Diversity, Application, and Synthetic Biology of Industrially Important Aspergillus Fungi

Diversity within Aspergillus niger Clade and Description of a New Species: Aspergillus vinaceus sp. nov

Diversity of species within Aspergillus niger clade, currently represented by A. niger sensu stricto and A. welwitshiae, was investigated combining three-locus gene sequences, Random Amplified Polymorphic DNA, secondary metabolites profile and morphology. Firstly, approximately 700 accessions belonging to this clade were investigated using calmodulin gene sequences. Based on these sequences, eight haplotypes were clearly identified as A. niger (n = 247) and 17 as A. welwitschiae (n = 403). However, calmodulin sequences did not provide definitive species identities for six haplotypes. To elucidate the taxonomic position of these haplotypes, two other loci, part of the beta-tubulin gene and part of the RNA polymerase II gene, were sequenced and used to perform an analysis of Genealogical Concordance Phylogenetic Species Recognition. This analysis enabled the recognition of two new phylogenetic species. One of the new phylogenetic species showed morphological and chemical distinguishable features in comparison to the known species A. welwitschiae and A. niger. This species is illustrated and described as Aspergillus vinaceus sp. nov. In contrast to A. niger and A. welwitschiae, A. vinaceus strains produced asperazine, but none of them were found to produce ochratoxin A and/or fumonisins. Sclerotium production on laboratory media, which does not occur in strains of A. niger and A. welwitschiae, and strictly sclerotium-associated secondary metabolites (14-Epi-hydroxy-10,23-dihydro-24,25-dehydroaflavinine; 10,23-Dihydro-24,25-dehydroaflavinine; 10,23-Dihydro-24,25-dehydro-21-oxo-aflavinine) were found in A. vinaceus. The strain type of A. vinaceus sp. nov. is ITAL 47,456 (T) (=IBT 35556).

Degradation and Detoxification of Aflatoxin B1 by Tea-Derived Aspergillus niger RAF106

Microbial degradation is an effective and attractive method for eliminating aflatoxin B1 (AFB1), which is severely toxic to humans and animals. In this study, Aspergillus niger RAF106 could effectively degrade AFB1 when cultivated in Sabouraud dextrose broth (SDB) with contents of AFB1 ranging from 0.1 to 4 μg/mL. Treatment with yeast extract as a nitrogen source stimulated the degradation, but treatment with NaNO₃ and NaNO₂ as nitrogen sources and lactose and sucrose as carbon sources suppressed the degradation. Moreover, A. niger RAF106 still degraded AFB1 at initial pH values that ranged from 4 to 10 and at cultivation temperatures that ranged from 25 to 45 °C. In addition, intracellular enzymes or proteins with excellent thermotolerance were verified as being able to degrade AFB1 into metabolites with low or no mutagenicity. Furthermore, genomic sequence analysis indicated that the fungus was considered to be safe owing to the absence of virulence genes and the gene clusters for the synthesis of mycotoxins. These results indicate that A. niger RAF106 and its intracellular enzymes or proteins have a promising potential to be applied commercially in the processing and industry of food and feed to detoxify AFB1.

Rice-induced secondary metabolite gene expression in Aspergillus nidulans

Activation of silent biosynthetic gene clusters in fungi remains a challenge for discovery of new useful natural products. In this work, we identify a group of silent secondary metabolite gene clusters in Aspergillus nidulans that are induced by rice (Oryza sativa). Using reverse phase HPLC purification on extracts of rice, we identified the plant hormone gibberellic acid as one compound present in rice extracts that induced these silent genes. Additionally, select secondary metabolite (SM) genes activated by rice were tested for responses to several plant hormones which produced distinctly different transcriptomic profiles in A. nidulans. These observations support the idea that phytohormones play an important role in regulating fungal SM biosynthesis while additionally serving as a source of natural product chemical libraries to screen for useful compounds.

