Mycotoxigenic Potential of Pineapple Fruitlet Core Rot Pathogens during In Vitro Interactions

Pineapple Fruitlet Core Rot (FCR) is a fungal disease characterized by a multi-pathogen pathosystem. Recently, Fusarium proliferatum, Fusarium oxysporum, and Talaromyces stollii joined the set of FCR pathogens until then exclusively attributed to Fusarium ananatum. The particularity of FCR relies on the presence of healthy and diseased fruitlets within the same infructescence. The mycobiomes associated with these two types of tissues suggested that disease occurrence might be triggered by or linked to an ecological chemical communication-promoting pathogen(s) development within the fungal community. Interactions between the four recently identified pathogens were deciphered by in vitro pairwise co-culture bioassays. Both fungal growth and mycotoxin production patterns were monitored for 10 days. Results evidenced that Talaromyces stollii was the main fungal antagonist of Fusarium species, reducing by 22% the growth of Fusarium proliferatum. A collapse of beauvericin content was observed when FCR pathogens were cross-challenged while fumonisin concentrations were increased by up to 7-fold. Antagonism between Fusarium species and Talaromyces stollii was supported by the diffusion of a red pigmentation and droplets of red exudate at the mycelium surface. This study revealed that secondary metabolites could shape the fungal pathogenic community of a pineapple fruitlet and contribute to virulence promoting FCR establishment.

Unveiling the Bioprospecting Efficacy and Textile Dyeing of a Novel Endophytic Mycobial Red Pigment

Natural pigments are becoming increasingly popular owing of their reliability. Microbial pigments provide an alternative to natural colours. A total of 24 fungal cultures were collected from leaf bits of Senna auriculata, with one strain (FNG1) producing an extracellular red orange pigment. Nigrospora oryzae was confirmed by using physical criteria and molecular phylogenetic study by using ITS and β- tubulin analysis. In EtOAc, the crude red pigment was the most soluble. The TLC analysis was used to partly purify the natural pigment. The partially purified fungal pigment was used in successive bioprospecting studies. The antimicrobial activity of the partially purified sample was assessed against eight human pathogens, with Leucobacter AA7 showing the largest zone of inhibition (200-500 µg/mL). The compound's DPPH scavenging activity enhanced from 38.2 to 67.9%, with an IC50 value of 34.195 ± 2.33 µg/mL. Cancer cells were suppressed by partly pure fungal pigment, but non-cancerous HEK 293 cells were unaffected. The GC-MS analysis was used to characterize the molecule present in the partly purified pigment. In addition, the cotton textiles have the greatest staining capability for crude mycobial pigment, which dyes quickly and has a negative cytotoxicity.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-024-01211-y.

Unveiling the fungal color palette: pigment analysis of Fusarium solani species complex and Curvularia verruculosa clinical isolates

Fungal species in the Nectriaceae, such as Fusarium spp. (Hypocreales: Nectriaceae), are etiologic agents of hyalohyphomycosis capable of producing violaceous or yellowish pigments under certain conditions, while Curvularia spp. (Pleosporales: Pleosporaceae) are agents of phaeohyphomycosis and typically produce melanin in their cell walls. In nectriaceous and pleosporaceous fungi, these pigments are mainly constituted by polyketides (e.g., azaphilones, naphthoquinones, and hydroxyanthraquinones). Considering the importance of pigments synthesized by these genera, this work focused on the selective extraction of pigments produced by eight Fusarium solani species complex and one Curvularia verruculosa isolate recovered from dermatomycosis specimens, their separation, purification, and posterior chemical analysis. The pigments were characterized through spectral and acid-base analysis, and their maximum production time was determined. Moreover, spectral identification of isolates was carried out to approach the taxonomic specificity of pigment production. Herein we describe the isolation and characterization of three acidic pigments, yellowish and pinkish azaphilones (i.e., coaherin A and sclerotiorin), and a purplish xanthone, reported for the first time in the Nectriaceae and Pleosporaceae, which appear to be synthesized in a species-independent manner, in the case of fusaria.

