Fungal Pigments Research Articles

A Brief Review on the Emerging Role of Bacterial Pigments: From Industrial Uses to Novel Therapeutic Applications

Pigments produced by microorganisms are in high demand due to their safe, non-toxic, and biodegradable characteristics in both industrial and pharmaceutical fields. Using bacteria for pigment production offers several advantages, such as a short life cycle and ease of genetic modification. Numerous studies have highlighted that soil bacteria significantly contribute to the production of coloured pigments as secondary metabolites. Bacterial pigments are well-known for their antimicrobial, antioxidant, and anticancer properties, offering new therapeutic opportunities for the development of novel drugs. However, compared to fungal pigments, most bacterial pigments are still in the research and development stage. Hence, efforts to intensify bacterial pigment production are essential to make them readily available on the market at a low cost for various applications. This review article sheds light on bacterial pigments and their various applications based on the data available in the literature.

Metabolic engineering of Saccharomyces cerevisiae for the biosynthesis of a fungal pigment from the phytopathogenic fungus Cladosporium phlei

BackgroundCladosporium phlei is a phytopathogenic fungus that produces a pigment called phleichrome. This fungal perylenequinone plays an important role in the production of a photosensitizer that is a necessary component of photodynamic therapy. We applied synthetic biology to produce phleichrome using Saccharomyces cerevisiae.ResultsThe gene Cppks1, which encodes a non-reducing polyketide synthase (NR-PKS) responsible for the biosynthesis of phleichrome in C. phlei, was cloned into a yeast episomal vector and used to transform S. cerevisiae. In addition, a gene encoding a phosphopantetheinyl transferase (PPTase) of Aspergillus nidulans was cloned into a yeast integrative vector and also introduced into S. cerevisiae for the enzymatic activation of the protein product of Cppks1. Co-transformed yeasts were screened on a leucine/uracil-deficient selective medium and the presence of both integrative as well as episomal recombinant plasmids in the yeast were confirmed by colony PCR. The episomal vector for Cppks1 expression was so dramatically unstable during cultivation that most cells lost their episomal vector rapidly in nonselective media. This loss was also observed to a less degree in selective media. This data strongly suggests that the presence of the Cppks1 gene exerts a significant detrimental effect on the growth of transformed yeast cells and that selection pressure is required to maintain the Cppks1-expressing vector. The co-transformants on the selective medium showed the distinctive changes in pigmentation after a period of prolonged cultivation at 20 °C and 25 °C, but not at 30 °C. Furthermore, thin layer chromatography (TLC) revealed the presence of a spot corresponding with the purified phleichrome in the extract from the cells of the co-transformants. Liquid chromatography (LC/MS/MS) verified that the newly expressed pigment was indeed phleichrome.ConclusionOur results indicate that metabolic engineering by multiple gene expression is possible and capable of producing fungal pigment phleichrome in S. cerevisiae. This result adds to our understanding of the characteristics of fungal PKS genes, which exhibit complex structures and diverse biological activities.

Six new polyphenolic metabolites isolated from the Suillus granulatus and their cytotoxicity against HepG2 cells.

Edible mushrooms are an important source of nutraceuticals and for the discovery of bioactive metabolites as pharmaceuticals. In this work, six new polyphenolic metabolites suillusol A-D (1-4), suillusinoic acid (5), ethyl suillusinoate (6), were isolated from the Suillus granulatus. The structures of new compounds were elucidated using high-resolution electrospray ionization mass spectroscopy, nuclear magnetic resonance data, and single-crystal X-ray diffraction analysis. As far as we know, compound 1 represents an unprecedented type of natural product and compound 3 represents a new type of polyphenol fungal pigment, which may be biosynthetically related to thelephoric acid. The cytotoxicity against HepG2 cells of the new compounds were also evaluated. Compound 2 demonstrate significant inhibitory activity against HepG2 cells with IC50 values of 10.85 μM, surpassing that of positive control cisplatin. Moreover, compound 1 and 3 also exhibited moderate cytotoxic activity with their IC50 values measured at 35.60 and 32.62 μM, respectively. Our results indicate that S. granulatus is a rich source of chemical constituents that may provide new lead compounds for the development of anticancer agents.