Physical Stress Induced Reduction of Proliferating Cells and Differentiated Neuroblasts Is Ameliorated by Fermented Laminaria japonica Extract Treatment

Laminaria japonica is widely cultivated in East Asia, including South Korea. Fucoidan, a main component of L. japonica, protects neurons from neurological disorders such as ischemia and traumatic brain injury. In the present study, we examined the effects of extract from fermented L. japonica on the reduction of proliferating cells and neuroblasts in mice that were physically (with electric food shock) or psychologically (with visual, auditory and olfactory sensation) stressed with the help of a communication box. Vehicle (distilled water) or fermented L. japonica extract (50 mg/kg) were orally administered to the mice once a day for 21 days. On the 19th day of the treatment, physical and psychological stress was induced by foot shock using a communication box and thereafter for three days. Plasma corticosterone levels were significantly increased after exposure to physical stress and decreased Ki67 positive proliferating cells and doublecortin immunoreactive neuroblasts. In addition, western blot analysis demonstrated that physical stress as well as psychological stress decreased the expression levels of brain-derived neurotrophic factor (BDNF) and the number of phosphorylated cAMP response element binding protein (pCREB) positive nuclei in the dentate gyrus. Fermentation of L. japonica extract significantly increased the contents of reduced sugar and phenolic compounds. Supplementation with fermented L. japonica extract significantly ameliorated the increases of plasma corticosterone revels and decline in the proliferating cells, neuroblasts, and expression of BDNF and pCREB in the physically stressed mice. These results indicate that fermented L. japonica extract has positive effects in ameliorating the physical stress induced reduction in neurogenesis by modulating BDNF and pCREB expression in the dentate gyrus.

The Conserved MAP Kinase MpkB Regulates Development and Sporulation without Affecting Aflatoxin Biosynthesis in Aspergillus flavus

In eukaryotes, the MAP kinase signaling pathway plays pivotal roles in regulating the expression of genes required for growth, development, and stress response. Here, we deleted the mpkB gene (AFLA_034170), an ortholog of the Saccharomyces cerevisiae FUS3 gene, to characterize its function in Aspergillus flavus, a cosmopolitan, pathogenic, and aflatoxin-producing fungus. Previous studies revealed that MpkB positively regulates sexual and asexual differentiation in Aspergillus nidulans. In A. flavus, mpkB deletion resulted in an approximately 60% reduction in conidia production compared to the wild type without mycelial growth defects. Moreover, the mutant produced immature and abnormal conidiophores exhibiting vesicular dome-immaturity in the conidiophore head, decreased phialide numbers, and very short stalks. Interestingly, the ΔmpkB mutant could not produce sclerotia but produced aflatoxin B1 normally. Taken together, these results suggest that the A. flavus MpkB MAP kinase positively regulates conidiation and sclerotia formation but is not involved in the production of secondary metabolites such as aflatoxin B1.

Dynamic changes in the metabolite profile and taste characteristics of Fu brick tea during the manufacturing process

Fu brick tea is a typical post-fermentation tea known for its special flavor and health benefits. Liquid chromatography-mass spectrometry, and sensory evaluation with multivariate analysis were used to characterize the dynamic changes in metabolite profile and taste characteristics. Seventy-one compounds were identified as critical metabolites, catechins, flavonoids, phenolic acids, terpenoids and others. During the manufacturing process, these compounds exhibited sharp fluctuations in content, the intensities of astringency, bitterness, and sourness of the tea materials reduced greatly, but the mellow intensity increased sharply. Several catechins and phenolic acids were positively related to the 'astringent', 'bitter', and 'sour' tastes attributes. The fungal genera, Aspergillus, Candida, unclassified_o_Hypocreales, unclassified_o_Saccharomycetales and Wallemia and the bacterial genus, Klebsiella, were identified as core functional microorganisms linked to the metabolic variations during the process. Overall, these findings provided a more comprehensive understanding of the formation of the sensory characteristics in Fu brick tea during the manufacturing process.

Genetic Manipulation and Transformation Methods for Aspergillus spp

Species of the genus Aspergillus have a variety of effects on humans and have been considered industrial cell factories due to their prominent ability for manufacturing several products such as heterologous proteins, secondary metabolites, and organic acids. Scientists are trying to improve fungal strains and re-design metabolic processes through advanced genetic manipulation techniques and gene delivery systems to enhance their industrial efficiency and utility. In this review, we describe the current status of the genetic manipulation techniques and transformation methods for species of the genus Aspergillus. The host strains, selective markers, and experimental materials required for the genetic manipulation and fungal transformation are described in detail. Furthermore, the advantages and disadvantages of these techniques are described.