Exploring colorant production by amazonian filamentous fungi: Stability and applications

The aim of this study was to investigate the production, stability and applicability of colorants produced by filamentous fungi isolated from soil samples from the Amazon. Initially, the isolates were evaluated in a screening for the production of colorants. The influences of cultivation and nutritional conditions on the production of colorants by fungal isolates were investigated. The colorants produced by selected fungal isolates were chemically characterized using the Liquid Chromatography-Mass Spectrometry technique. The antimicrobial and cytotoxic activities, stability evaluation and applicability of the colorants were investigated. As results, we observed that the isolates Penicillium sclerotiorum P3SO224, Clonostachys rosea P2SO329 and Penicillium gravinicasei P3SO332 stood out since they produced the most intense colorants. Compounds produced by Penicillium sclerotiorum P3SO224 and Clonostachys rosea P2SO329 were identified as sclerotiorin and penicillic acid. The colorant fraction (EtOAc) produced by these species has antimicrobial activity, stability at temperature and at different pHs, stability when exposure to light and UV, and when exposed to different concentrations of salts, as well as being nontoxic and having the ability to dye fabrics and be used as a pigment in creams and soap. Considering the results found in this study, it was concluded that fungi from the soil in the Amazon have the potential to produce colorants with applications in the textile and pharmaceutical industries.

Isolation and Identification of Pigment-Producing Endophytic Fungi from the Amazonian Species Fridericia chica

Pigments of fungal origin have aroused increasing interest in the food dye and cosmetic industries since the global demand for natural dyes has grown. Endophytic microorganisms are a source of bioactive compounds, and Amazonian plant species can harbor fungi with a wide range of biotechnological applications. Popularly known in Brazil as crajiru, Fridericia chica is a medicinal plant that produces a red pigment. In this study, a total of 121 fungi were isolated in potato dextrose agar from three plants. We identified nine pigment-producing endophytic fungi isolated from branches and leaves of F. chica. The isolates that showed pigment production in solid media were molecularly identified via multilocus analysis as Aspergillus welwitschiae, A. sydowii, Curvularia sp., Diaporthe cerradensis (two strains), Hypoxylon investiens, Neoscytalidium sp. (two strains) and Penicillium rubens. These isolates were subjected to submerged fermentation in two culture media to obtain metabolic extracts. The extracts obtained were analyzed in terms of their absorbance between 400 and 700 nm. The pigmented extract produced by H. investiens in medium containing yeast extract showed maximum absorbance in the red absorption range (UA700 = 0.550) and significant antioxidant and antimicrobial activity. This isolate can thus be considered a new source of extracellular pigment.

A reduction in temperature induces bioactive red pigment production in a psychrotolerant Penicillium sp. GEU_37 isolated from Himalayan soil

Filamentous fungi are being globally explored for the production of industrially important bioactive compounds including pigments. In the present study, a cold and pH tolerant fungus strain Penicillium sp (GEU_37), isolated from the soil of Indian Himalaya, is characterized for the production of natural pigments as influenced by varying temperature conditions. The fungal strain produces a higher sporulation, exudation, and red diffusible pigment in Potato Dextrose (PD) at 15 °C as compared to 25 °C. In PD broth, a yellow pigment was observed at 25 °C. While measuring the effect of temperature and pH on red pigment production by GEU_37, 15 °C and pH 5, respectively, were observed to be the optimum conditions. Similarly, the effect of exogenous carbon and nitrogen sources and mineral salts on pigment production by GEU_37 was assessed in PD broth. However, no significant enhancement in pigmentation was observed. Chloroform extracted pigment was separated using thin layer chromatography (TLC) and column chromatography. The two separated fractions i.e., fractions I and II with Rf values 0.82 and 0.73, exhibited maximum light absorption, λ_max, at 360 nm and 510 nm, respectively. Characterization of pigments using GC-MS showed the presence of the compounds such as phenol, 2,4-bis (1,1-dimethylethyl) and eicosene from fraction I and derivatives of coumarine, friedooleanan, and stigmasterole in fraction II. However, LC-MS analysis detected the presence of derivatives of compound carotenoids from fraction II as well as derivative of chromenone and hydroxyquinoline as major compounds from both the fractions along with other numerous important bioactive compounds. The production of such bioactive pigments under low temperature conditions suggest their strategic role in ecological resilience by the fungal strain and may have biotechnological applications.