Bioproduction and characterization of melanin pigment produced by the fungal strain Gliocephalotrichum sp. DSGB2

Introduction and Aim: The biosynthetic method of naturally occurring pigment melanin production has become a predominant technique in recent years owing to its cost-effectiveness, low chemical usage, and reduced purification procedure. This study aimed to investigate the significant production, characterization, and biological applications of fungal melanin pigment. Materials and Methods: Melanin production in Gliocephalotrichum sp. DSGB2 strain was carried out by submerged fermentation in tyrosine broth and further purified by acidification and precipitation methods. The purified melanin was characterized by analytical methods such as ultraviolet-visible absorbance, TLC, FTIR spectroscopy, and LC-MS. The DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging analysis was performed to evaluate antioxidant properties of melanin. Results: Pigment was confirmed as melanin based on tyrosinase enzyme assay, UV-visible spectroscopy absorbance, TLC, FTIR, and LC-MS analysis. The biosynthesis of melanin was optimized by varying the culture conditions, and the highest yield was obtained under pH 6 at 30ºC. The strain produced about 3.82 gL-1 of melanin in 5 days under optimum conditions and exhibited antioxidant activity. Conclusion: The study provides new ideas into the biosynthesis of water-soluble melanin by the fungal strain Gliocephalotrichum sp. DSGB2 has broad potential applications as an efficient biomaterial in the biopolymer, pharmaceutical sectors, cosmetic, and environmental.

Efficient production and characterization of melanin from Thermothelomyces hinnuleus SP1, isolated from the coal mines of Chhattisgarh, India.

In the present study, fungi were isolated and screened from barren land in south-eastern Coalfields limited (SECL) in Chhattisgarh, India. Out of 14 isolated fungi, only three fungal isolates exhibited pigmentation in screening studies. The isolated fungal strain SP1 exhibited the highest pigmentation, which was further utilized for in vivo production, purification, and characterization of melanin pigment. The physical and chemical properties of the fungal pigment showed insolubility in organic solvents and water, solubility in alkali, precipitation in acid, and decolorization with oxidizing agents. The physiochemical characterization and analytical studies of the extracted pigment using ultraviolet-visible spectroscopy and Fourier transform infrared (FTIR) confirmed it as a melanin pigment. The melanin-producing fungus SP1 was identified as Thermothelomyces hinnuleus based on 18S-rRNA sequence analysis. Furthermore, to enhance melanin production, a response surface methodology (RSM) was employed, specifically utilizing the central composite design (CCD). This approach focused on selecting efficient growth as well as progressive yield parameters such as optimal temperature (34.4°C), pH (5.0), and trace element concentration (56.24 mg). By implementing the suggested optimal conditions, the production rate of melanin increased by 62%, resulting in a yield of 28.3 mg/100 mL, which is comparatively higher than the actual yield (17.48 ± 2.19 mg/100 mL). Thus, T. hinnuleus SP1 holds great promise as a newly isolated fungal strain that could be used for the industrial production of melanin.

The colorful fungi of the Chilean forests: Production, chemical characterization and possible applications of their pigments.

In Chile, as in the rest of the world, only a small fraction of the fungal diversity inhabiting the wide variety of its ecosystems is known. This diversity must hide an inestimable richness of species with interesting biotechnological potential, including fungal pigment producers. Recently, interest in filamentous fungi has increased significantly due to their importance as alternative sources of pigments and colorants that are environmentally and human health friendly. As a result, fungal pigments are gaining importance in various industrial applications, such as food, textiles, pharmaceuticals, cosmetics, etc. The increasing consumer demand for "green label" natural colorants requires the exploration of different ecosystems in search of new fungal species that are efficient producers of different pigment with a wide range of colors and ideally without the co-production of mycotoxins. However, advances are also needed in pigment production processes through fermentation, scale-up from laboratory to industrial scale, and final product formulation and marketing. In this respect, the journey is still full of challenges for scientists and entrepreneurs. This chapter describes studies on pigment-producing fungi collected in the forests of central-southern Chile. Aspects such as the exploration of potential candidates as sources of extracellular pigments, the optimization of pigment production by submerged fermentation, methods of pigment extraction and purification for subsequent chemical characterization, and formulation (by microencapsulation) for potential cosmetic applications are highlighted. This potential use is due to the outstanding bioactivity of most fungal pigments, making them interesting functional ingredients for many applications. Finally, the use of fungal pigments for textile and spalting applications is discussed.

Non-photochemical quenching may contribute to the dominance of the pale mat-forming lichen Cladonia stellaris over the sympatric melanic Cetraria islandica.