Clustering analysis of large-scale phenotypic data in the model filamentous fungus Neurospora crassa

Background

With 9730 protein-coding genes and a nearly complete gene knockout strain collection, Neurospora crassa is a major model organism for filamentous fungi. Despite this abundance of information, the phenotypes of these gene knockout mutants have not been categorized to determine whether there are broad correlations between phenotype and any genetic features.

Results

Here, we analyze data for 10 different growth or developmental phenotypes that have been obtained for 1168 N. crassa knockout mutants. Of these mutants, 265 (23%) are in the normal range, while 903 (77%) possess at least one mutant phenotype. With the exception of unclassified functions, the distribution of functional categories for genes in the mutant dataset mirrors that of the N. crassa genome. In contrast, most genes do not possess a yeast ortholog, suggesting that our analysis will reveal functions that are not conserved in Saccharomyces cerevisiae. To leverage the phenotypic data to identify pathways, we used weighted Partitioning Around Medoids (PAM) approach with 40 clusters. We found that genes encoding metabolic, transmembrane and protein phosphorylation-related genes are concentrated in subsets of clusters. Results from K-Means clustering of transcriptomic datasets showed that most phenotypic clusters contain multiple expression profiles, suggesting that co-expression is not generally observed for genes with shared phenotypes. Analysis of yeast orthologs of genes that co-clustered in MAPK signaling cascades revealed potential networks of interacting proteins in N. crassa.

Conclusions

Our results demonstrate that clustering analysis of phenotypes is a promising tool for generating new hypotheses regarding involvement of genes in cellular pathways in N. crassa. Furthermore, information about gene clusters identified in N. crassa should be applicable to other filamentous fungi, including saprobes and pathogens.

Aspegillus terreus: From Soil to Industry and Back

Aspergillus terreus is an important saprophytic filamentous fungus that can be found in soils. Like many other soil microorganisms, A. terreus demonstrates multiple functions and offers various important metabolites, which can be used in different fields of human activity. The first application of A. terreus on an industrial level is the production of itaconic acid, which is now considered as one of the most important bioproducts in the Green Chemistry field. The general schemes for itaconic acid production have been studied, but in this mini-review some lines of future research are presented based on analysis of the published results. A. terreus is also intensively studied for its biocontrol activity and plant growth-promoting effect. However, this microorganism is also known to infect important crops such as, amongst others, rice, wheat, potato, sugar cane, maize, and soybean. It was suggested, however, that the balance between positive vs. negative effects is dependent on the soil-plant-inoculant dose system. A. terreus has frequently been described as an important human pathogen. Therefore, its safety manipulation in biotechnological processes for the production of itaconic acid and some drugs and its use in soil-plant systems should be carefully assessed. Some suggestions in this direction are discussed, particularly concerning the uses in crop production.

Assessment of the Microbiome and Potential Aflatoxin Associated With the Medicinal Herb Platycladus orientalis

Platycladi Semen, which is derived from the dried ripe seed of Platycladus orientalis, has been used for the treatment of insomnia and constipation in China for 2000 years. However, it is susceptible to fungal and aflatoxin contamination under proper humidity and temperature during storage. Although aflatoxin contamination in Platycladi Semen has been reported preliminarily, few studies have been conducted on fungal infection and aflatoxin contamination simultaneously. Thus, this work aims to provide an in-depth understanding of fungal contamination in Platycladi Semen, and information on aflatoxin contamination. We focused on a comparison of the difference in fungal diversity between aflatoxin-contaminated and aflatoxin-free Platycladi Semen samples. First, aflatoxin levels in 11 Platycladi Semen samples, which were collected from local herbal markets in Shandong, Anhui, and Hebei provinces throughout China, were determined by IAC-HPLC-FLD, and positive confirmation of detected samples was performed by LC-MS/MS. The samples were divided into two groups, based on production or non-production of aflatoxin. We then used the Illumina MiSeq PE250 platform, and targeted the internal transcribed spacer two sequences to analyze the diversity and composition of the fungal microbiome, as well as to assess the presence of potential mycotoxin-producing fungi. Results showed that five samples were contaminated with aflatoxins, one of which exceeded the legal limits of Chinese Pharmacopeia Commission (2015). At the phylum level, the Ascomycota was the most dominant in all tested samples, with a relative abundance of 83.04–99.46%. Aspergillus (27.88–97.28%), Xerochrysium (0–28.49%), and Xeromyces (0–22.24%) were the three predominant genera. Furthermore, differences in fungal composition between the aflatoxin-contaminated and aflatoxin-free groups, as well as between different provinces were observed. A total of 74 species were identified, and four potential mycotoxin-producing fungi were detected in all samples, namely Aspergillus flavus, Aspergillus fumigatus, Fusarium poae, and Penicillium steckii. In conclusion, we report the great diversity of fungi associated with Platycladi Semen, highlight the risk to consumers of ingesting potent aflatoxin, and provide a reference for the safe application and quality improvement of Platycladi Semen.