Ascomycota as a source of natural colorants

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

Optimization, purification, and structure elucidation of Anthraquinone pigment derivative from Talaromyces purpureogenus as a novel promising antioxidant, anticancer, and kidney radio-imaging agentAnthraquinone pigment as a promising antioxidant, anticancer, and radio-imaging agent

This study aims to investigate the bioproduction and prospective biological applications of a natural red pigment from Talaromyces purpureogenus AUMC2603. Maximum pigment yield was achieved by a numerical optimization at pH 6, temperature 25°C, and an 18-day incubation period on Yeast Malt Broth (YMB) media. The crude pigment was separated and purified into two pigment fractions via solid-phase extraction and then characterized as anthraquinone (dominant) and herquinone by LC/MS and ¹HNMR analysis. The crude pigment extract and the two separated fractions displayed a potential antioxidant activity. Additionally, they showed a powerful anticancer activity towards cancer cell lines, MCF-7, HepG-2, and HCT116 with less cytotoxicity on normal cell lines, MCF12F and BJ-1T. The radioiodination efficiency of the radiosynthesized ^99mTc-anthraquinone pigment complex was also investigated and optimized, obtaining a radiochemical yield of 92.70% ± 0.89%. An in vivo biodistribution study of the ^99mTc-anthraquinone pigment complex demonstrated a high kidney uptake of 34% injected dose per gram of organ tissue 60min after intravenous injection, and the complex retention remained high up to 120min. The current study is the first bioassay report on the efficacy of a purified anthraquinone from T. purpureogenus as a potent agent for kidney radio-imaging that could be applied in kidney cancer diagnosis.

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

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

The secondary metabolites from Beauveria bassiana PQ2 inhibit the growth and spore germination of Gibberella moniliformis LIA

Fungal secondary metabolites with antimicrobial properties are used for biological pest control. Their production is influenced by several factors as environment, host, and culture conditions. In the present work, the secondary metabolites from fermented extracts of Beauveria bassiana PQ2 were tested as antifungal agents against Gibberella moniliformis LIA. The L18 (21 × 37) orthogonal array from Taguchi methodology was used to assess 8 parameters (pH, agitation, sucrose, yeast extract, KH2PO4, MgSO4, NH4NO3, and CaCl2) in B. bassiana PQ2 submerged fermentation. The ability of the fermented extracts to slow down the growth rate of G. moniliformis LIA was evaluated. The results from 18 trials were analyzed by Statistica 7 software by evaluating the signal-to-noise ratio (S/N) to find the lower-the-better condition. Optimal culture conditions were pH, 5; agitation, 250 rpm; sucrose, 37.5 g/L-1; yeast extract, 10 g/L-1; KH2PO4, 0.8 g/L-1; MgSO4, 1.2 g/L-1; NH4NO3, 0.1 g/L-1; and CaCl2, 0.4 g/L-1, being the agitation at the highest level the most significant factor. The optimal conditions were validated in a sparged bottle bioreactor resulting in a higher S/N value (12.48) compared to the estimate. The extract obtained has the capacity to inhibit the germination of G. moniliformis spores at 24 h. HPLC-ESI-MS2 allowed to identify the water-soluble red pigment as oosporein (m/z 304.9). The secondary metabolites from B. bassiana PQ2 are a suitable alternative to control the growth and sporulation of G. moniliformis.

Fungal quinones: diversity, producers, and applications of quinones from Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium

Quinones represent an important group of highly structurally diverse, mainly polyketide-derived secondary metabolites widely distributed among filamentous fungi. Many quinones have been reported to have important biological functions such as inhibition of bacteria or repression of the immune response in insects. Other quinones, such as ubiquinones are known to be essential molecules in cellular respiration, and many quinones are known to protect their producing organisms from exposure to sunlight. Most recently, quinones have also attracted a lot of industrial interest since their electron-donating and -accepting properties make them good candidates as electrolytes in redox flow batteries, like their often highly conjugated double bond systems make them attractive as pigments. On an industrial level, quinones are mainly synthesized from raw components in coal tar. However, the possibility of producing quinones by fungal cultivation has great prospects since fungi can often be grown in industrially scaled bioreactors, producing valuable metabolites on cheap substrates. In order to give a better overview of the secondary metabolite quinones produced by and shared between various fungi, mainly belonging to the genera Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium, this review categorizes quinones into families such as emodins, fumigatins, sorbicillinoids, yanuthones, and xanthomegnins, depending on structural similarities and information about the biosynthetic pathway from which they are derived, whenever applicable. The production of these quinone families is compared between the different genera, based on recently revised taxonomy. KEY POINTS: • Quinones represent an important group of secondary metabolites widely distributed in important fungal genera such as Aspergillus, Penicillium, Talaromyces, Fusarium, and Arthrinium. • Quinones are of industrial interest and can be used in pharmacology, as colorants and pigments, and as electrolytes in redox flow batteries. • Quinones are grouped into families and compared between genera according to the revised taxonomy.