The mat-forming fruticose lichens Cladonia stellaris and Cetraria islandica frequently co-occur on soils in sun-exposed boreal, subarctic, and alpine ecosystems. While the dominant reindeer lichen Cladonia lacks a cortex but produces the light-reflecting pale pigment usnic acid on its surface, the common but patchier Cetraria has a firm cortex sealed by the light-absorbing pigment melanin. By measuring reflectance spectra, high-light tolerance, photosynthetic responses, and chlorophyll fluorescence in sympatric populations of these lichens differing in fungal pigments, we aimed to study how they cope with high light while hydrated. Specimens of the two species tolerated high light equally well but with different protective mechanisms. The mycobiont of the melanic species efficiently absorbed excess light, consistent with a lower need for its photobiont to protect itself by non-photochemical quenching (NPQ). By contrast, usnic acid screened light at 450-700nm by reflectance and absorbed shorter wavelengths. The ecorticate usnic species with less efficient fungal light screening exhibited a consistently lower light compensation point and higher CO2 uptake rates than the melanic lichen. In both species, steady state NPQ rapidly increased at increasing light with no signs of light saturation. To compensate for less internal shading causing light fluctuations with a larger amplitude, the usnic lichen photobiont adjusted to changing light by faster induction and faster relaxation of NPQ rapidly transforming excess excitation energy to less damaging heat. The high and flexible NPQ tracking fluctuations in solar radiation probably contributes to the strong dominance of the usnic mat-forming Cladonia in open lichen-dominated heaths.

Antioxidant and antimicrobial screening of an unidentified yellow pigmented marine-derived fungus

The exploration of fungal secondary metabolites has increased significantly since the first discovery of penicillin. In addition, pigment derived from marine fungi attracts plenty of attention due to its complex and unusual chemical structures, which have tremendous antioxidants and antimicrobial activities. Hence, our current work aimed to characterize the crude pigment extract of an unidentified fungus SUCCF0001 and its potential as an antioxidant and antimicrobial agent. The fungus was cultivated on two semi-solid media namely MEA and PDA for 14 days at 25 °C, and two different liquids media namely MEB and PDB for 14 days at 25 °C with agitation at 150 r.p.m. The semi-solid medium and the fungal mycelium from the broth culture were extracted with methanol, while the liquid medium using ethyl acetate. The crude extracts were characterized using TLC plates and then visualized using DPPH, vanillin-H2SO4, and FeCL3. The presence of carotenoid pigment was detected using TLC with β-carotene as a marker. Antioxidant bioassay was screened using the DPPH method; while antimicrobial activity bioassay was conducted using the paper disc method against Bacillus subtilis, Escherichia coli, Micrococcus luteus, Pseudomonas aeruginosa and Candida tropicalis. The results showed that only the PDB extract had radical scavenging activity (RSA) > 50% for antioxidant activity. On the other hand, antimicrobial bioassay showed that only MEB extract had antimicrobial activity against B. subtilis. TLC analysis indicated the presence of antioxidants, terpenoids and phenols in both PDB and MEB extract. However, the result of fungal pigment characterization using TLC concluded that the pigment was not a β-carotene.

A closed-loop circularity in wood sugar as a renewable carbon source for fungal pigment production and application of pigments in wood colouration

The main objective is to demonstrate closed-loop circularity in the production of fungal pigment from renewable wood sugar hydrolysate (WSH) and impregnation of colour pigment into wood. Talaromyces sp 43 M, isolated from a New Zealand vineyard, was identified as Talaromyces ruber (TR) using multi-gene phylogenetic analysis. A mild pretreatment followed by ball milling was used to prepare Pinus radiata pulp which was enzymatically hydrolysed to generate WSH. Malt 30 g/L or WSH 40 g/L were optimum carbon sources when supplemented with peptone 10 g/L and meat extract 1 g/L as optimum nitrogen sources giving maximum production of extracellular pigment. TR completely metabolizes multiple carbon sources as well as fermentation inhibitors to elicit pigment production. The CIELAB colour characteristics of the pigment vary as a response to carbon sources (malt vs WSH) and fermentation time. The fluorescent pigment produced in malt and WSH medium were efficiently impregnated into wooden blocks.

