Aspergillus ochraceus: Metabolites, Bioactivities, Biosynthesis, and Biotechnological Potential

Exploring the potential of Aspergillus wentii: secondary metabolites and biological properties

Fungi are of considerable importance due to their capacity to biosynthesize various secondary metabolites with bioactive properties that draw high attention in new drug discovery with beneficial uses for improving human well-being and life quality. Aspergillus genus members are widespread and cosmopolitan species with varying economic significance in the fields of industry, medicine, and agriculture. Its species are renowned for their biosynthesis of secondary metabolites, characterized by both potent biological activity and structural novelty, making them a substantial reservoir for the development of new pharmaceuticals. The current work aimed at focusing on one species of this genus, Aspergillus wentii Wehmer, including its reported secondary metabolites in the period from 1951 to November 2023. A total of 97 compounds, including nitro-compounds, terpenoids, anthraquinones, xanthones, benzamides, and glucans. A summary of their bioactivities, as well as their biosynthesis was highlighted. Additionally, the reported applications of this fungus and its enzymes have been discussed. This review offers a useful reference that can direct future research into this fungus and its active metabolites, as well as their possible pharmacological and biotechnological applications.

Multigene phylogeny, bioactive properties, enzymatic and dye decolorization potential of selected marine fungi from brown algae and sponges of Mauritius

Marine fungi represent an important proportion of the microbial diversity in the oceans. They are attractive candidates for biotechnological purposes and industrial applications. Despite an increasing interest in mycology, marine fungi associated with sponges and algae have been poorly studied in Mauritius. The objectives of this study were to: 1) use multigene phylogenetic analyses to identify isolated marine fungi; 2) determine the differences in the antimicrobial and antioxidant properties of the fungal extracts; and 3) assess their enzyme activities and dye decolorization potential. Five fungal isolates viz Aspergillus chevalieri, Aspergillus iizukae, Aspergillus ochraceus, Exserohilum rostratum and Biatriospora sp. were identified based on phylogenetic analyses. There was no significant difference in the antimicrobial properties of the liquid and solid media extracts unlike the antioxidant properties (p < 0.05). The solid media extract of Aspergillus chevalieri (F2-SF) had a minimum inhibitory concentration of 0.156 mg/ml against Staphylococcus aureus while Aspergillus ochraceus (F25-SF) had a minimum inhibitory concentration of 0.313 and 2.5 mg/ml against Enterococcus faecalis and Salmonella typhi. The solid media extract of Biatriospora sp. (F34-SF) had a minimum inhibitory concentration of 0.195 and 1.563 mg/ml against Bacillus cereus, Escherichia coli and Enterobacter cloacae. An IC50 of 78.92 ± 4.71 μg/ml in the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) scavenging assay, ferric reducing antioxidant power (FRAP) value of 11.17 ± 0.20 mM Fe2+/g dry weight extract (DWE) and total phenolic content 360.35 ± 10.31 mg GAE/g DWE was obtained with the solid media extract of Aspergillus chevalieri (F2-SF). Aspergillus ochraceus (F25-SF) and Biatriospora sp. (F34-SF) solid media extracts showed lower IC50 values in the DPPH assay and higher total phenolic content as compared to the liquid media extracts. Aspergillus chevalieri was a good producer of the enzymes DNAse and lipase and had maximum percentage dye decolorization of 79.40 ± 17.72% on Congo red. An enzymatic index ≥ 2 was found for the DNAse and lipase and the maximum percentage dye decolorization of 87.18 ± 3.80% was observed with Aspergillus ochraceus on Methylene blue. Regarding Biatriospora sp., it was a moderate producer of the three enzymes amylase, DNAse and protease and had a maximum dye decolorization potential of 56.29 ± 6.51% on Crystal violet. This study demonstrates that Mauritian marine fungi possess good bioactive properties, enzymatic and dye decolorization potentials, that can potentially be considered for use in pharmaceutical and industrial applications.