Safety Evaluation of Fungal Pigments for Food Applications

Pigments play a major role in many industries. Natural colors are usually much safer when compared to synthetic colors and may even possess some medicinal benefits. Synthetic colors are economical and can easily be produced compared to natural colors. In addition, raw plant materials for natural colors are limited and season dependent. Microorganisms provide an alternative source for natural colors and, among them, fungi provide a wide range of natural colorants that could easily be produced cheaply and with high yield. Along with pigment, some microbial strains are also capable of producing a number of mycotoxins. The commercial use of microbial pigments relies on the safety of colorants. This review provides a toxicity evaluation of pigments from fungal origins for food application.

Characterization of a Biofilm Bioreactor Designed for the Single-Step Production of Aerial Conidia and Oosporein by Beauveria bassiana PQ2

Beauveria bassiana is an entomopathogenic fungus that is used for the biological control of different agricultural pest insects. B. bassiana is traditionally cultivated in submerged fermentation and solid-state fermentation systems to obtain secondary metabolites with antifungal activity and infective spores. This work presents the design and characterization of a new laboratory-scale biofilm bioreactor for the simultaneous production of oosporein and aerial conidia by B. bassiana PQ2. The reactor was built with materials available in a conventional laboratory. K_La was determined at different air flows (1.5–2.5 L/min) by two different methods in the liquid phase and in the exhaust gases. The obtained values showed that an air flow of 2.5 L/min is sufficient to ensure adequate aeration to produce aerial conidia and secondary metabolites by B. bassiana. Under the conditions studied, a concentration of 183 mg oosporein per liter and 1.24 × 10⁹ spores per gram of support was obtained at 168 h of culture. These results indicate that the biofilm bioreactor represents a viable alternative for the production of products for biological control from B. bassiana.

OVAT Analysis and Response Surface Methodology Based on Nutrient Sources for Optimization of Pigment Production in the Marine-Derived Fungus Talaromyces albobiverticillius 30548 Submerged Fermentation

Pigment production from filamentous fungi is gaining interest due to the diversity of fungal species, the variety of compounds synthesized, and the possibility of controlled massive productions. The Talaromyces species produce a large panel of metabolites, including Monascus-like azaphilone pigments, with potential use as natural colorants in industrial applications. Optimizing pigment production from fungal strains grown on different carbon and nitrogen sources, using statistical methods, is widespread nowadays. The present work is the first in an attempt to optimize pigments production in a culture of the marine-derived T. albobiverticillius 30548, under the influence of several nutrients sources. Nutrient combinations were screened through the one-variable-at-a-time (OVAT) analysis. Sucrose combined with yeast extract provided a maximum yield of orange pigments (OPY) and red pigments (RPY) (respectively, 1.39 g/L quinizarin equivalent and 2.44 g/L Red Yeast pigment equivalent), as well as higher dry biomass (DBW) (6.60 g/L). Significant medium components (yeast extract, K₂HPO₄ and MgSO₄·7H₂O) were also identified from one-variable-at-a-time (OVAT) analysis for pigment and biomass production. A five-level central composite design (CCD) and a response surface methodology (RSM) were applied to evaluate the optimal concentrations and interactive effects between selected nutrients. The experimental results were well fitted with the chosen statistical model. The predicted maximum response for OPY (1.43 g/L), RPY (2.59 g/L), and DBW (15.98 g/L) were obtained at 3 g/L yeast extract, 1 g/L K₂HPO₄, and 0.2 g/L MgSO₄·7H₂O. Such optimization is of great significance for the selection of key nutrients and their concentrations in order to increase the pigment production at a pilot or industrial scale.