Application and stability of fungal pigments using jelly sweets as a food model system

SummaryNatural pigments have seen an increase in usage over the past decades due to their acclaimed safety and active biological properties. This is in line with the shift in consumer market preferences requiring a source replacement for synthetic colourants. Filamentous fungi are amongst the natural sources currently explored for pigment production. In this study, the heat, pH and UV light stability of fungal pigments produced by Penicillium multicolour (dark brown), P. canescens (green) and P. herquie (yellow). Talaromyces verruculosus (red) and Fusarium solani (orange) were evaluated. The antioxidant properties of the pigments as influenced by these conditions were ascertained using the 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) assay. The pigments were also applied in a jelly sweet formulation and incubated at ambient temperature for 4 weeks. It was demonstrated that the pigment extracts of P. multicolour and T. verruculosus were significantly affected by higher pH (7.0 and 9.0), where the decline in antioxidant activity was observed. As far as high temperature and UV light exposure are concerned, all the pigment extracts, with exception of P. herquie, maintained an antioxidant activity above 35%. On the other hand, the L*a*b* values showed no overall significant change for heat and UV light exposure with the exception of P. canescens across the four pH levels (3.0, 4.0, 7.0 and 9.0), where an increase in the ‐a (green index) coupled with a decline in brightness (L* index) and b* (blue index) was observed. Finally, there was no significant change in colour over the 4 weeks of incubation. In conclusion, fungal pigments are generally stable at normal storage conditions (ambient temperature and normal light) and can be suitably applied in jelly sweets.

Marine fungal pigments; from Lab to potential applications

Marine fungal pigments; from Lab to potential applications

Microscopic Raman study of fungal pigment using the genetically amenable rock inhabitant Knufia petricola as a model organism

Fungal pigments such as melanin and carotenoids are distinctive markers of animal and plant pathogenic fungi as well as their environmental relatives. These complex pigments play important roles in pathogenicity and stress tolerance while also being useful as biomarkers. Accordingly, it is important to be able to identify in situ the pigments in black fungi, a group of clinical and environmental importance. In this study, wild-type and genetically modified strains of Knufia petricola A95 and wild fungal cells attached to ancient rock were investigated for their spectroscopic and microscopic Raman features and morphological appearance. Knockout mutants of melanin synthesis genes pks1 (polyketide synthase), sdh1 (scytalone dehydratase), and both pks1 and the carotenoid synthesis gene phd1 (phytoene desaturase) were studied We applied two different Raman microscopes using two lasers, with 633 nm and 488 nm wavelengths. We analyzed and compared Raman spectra between the measured reference substances and the mutant and wild-type strains. In the wild strain WT:A95, the peaks close to melanin peals were found at 1353 cm−1 and 1611 cm−1. There are no characteristic melanin peaks at 1580–1600 cm−1 and around 1350 cm−1 at the spectrum of the Δpks1/Δphd1 mutant and the Δsdh1 mutant. The Δpks1 mutant spectrum has the peaks at the beta-carotene v2 C-C in-plane stretch at 1155 cm−1 and v3 C-CH3 deformation at 1005 cm−1. The peaks of carotenoids and melanin were found in all mutants and the wild strain, except the Δpks1/Δphd1 mutant. Raman spectra allow for discrimination between the various pigments. Hence, interactions between natural fungal melanin, as well as other protective pigments, and complex environmental matrices can be characterized on a range of spatial and temporal scales.

Optimization of the process parameters for dyeing silk fabric with a fungal pigment using RSM

This study explores the extraction and application of a sustainable dye derived from Talaromyces purpurogenus fungi for dyeing silk fabric. The fungal dye imparted a vibrant red shade to silk, offering a promising alternative to synthetic dyes. The dyeing process was optimized using the Box and Behnken Design of RSM software, focusing on dye pH, dyeing temperature, and dyeing time. Silk fabric was dyed using an HTHP dyeing machine, and its performance was assessed in terms of colour strength, percent absorption, light fastness, rubbing fastness, and washing fastness. SEM imaging and FT-IR spectroscopy were employed to investigate the interaction between the dye and silk fabric. The optimized dyeing process resulted in silk fabric with a satisfactory red shade, demonstrating favorable fastness ratings at pH 5. The optimal dyeing conditions included a dye pH of 5, dyeing temperature of 82 °C, and dyeing time of 55 minutes, with an optical density of 10 and MLR of 1:30. Silk fabric exhibited maximum dye absorption capacity at pH 5, while maintaining excellent washing and rubbing fastness properties. However, the light fastness of the dyed silk fabric was relatively poor. Microscopic examination revealed a rough surface texture. Overall, this study highlights the potential of T. purpurogenus fungal dye as a sustainable alternative for silk fabric dyeing, while emphasizing the importance of addressing challenges such as improving light fastness through surface treatment and further exploring dyeing techniques.