Antimicrobial Activity of Depsidones and Macrocyclic Peptides Isolated from Marine Sponge-Derived Fungus Aspergillus nidulans M256

Chemical study on marine sponge-derivated fungus Aspergillus nidulans resulted in the isolation of seven depsidones (1-7) and two macrocyclic peptides (8 and 9). Their chemical structures were elucidated by extensive analyses of HRESIMS and NMR spectral data, as well as comparison with the literature. Compound 1 was an undescribed depsidone. All compounds exhibited significant antimicrobial activity (MICs: 2-128 μg/mL) towards at least one of seven microbial strains, including Bacillus cereus, Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, and Candida albicans. Of these, chlorinated depsidones (1-3, and 5) displayed potential antimicrobial activity. Nidulin (2) possessed good activity against tested strains except for S. enterica with MIC values in range of 2-16 μg/mL. Interestingly, undescribed depsidone 1 was selectively bioactive on the Gram-positive bacteria (MICs: 2-4 μg/mL) and yeast (MIC: 8 μg/mL) but inactivity on the Gram-negative bacteria (MICs: >256 μg/mL). Macrocyclic peptides, 8 and 9, displayed modest activity against E. faecalis strain with MIC values of 32 and 128 μg/mL, respectively.

Fungal and mycotoxin contaminants in cannabis and hemp flowers: implications for consumer health and directions for further research

Medicinal and recreational uses of Cannabis sativa, commonly known as cannabis or hemp, has increased following its legalization in certain regions of the world. Cannabis and hemp plants interact with a community of microbes (i.e., the phytobiome), which can influence various aspects of the host plant. The fungal composition of the C. sativa phytobiome (i.e., mycobiome) currently consists of over 100 species of fungi, which includes phytopathogens, epiphytes, and endophytes, This mycobiome has often been understudied in research aimed at evaluating the safety of cannabis products for humans. Medical research has historically focused instead on substance use and medicinal uses of the plant. Because several components of the mycobiome are reported to produce toxic secondary metabolites (i.e., mycotoxins) that can potentially affect the health of humans and animals and initiate opportunistic infections in immunocompromised patients, there is a need to determine the potential health risks that these contaminants could pose for consumers. This review discusses the mycobiome of cannabis and hemp flowers with a focus on plant-infecting and toxigenic fungi that are most commonly found and are of potential concern (e.g., Aspergillus, Penicillium, Fusarium, and Mucor spp.). We review current regulations for molds and mycotoxins worldwide and review assessment methods including culture-based assays, liquid chromatography, immuno-based technologies, and emerging technologies for these contaminants. We also discuss approaches to reduce fungal contaminants on cannabis and hemp and identify future research needs for contaminant detection, data dissemination, and management approaches. These approaches are designed to yield safer products for all consumers.

Hemostatically Active Proteinase Produced by Aspergillus ochraceus: Key Specific Properties and Effect on Target Proteins

The effect of A. ochraceus proteinase on the proteins of the human hemostasis system, fibrin, fibrinogen, plasminogen, protein C, and factor X, was studied. These proteins are key targets for proteolytic enzymes in therapy and diagnosis of thromboembolic complications. It was shown that A. ochraceus proteinase efficiently cleaves fibrin and fibrinogen, but does not act precisely, since it cuts all three subunits of these proteins. The proteinase did not have an activating effect on the plasminogen, a precursor of plasminogen and plasmin. The proteinase of A. ochraceus was shown to be the first fungal proteinase with proven activating activity towards the human hemostasis system factors protein C and factor X. For protein C activation, A. ochraceus proteinase requires Ca2+ ions. The enzyme was found to be sensitive to thrombin inhibitors, but not to plasmin inhibitors. A proteolytic action profile of the scope of this proteinase as a proteinase with activating protein C, factor X, and plasmin-like activity was proposed.

Secondary Metabolites, Biological Activities, and Industrial and Biotechnological Importance of Aspergillus sydowii

Marine-derived fungi are renowned as a source of astonishingly significant and synthetically appealing metabolites that are proven as new lead chemicals for chemical, pharmaceutical, and agricultural fields. Aspergillus sydowii is a saprotrophic, ubiquitous, and halophilic fungus that is commonly found in different marine ecosystems. This fungus can cause aspergillosis in sea fan corals leading to sea fan mortality with subsequent changes in coral community structure. Interestingly, A. sydowi is a prolific source of distinct and structurally varied metabolites such as alkaloids, xanthones, terpenes, anthraquinones, sterols, diphenyl ethers, pyrones, cyclopentenones, and polyketides with a range of bioactivities. A. sydowii has capacity to produce various enzymes with marked industrial and biotechnological potential, including α-amylases, lipases, xylanases, cellulases, keratinases, and tannases. Also, this fungus has the capacity for bioremediation as well as the biocatalysis of various chemical reactions. The current work aimed at focusing on the bright side of this fungus. In this review, published studies on isolated metabolites from A. sydowii, including their structures, biological functions, and biosynthesis, as well as the biotechnological and industrial significance of this fungus, were highlighted. More than 245 compounds were described in the current review with 134 references published within the period from 1975 to June 2023.