Molecular Characterization of Fungal Pigments

The industrial application of pigments of biological origin has been gaining strength over time, which is mainly explained by the increased interest of the consumer for products with few synthetic additives. So, the search for biomolecules from natural origin has challenged food scientists and technologists to identify, develop efficient and less consuming strategies for extraction and characterization of biopigments. In this task, elucidation of molecular structure has become a fundamental requirement, since it is necessary to comply with compound regulatory submissions of industrial sectors such as food, pharmaceutical agrichemicals, and other new chemical entity registrations. Molecular elucidation consists of establishing the chemical structure of a molecule, which allows us to understand the interaction between the natural additive (colorant, flavor, antioxidant, etc) and its use (interaction with the rest of the mixture of compounds). Elucidation of molecular characteristics can be achieved through several techniques, the most common being infrared spectroscopy (IR), spectroscopy or ultraviolet-visible spectrophotometry (UV-VIS), nuclear-resonance spectroscopy (MAGNETIC MRI), and mass spectrometry. This review provides the details that aid for the molecular elucidation of pigments of fungal origin, for a viable and innocuous application of these biopigments by various industries.

Selection of entomopathogenic fungus Beauveria bassiana (Deuteromycotina: Hyphomycetes) for the biocontrol of Dendroctonus ponderosae (Coleoptera: Curculionidae, Scolytinae) in Western Canada

The mountain pine beetle, Dendroctonus ponderosae, has infested over ~16 Mha of pine forests in British Columbia killing >50% of mature lodgepole pine, Pinus contorta, trees in affected stands. At present, it is functionally an invasive species in Alberta, killing and reproducing in evolutionarily naïve populations of lodgepole pine (P. contorta), novel jack pine (P. banksiana), and their hybrids. The entomopathogenic fungus Beauveria bassiana has shown some potential as a biocontrol agent of several bark beetle species. In this study, nine isolates of B. bassiana were examined for insect virulence characteristics, including conidiation rate, pigmentation, and infection rate in laboratory-reared D. ponderosae, to assess for their potential as biocontrol agents. The strains were categorized into three phenotypic groups based on pigmentation, conidial density, and myceliation rate. Virulence screening utilizing insect-based agar medium (D. ponderosae and European honeybee Apis mellifera carcasses) revealed no difference in selection of fungal growth. However, infection studies on D. ponderosae and A. mellifera showed contrasting results. In vivo A. mellifera infection model revealed ~5% mortality, representing the natural death rate of the hive population, whereas laboratory-reared D. ponderosae showed 100% mortality and mycosis. The LT₅₀ (median lethal time 50) ranges from 2 to 5 ± 0.33 days, and LT₁₀₀ ranges from 4 to 6 ± 0.5 days. We discuss the selective advantages of the three phenotypic groups in terms of virulence, pigmentation, conidial abundance, and tolerance to abiotic factors like UV and host tree monoterpenes. These results can further provide insights into the development of several phenotypically diverse B. bassiana strains in controlling the spread of the invasive D. ponderosae in Western Canada. KEY POINTS: • Three B. bassiana morphotype groups have been demonstrated to kill D. ponderosae. • A range of effective lethal times (LT₅₀ and LT₁₀₀) was established against D. ponderosae. • Variable tolerance to UV light and pine monoterpenes were observed in B. bassiana.

Bioinformatic insights into the biochemical efficacy of a fungal metabolite: asperyellone

In silico multifunctional attributes of Asperyellone.

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

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

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.

Fungal Pigments and Their Prospects in Different Industries

The public's demand for natural, eco-friendly, and safe pigments is significantly increasing in the current era. Natural pigments, especially fungal pigments, are receiving more attention and seem to be in high demand worldwide. The immense advantages of fungal pigments over other natural or synthetic pigments have opened new avenues in the market for a wide range of applications in different industries. In addition to coloring properties, other beneficial attributes of fungal pigments, such as antimicrobial, anticancer, antioxidant, and cytotoxic activity, have expanded their use in different sectors. This review deals with the study of fungal pigments and their applications and sheds light on future prospects and challenges in the field of fungal pigments. Furthermore, the possible application of fungal pigments in the textile industry is also addressed.