Inhibitory Effects of the Fungal Pigment Rubiginosin C on Hyphal and Biofilm Formation in Candida albicans and Candida auris.

The two fungal human pathogens, Candida auris and Candida albicans, possess a variety of virulence mechanisms. Among them are the formation of biofilms to protect yeast against harsh conditions through the development of (pseudo)hyphae whilst also facilitating the invasion of host tissues. In recent years, increased rates of antifungal resistance have been associated with C. albicans and C. auris, posing a significant challenge for the effective treatment of fungal infections. In the course of our ongoing search for novel anti-infectives, six selected azaphilones were tested for their cytotoxicity and antimicrobial effects as well as for their inhibitory activity against biofilm and hyphal formation. This study revealed that rubiginosin C, derived from stromata of the ascomycete Hypoxylon rubiginosum, effectively inhibited the formation of biofilms, pseudohyphae, and hyphae in both C. auris and C. albicans without lethal effects. Crystal violet staining assays were utilized to assess the inhibition of biofilm formation, while complementary microscopic techniques, such as confocal laser scanning microscopy, scanning electron microscopy, and optical microscopy, were used to investigate the underlying mechanisms. Rubiginosin C is one of the few substances known to effectively target both biofilm formation and the yeast-to-hyphae transition of C. albicans and C. auris within a concentration range not affecting host cells, making it a promising candidate for therapeutic intervention in the future.

Improvement of DOPA-Melanin Production by Aspergillus nidulans Using Eco-Friendly and Inexpensive Substrates.

Fungal pigments, including melanin, are recognized as promising materials for biomedical, environmental, and technological applications. In previous studies, we have demonstrated that the DOPA-melanin produced by the MEL1 mutant of Aspergillus nidulans exhibits antioxidant, anti-inflammatory, and antimicrobial activities without any cytotoxic or mutagenic effects, suggesting its potential use in pharmaceuticals. In order to increase the yield of this pigment and reduce the costs of its large-scale production, the present study aimed to evaluate agro-industrial by-products, sugarcane molasses, vinasse, and corn steep liquor as inexpensive substrates for fungal growth using experimental design methodology. According to the results obtained, the optimal composition of the culture medium was 0.81% (v/v) vinasse and 1.62% (w/v) glucose, which promoted a greater production of melanin (225.39 ± 4.52 mg g-1 of biomass), representing a 2.25-fold increase compared with the condition before optimization (100.32 mg.g-1 of biomass). Considering the amount of biomass obtained in the optimized condition, it was possible to obtain a total melanin production of 1 g L-1. Therefore, this formulation of a less complex and low-cost culture medium composition makes the large-scale process economically viable for future biotechnological applications of melanin produced by A. nidulans.

The hidden rainbow: the extensive biotechnological potential of Antarctic fungi pigments.

The Antarctic continent is an extreme environment recognized mainly by its subzero temperatures. Fungi are ubiquitous microorganisms that stand out even among Antarctic organisms, primarily due to secondary metabolites production with several biological activities. Pigments are examples of such metabolites, which mainly occur in response to hostile conditions. Various pigmented fungi have been isolated from the Antarctic continent, living in the soil, sedimentary rocks, snow, water, associated with lichens, mosses, rhizospheres, and zooplankton. Physicochemical extreme environments provide a suitable setup for microbial pigment production with unique characteristics. The biotechnological potential of extremophiles, combined with concerns over synthetic pigments, has led to a great interest in natural pigment alternatives. Besides biological activities provided by fungal pigments for surviving in extreme environments (e.g., photoprotection, antioxidant activity, and stress resistance), it may present an opportunity for biotechnological industries. This paper reviews the biotechnological potential of Antarctic fungal pigments, with a detailed discussion over the biological role of fungal pigments, potential industrial production of pigments from extremophilic fungi, pigments toxicity, current market perspective and published intellectual properties related to pigmented Antarctic fungi.