Notoamide R: A Prominent Diketopiperazine Fermentation Metabolite amongst Others of Aspergillus ochraceus in the Absence of Ochratoxins

Ochratoxin A is historically the most notable secondary metabolite of Aspergillus ochraceus on account of its toxicity to animals and fish. Currently, over 150 compounds of diverse structure and biosynthesis is a challenge to predict the array for any particular isolate. A brief focus 30 years ago on the failure to produce ochratoxins in foods in Europe and the USA revealed consistent failures to produce ochratoxin A by isolates from some USA beans. Analysis for familiar or novel metabolites particularly focused on a compound for which mass and NMR analyses were inconclusive. Resort to ¹⁴C-labelled biosynthetic precursors, particularly phenylalanine, to search for any close alternative to ochratoxins, was combined with conventional shredded-wheat/shaken-flask fermentation. This yielded, for an extract, an autoradiograph of a preparative silica gel chromatogram, which was subsequently analysed for an excised fraction using spectroscopic methodologies. Circumstances then delayed progress for many years until the present collaboration revealed notoamide R. Meanwhile, pharmaceutical discovery around the turn of the millennium revealed stephacidins and notoamides, biosynthetically combining indole, isoprenyl and diketopiperazine components. Later, in Japan, notoamide R was added as a metabolite of an Aspergillus sp. isolated from a marine mussel, and the compound was recovered from 1800 Petri dish fermentations. Renewed attention to our former studies in England has since shown for the first time that notoamide R can be a prominent metabolite of A. ochraceus, sourced from a single shredded wheat flask culture with its structure confirmed by spectroscopic data, and in the absence of ochratoxins. Renewed attention to the archived autoradiographed chromatogram allowed further exploration, but in particular has stimulated a fundamental biosynthetic approach to considering influences redirecting intermediary metabolism to secondary metabolite accumulation.

Quorum Sensing-Mediated Lipid Oxidation Further Regulating the Environmental Adaptability of Aspergillus ochraceus

Quorum sensing (QS) is a cellular strategy of communication between intra- and inter-specific microorganisms, characterized by the release of quorum sensing molecules (QSMs) that achieve coordination to adaptation to the environment. In Aspergillus, lipids carry population density-mediated stresses, and their oxidative metabolite oxylipins act as signaling to transmit information inside cells to regulate fungal development in a synchronized way. In this study, we investigated the regulation of density-dependent lipid metabolism in the toxigenic fungi Aspergillus ochraceus by the oxidative lipid metabolomics in conjunction with transcriptomics. In addition to proven hydroxyoctadecadienoic acids (HODEs), prostaglandins (PGs) also appear to have the properties of QSM. As a class of signaling molecule, oxylipins regulate the fungal morphology, secondary metabolism, and host infection through the G protein signaling pathway. The results of combined omics lay a foundation for further verification of oxylipin function, which is expected to elucidate the complex adaptability mechanism in Aspergillus and realize fungal utilization and damage control.

Aspergillus nidulans—Natural Metabolites Powerhouse: Structures, Biosynthesis, Bioactivities, and Biotechnological Potential

Nowadays, finding out new natural scaffolds of microbial origin increases at a higher rate than in the past decades and represents an auspicious route for reinvigorating the pool of compounds entering pharmaceutical industries. Fungi serve as a depository of fascinating, structurally unique metabolites with considerable therapeutic significance. Aspergillus genus represents one of the most prolific genera of filamentous fungi. Aspergillus nidulans Winter G. is a well-known and plentiful source of bioactive metabolites with abundant structural diversity, including terpenoids, benzophenones, sterols, alkaloids, xanthones, and polyketides, many of which display various bioactivities, such as cytotoxicity, antioxidant, anti-inflammatory, antiviral, and antimicrobial activities. The current work is targeted to survey the reported literature on A. nidulans, particularly its metabolites, biosynthesis, and bioactivities, in addition to recent reports on its biotechnological potential. From 1953 till November 2022, relying on the stated data, 206 metabolites were listed, with more than 100 references.