Lecanicillium aphanocladii: snake venom phospholipases A2 and proteases as tools to prospect enzymatic inhibitors

Natural enzyme inhibitors have been widely described in literature because of its pharmacological and cosmetic applications. Fungi found in caves represent a promising source of bioactive substances that are still little explored scientifically. Thus, the present work evaluated the presence of enzymatic modulators in a filtrate obtained from the cultivation of the cave fungus Lecanicillium aphanocladii (Family: Cordycipitaceae). Snake venoms from Bothrops alternatus and Bothrops atrox were used as an enzymatic source for the induction of the phospholipase, proteolytic, thrombolytic, cytotoxic and coagulant activities. Compounds present in the fungal filtrate inhibited 50, 23·8, 26·6, 50·9 and 52·5% of the proteolytic, phospholipase, haemolytic, thrombolytic and coagulant activities respectively. The filtrate was not cytotoxic on erythrocytes, but induced partial dissolution of thrombi. Fungal enzyme inhibitors that have low or no toxicity and can be obtained on a large scale and at low cost are relevant in the medical-scientific context. Therefore, the inhibition of phospholipases A₂ and proteases observed in the present work highlights the potential of fungal metabolites for the development of drugs that can be used in the treatment of haemostasis and inflammation-related disorders. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, secondary metabolites synthesized by Lecanicillium aphanocladii, a fungus isolated from caves, demonstrated modulating action on proteases and phospholipases A₂ present in snake venoms of the Bothrops genus, widely used as tools for the study of pathophysiology processes related to haemostasis and inflammation. The results suggest the possibility of future applications for these metabolites in the development of pharmaceuticals of medical-scientific interest.

Terrestrial Microorganisms: Cell Factories of Bioactive Molecules with Skin Protecting Applications

It is well known that terrestrial environments host an immense microbial biodiversity. Exposed to different types of stress, such as UV radiation, temperature fluctuations, water availability and the inter- / intra-specific competition for resources, terrestrial microorganisms have been evolved to produce a large spectrum of bioactive molecules. Bacteria, archaea, protists, fungi and algae have shown a high potential of producing biomolecules for pharmaceutical or other industrial purposes as they combine a sustainable, relatively low-cost and fast-production process. Herein, we provide an overview of the different bioactive molecules produced by terrestrial microorganisms with skin protecting applications. The high content in polyphenolic and carotenoid compounds produced by several strains, as well as the presence of exopolysaccharides, melanins, indole and pyrrole derivatives, mycosporines, carboxylic acids and other molecules, are discussed in the context of their antioxidant, photo-protective and skin-whitening activity. Relevant biotechnological tools developed for the enhanced production of high added value natural products, as well as the protecting effect of some antioxidant, hydrolytic and degrading enzymes are also discussed. Furthermore, we describe classes of microbial compounds that are used or have the potential to be used as antimicrobials, moisturizers, biosurfactants, pigments, flavorings and fragrances.

Degradative properties of two newly isolated strains of the ascomycetes Fusarium oxysporum and Lecanicillium aphanocladii

Two ascomycete strains were isolated from creosote-contaminated railway sleeper wood. By using a polyphasic approach combining morpho-physiological observations of colonies with molecular tools, the strains were identified as Fusarium oxysporum Schltdl. (IBPPM 543, MUT 4558; GenBank accession no. MG593980) and Lecanicillium aphanocladii Zare & W. Gams (IBPPM 542, MUT 242; GenBank accession no. MG593981). Both strains degraded hazardous pollutants, including polycyclic aromatic hydrocarbons, anthraquinone-type dyes, and oil. Oil was better degraded by F. oxysporum, but the aromatic compounds were better degraded by L. aphanocladii. With both strains, the degradation products of anthracene, phenanthrene, and fluorene were 9,10-anthraquinone, 9,10-phenanthrenequinone, and 9-fluorenone, respectively. During pollutant degradation, F. oxysporum and L. aphanocladii produced an emulsifying compound(s). Both fungi produced extracellular Mn-peroxidases, enzymes possibly involved in the fungal degradation of the pollutants. This is the first report on the ability of L. aphanocladii to degrade four-ring PAHs, anthraquinone-type dyes, and oil, with the simultaneous production of an extracellular Mn-peroxidase.

Tandem mass spectrometry methods to accelerate the identification of phytotoxic metabolites produced by Streptomyces sp. 39 PL

Natural products isolated by microorganisms are interesting in the search for new compounds with several biological activities. However, low concentration and structural diversity make the isolation a time-consuming step. Tandem mass spectrometry is a well-established technology for the identification and characterization of target microbial natural products due to high sensitivity and selectivity of these experiments. We developed a method employing neutral loss experiments (LC-ESI-MS/MS) to identify luminacins in microbial crude extracts. The luminacins class exhibited conserved fragmentation pattern with loss at 172 Da relative to glycosides fragment and this loss was used in searching for compounds belonging to this class. Therefore, the crude extract produced by Streptomyces sp. 39 PL was analysed and five luminacins were isolated - one is a novel luminacin I at 466 Da.