Tympanic membrane perforation secondary to Aspergillus niger otomycosis

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Aspergillus is a fungal mold, which is ubiquitous in nature.

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Aspergillosis results in significant morbidity and mortality worldwide.

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A rare case of tympanic membrane perforation secondary to Aspergillus niger otomycosis was reported.

Aspergillus niger is one of more than 340 different species belonging to the filamentous fungal genus Aspergillus. Aspergillosis can present with a wide range of clinical syndromes, and it results in significant morbidity and mortality worldwide. Here we described a rare case of the left central tympanic membrane perforation secondary to Aspergillus niger otomycosis. The patient underwent tympanoplasty with good improvement.

Developing Aspergillus niger as a cell factory for food enzyme production

Aspergillus niger has become one of the most important hosts for food enzyme production due to its unique food safety characteristics and excellent protein secretion systems. A series of food enzymes such as glucoamylase have been commercially produced by A. niger strains, making this species a suitable platform for the engineered of strains with improved enzyme production. However, difficulties in genetic manipulations and shortage of expression strategies limit the progress in this regard. Moreover, several mycotoxins have recently been detected in some A. niger strains, which raises the necessity for a regulatory approval process for food enzyme production. With robust strains, processing engineering strategies are also needed for producing the enzymes on a large scale, which is also challenging for A. niger, since its culture is aerobic, and non-Newtonian fluid properties are developed during submerged culture, making mixing and aeration very energy-intensive. In this article, the progress and challenges of developing A. niger for the production of food enzymes are reviewed, including its genetic manipulations, strategies for more efficient production of food enzymes, and elimination of mycotoxins for product safety.

Biofilm-Related, Time-Series Transcriptome and Genome Sequencing in Xylanase-Producing Aspergillus niger SJ1

In this study, we found that biofilm formation is a critical factor affecting the activity of Aspergillus niger SJ1 xylanase. Xylanase activity increased 8.8% from 1046.88 to 1147.74 U/mL during A. niger SJ1 immobilized fermentation with biofilm formation. Therefore, we carried out the work of genomic analysis and biofilm-related time-series transcriptome analysis of A. niger SJ1 for better understanding of the ability of A. niger SJ to produce xylanase and biofilm formation. Genome annotation results revealed a complete biofilm polysaccharide component synthesis pathway in A. niger SJ1 and five proteins regarding xylanase synthesis. In addition, results of transcriptome analysis revealed that the genes involved in the synthesis of cell wall polysaccharides and amino acid anabolism were highly expressed in the biofilm. Furthermore, the expression levels of major genes in the gluconeogenesis pathway and mitogen-activated protein kinase pathway were examined.

Integrated proteomics and metabolomics analysis of tea leaves fermented by Aspergillus niger, Aspergillus tamarii and Aspergillus fumigatus