Determination of toxicity and radioprotective properties of bacterial and fungal eumelanin pigments

Purpose Determination of the protective property of melanin, an organic polymer class consisting of phenolic and/or indolic compounds isolated from bacteria and fungi, against fast neutron radiation. To show that these melanin samples, which also have antioxidant and metal chelating properties, can be used as an active ingredient for a drug to be developed against neutrons used in nuclear research and medicine. Materials and methods Bacterial and fungal media were prepared, and melanin pigments were produced and isolated. For molecular characterization of pigments, bacterial genomic DNA extraction, 16S rDNA gene amplification processes, and fungal genomic DNA extraction, ITS1, and ITS4 Gene Regions amplification were performed. The DEL assay was implemented to determine the genotoxicity properties of bacterial and fungal melanin pigments. Samples were prepared in a pad measuring 10 ml volume (60 × 15 mm) at a concentration of 0.2–1 microgram in 1% agarose gel for radiation-absorbed dose measurements. Absorption measurements were made using 241Am-Be fast neutron source and Canberra brand NP series BF3 gaseous detector to determine the neutron radiation absorption capacity of all samples. The results obtained to determine the absorption degrees of melanin samples were compared with paraffin and normal concrete, which are widely used in neutron radiation shielding studies. Results Melanin pigments were obtained using different bacteria and fungi strains. Afterwards, the fast neutron radiation absorption capacity of these purified pigments were determined. Compared to reference samples, these pigments were found to have slightly lower radiation absorbing ability. In addition to these experiments, cytotoxicity tests were carried out using the Yeast DEL assay technique to evaluate the potential for use of these organic pigments in fields such as medicine and pharmacology. According to the results obtained from the tests, it was determined that these melanin samples did not have any toxic effects. Conclusion It was determined that these melanin samples have the potential to be used as a radioprotective drug active substance to protect the tissues and cells of people exposed to neutron radiation after a nuclear accident or nuclear war. Giving a drug that will be developed by using these active ingredients before or after people are exposed to a radiation environment can provide great benefits.

Valorization of pineapple peel waste for fungal pigment production using Talaromyces albobiverticillius: Insights into antibacterial, antioxidant and textile dyeing properties

The present study explores natural pigments as sustainable alternatives to synthetic textile dyes. Due to their therapeutic applications and easy production, fungal pigments have gained attention. However, data on pigment production using solid-state fermentation and optimization is limited. Milk whey was used to grow Talaromyces sp., followed by an evaluation of pigment production in solid and liquid media. Pineapple peels were used as a cost-effective substrate for pigment production, and a one-factor-at-a-time approach was used to enhance pigment production. Pineapple peel-based media produced 0.523 ± 0.231 mg/g of pigment after eight days of incubation. The crude pigment had promising antibacterial and significant antioxidant properties. The extraction fungal pigment's possible use as an eco-friendly textile dye was assessed through fabric dyeing experiments with different mordants. This work contributes to the valorization of agricultural waste and provides insight into using fungal pigments as sustainable alternatives to synthetic textile dyes.

Photogrammetry of Ultrafast Excited-State Intramolecular Proton Transfer Pathways in the Fungal Pigment Draconin Red.

Proton transfer processes of organic molecules are key to charge transport and photoprotection in biological systems. Among them, excited-state intramolecular proton transfer (ESIPT) reactions are characterized by quick and efficient charge transfer within a molecule, resulting in ultrafast proton motions. The ESIPT-facilitated interconversion between two tautomers (PS and PA) comprising the tree fungal pigment Draconin Red in solution was investigated using a combination of targeted femtosecond transient absorption (fs-TA) and excited-state femtosecond stimulated Raman spectroscopy (ES-FSRS) measurements. Transient intensity (population and polarizability) and frequency (structural and cooling) dynamics of -COH rocking and -C=C, -C=O stretching modes following directed stimulation of each tautomer elucidate the excitation-dependent relaxation pathways, particularly the bidirectional ESIPT progression out of the Franck-Condon region to the lower-lying excited state, of the intrinsically heterogeneous chromophore in dichloromethane solvent. A characteristic overall excited-state PS-to-PA transition on the picosecond timescale leads to a unique "W"-shaped excited-state Raman intensity pattern due to dynamic resonance enhancement with the Raman pump-probe pulse pair. The ability to utilize quantum mechanics calculations in conjunction with steady-state electronic absorption and emission spectra to induce disparate excited-state populations in an inhomogeneous mixture of similar tautomers has broad implications for the modeling of potential energy surfaces and delineation of reaction mechanisms in naturally occurring chromophores. Such fundamental insights afforded by in-depth analysis of ultrafast spectroscopic datasets are also beneficial for future development of sustainable materials and optoelectronics.

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

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