Investigation of Filamentous Fungi Producing Safe, Functional Water-Soluble Pigments

The production of water-soluble pigments by fungal strains indigenous to South Korea was investigated to find those that are highly productive in submerged culture. Among 113 candidates, 34 strains that colored the inoculated potato dextrose agar medium were selected. They were cultured in potato dextrose broth and extracted with ethanol. The productivity, functionality (radical-scavenging activities), and color information (CIELAB values) of the pigment extracts were measured. Five species produced intense yellowish pigments, and two produced intense reddish pigments that ranked the highest in terms of absorbance units produced per day. The pigment extracts of Penicillium miczynskii, Sanghuangporus baumii, Trichoderma sp. 1, and Trichoderma afroharzianum exhibited high radical-scavenging activity. However, the S. baumii extract showed moderate toxicity in the acute toxicity test, which limits the industrial application of this pigment. In conclusion, P. miczynskii KUC1721, Trichoderma sp. 1 KUC1716, and T. afroharzianum KUC21213 were the best fungal candidates to be industrial producers of safe, functional water-soluble pigments.

Diversity and Characterization of Endophytic Fungi Isolated From the Tropical Mangrove Species, Rhizophora mucronata, and Identification of Potential Antagonists Against the Soil-Borne Fungus, Fusarium solani

Rhizophora mucronata is an important ecosystem entity of the Malaysian mangrove forest. Since the species grows in a harsh environment, any organism that is isolated from this species would be of huge interest due to its potential in having novel bioactive compounds. In the present work, we isolated, identified and characterized, a total of 78 fungal isolates harboring inside the leaf tissues of R. mucronata. Molecular identification using the nuclear ribosomal DNA internal transcribe spacer (ITS) sequences returned with high similarity matches to known sequences in the GenBank. Maximum likelihood analysis revealed the phylogenetic relationship of all isolates from this study. Most of the dominating fungal endophytes were from the genera Pestalotiopsis, followed by Alternaria and Cladosporium. Six isolates representing the genera Alternaria, Fusarium, Nigrospora, Pestalotiopsis, Phoma, and Xylaria, were further screened for their antagonism activities. Dual culture test assay revealed their inhibition percentages against the phytopathogenic fungus Fusarium solani between 45-66%, and 0.8-23% when using non-volatile test assay. Of the six isolates, only Fusarium lateritium and Xylaria sp. showed antibacterial activities against the pathogenic bacteria, Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus, with the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) ranging from 0.5 to 2 mg/mL. The DPPH radical scavenging assay recorded a high level of antioxidant activity in Xylaria sp., 3-fold above that of F. lateritium. We demonstrate for the first time, two members belonging to the endophytic fungal community in the tropical mangrove species that have potential use as antagonists and antibacterial agents for future biotechnological applications.

Pigment Production by the Edible Filamentous Fungus Neurospora Intermedia

The production of pigments by edible filamentous fungi is gaining attention as a result of the increased interest in natural sources with added functionality in the food, feed, cosmetic, pharmaceutical and textile industries. The filamentous fungus Neurospora intermedia, used for production of the Indonesian food “oncom”, is one potential source of pigments. The objective of the study was to evaluate the fungus’ pigment production. The joint effect from different factors (carbon and nitrogen source, ZnCl2, MgCl2 and MnCl2) on pigment production by N. intermedia is reported for the first time. The scale-up to 4.5 L bubble column bioreactors was also performed to investigate the effect of pH and aeration. Pigment production of the fungus was successfully manipulated by varying several factors. The results showed that the formation of pigments was strongly influenced by light, carbon, pH, the co-factor Zn2+ and first- to fourth-order interactions between factors. The highest pigmentation (1.19 ± 0.08 mg carotenoids/g dry weight biomass) was achieved in a bubble column reactor. This study provides important insights into pigmentation of this biotechnologically important fungus and lays a foundation for future utilizations of N. intermedia for pigment production.

Regulatory cascade and biological activity of Beauveria bassiana oosporein that limits bacterial growth after host death

The regulatory network and biological functions of the fungal secondary metabolite oosporein have remained obscure. Beauveria bassiana has evolved the ability to parasitize insects and outcompete microbial challengers for assimilation of host nutrients. A novel zinc finger transcription factor, BbSmr1 (B. bassiana secondary metabolite regulator 1), was identified in a screen for oosporein overproduction. Deletion of Bbsmr1 resulted in up-regulation of the oosporein biosynthetic gene cluster (OpS genes) and constitutive oosporein production. Oosporein production was abolished in double mutants of Bbsmr1 and a second transcription factor, OpS3, within the oosporein gene cluster (ΔBbsmr1ΔOpS3), indicating that BbSmr1 acts as a negative regulator of OpS3 expression. Real-time quantitative PCR and a GFP promoter fusion construct of OpS1, the oosporein polyketide synthase, indicated that OpS1 is expressed mainly in insect cadavers at 24-48 h after death. Bacterial colony analysis in B. bassiana-infected insect hosts revealed increasing counts until host death, with a dramatic decrease (∼90%) after death that correlated with oosporein production. In vitro studies verified the inhibitory activity of oosporein against bacteria derived from insect cadavers. These results suggest that oosporein acts as an antimicrobial compound to limit microbial competition on B. bassiana-killed hosts, allowing the fungus to maximally use host nutrients to grow and sporulate on infected cadavers.

Identification and characterization of the ergochrome gene cluster in the plant pathogenic fungus Claviceps purpurea

Background

Claviceps purpurea is a phytopathogenic fungus infecting a broad range of grasses including economically important cereal crop plants. The infection cycle ends with the formation of the typical purple-black pigmented sclerotia containing the toxic ergot alkaloids. Besides these ergot alkaloids little is known about the secondary metabolism of the fungus. Red anthraquinone derivatives and yellow xanthone dimers (ergochromes) have been isolated from sclerotia and described as ergot pigments, but the corresponding gene cluster has remained unknown. Fungal pigments gain increasing interest for example as environmentally friendly alternatives to existing dyes. Furthermore, several pigments show biological activities and may have some pharmaceutical value.

Results

This study identified the gene cluster responsible for the synthesis of the ergot pigments. Overexpression of the cluster-specific transcription factor led to activation of the gene cluster and to the production of several known ergot pigments. Knock out of the cluster key enzyme, a nonreducing polyketide synthase, clearly showed that this cluster is responsible for the production of red anthraquinones as well as yellow ergochromes. Furthermore, a tentative biosynthetic pathway for the ergot pigments is proposed. By changing the culture conditions, pigment production was activated in axenic culture so that high concentration of phosphate and low concentration of sucrose induced pigment syntheses.

Conclusions

This is the first functional analysis of a secondary metabolite gene cluster in the ergot fungus besides that for the classical ergot alkaloids. We demonstrated that this gene cluster is responsible for the typical purple-black color of the ergot sclerotia and showed that the red and yellow ergot pigments are products of the same biosynthetic pathway. Activation of the gene cluster in axenic culture opened up new possibilities for biotechnological applications like the dye production or the development of new pharmaceuticals.

Electronic supplementary material

The online version of this article (doi:10.1186/s40694-016-0020-z) contains supplementary material, which is available to authorized users.

Polyphasic Approach Including MALDI-TOF MS/MS Analysis for Identification and Characterisation of Fusarium verticillioides in Brazilian Corn Kernels

Fusarium verticillioides is considered one of the most important global sources of fumonisins contamination in food and feed. Corn is one of the main commodities produced in the Northeastern Region of Brazil. The present study investigated potential mycotoxigenic fungal strains belonging to the F. verticillioides species isolated from corn kernels in 3 different Regions of the Brazilian State of Pernambuco. A polyphasic approach including classical taxonomy, molecular biology, MALDI-TOF MS and MALDI-TOF MS/MS for the identification and characterisation of the F. verticillioides strains was used. Sixty F. verticillioides strains were isolated and successfully identified by classical morphology, proteomic profiles of MALDI-TOF MS, and by molecular biology using the species-specific primers VERT-1 and VERT-2. FUM1 gene was further detected for all the 60 F. verticillioides by using the primers VERTF-1 and VERTF-2 and through the amplification profiles of the ISSR regions using the primers (GTG)₅ and (GACA)₄. Results obtained from molecular analysis shown a low genetic variability among these isolates from the different geographical regions. All of the 60 F. verticillioides isolates assessed by MALDI-TOF MS/MS presented ion peaks with the molecular mass of the fumonisin B1 (721.83 g/mol) and B2 (705.83 g/mol).