Post-fermented Pu-erh tea (PFPT) is a microbially-fermented tea with distinct sensory qualities and multiple health benefits. Aspergillus are the dominant fungi in the fermentation and the main contributors to the characteristics of PFPT, so their underlying functions warrant detailed study. Here, tea leaves were fermented by Aspergillus niger, Aspergillus tamarii and Aspergillus fumigatus, and resulting samples (designated as Asn, Ast and Asf, respectively) were analyzed by proteomic and metabolomic methods. Changes to the composition of flavonoids, glycerophospholipids, organo-oxygen compounds and fatty acids resulting from Aspergillus fermentation were observed. Carbohydrate-active enzymes, e.g., endoglucanases and cellulases, for degradation of cellulose, starch, lignin, pectin, xylan and xyloglucan were identified. Glycoside hydrolase, glycosyltransferases, tannase, laccases, vanillyl-alcohol oxidases and benzoquinone reductase were identified and hypothesized to catalyze hydrolysis, oxidation, polymerization and degradation of phenolic compounds. Together, functions of Aspergillius were demonstrated as production of enzymes to change concentrations and compositions of metabolites in tea leaves.

Fungal Metabolite Asperaculane B Inhibits Malaria Infection and Transmission

Mosquito-transmitted Plasmodium parasites cause millions of people worldwide to suffer malaria every year. Drug-resistant Plasmodium parasites and insecticide-resistant mosquitoes make malaria hard to control. Thus, the next generation of antimalarial drugs that inhibit malaria infection and transmission are needed. We screened our Global Fungal Extract Library (GFEL) and obtained a candidate that completely inhibited Plasmodium falciparum transmission to Anopheles gambiae. The candidate fungal strain was determined as Aspergillus aculeatus. The bioactive compound was purified and identified as asperaculane B. The concentration of 50% inhibition on P. falciparum transmission (IC50) is 7.89 µM. Notably, asperaculane B also inhibited the development of asexual P. falciparum with IC50 of 3 µM, and it is nontoxic to human cells. Therefore, asperaculane B is a new dual-functional antimalarial lead that has the potential to treat malaria and block malaria transmission.

Quantitative Proteomics Analysis by Sequential Window Acquisition of All Theoretical Mass Spectra-Mass Spectrometry Reveals a Cross-Protection Mechanism for Monascus To Tolerate High-Concentration Ammonium Chloride

To achieve the accumulation of targeted secondary metabolites, microorganisms must adopt various protection mechanisms to avoid or reduce damage to cells caused by abiotic stresses, which formed from the changes of physical and chemical culture conditions. The protection mechanism of Monascus sp. to tolerate high-concentration ammonium chloride was analyzed by sequential window acquisition of all theoretical mass spectra-mass spectrometry proteomics in this work, and the results indicated that abiotic stresses caused by high-concentration ammonium chloride inhibited the synthesis of chitin and glycoprotein, leading to a decrease in cell wall integrity and, thus, affecting cell growth. At the same time, it also inhibited the complex enzyme III and IV activities of the mitochondrial cytochrome respiratory chain, leading to an increase in reactive oxygen species (ROS) levels. With the aim to respond to abiotic stresses, the cross-protection mechanism was implemented in Monascus, including self-protection of the Monascus cell by promoting synthesis of trehalose, a molecular chaperone that facilitates protein folding (such as heat-shock protein) and autophagy-related proteins, through not the enzyme protection system (superoxide dismutase, peroxidase, catalase, NADPH oxidase, and alternative oxidase) but the glutathione/glutaredoxin system, to maintain the intracellular redox state and then eliminate or reduce ROS damage to the cell. At the same time, an alternative respiratory pathway related to NADH dehydrogenase was activated to balance the material and energy metabolism.

Nidulantes of Aspergillus (Formerly Emericella): A Treasure Trove of Chemical Diversity and Biological Activities

The genus Emericella (Ascomycota) includes more than thirty species with worldwide distribution across many ecosystems. It is considered a rich source of diverse metabolites. The published classes of natural compounds that are discussed here are organized according to the following biosynthetic pathways: polyketides (azaphilones, cyclopentenone pigments, dicyanides, furan derivatives, phenolic ethers, and xanthones and anthraquinones); shikimate derivatives (bicoumarins); mevalonate derivatives (meroterpenes, sesquiterpenes, sesterterpenes and steroids) and amino acids derivatives (alkaloids (indole-derivatives, isoindolones, and piperazine) and peptides (depsipeptides)). These metabolites produce the wide array of biological effects associated with Emericella, including antioxidant, antiproliferative, antimalarial, antiviral, antibacterial, antioxidant, antihypertensive, anti-inflammatory, antifungal and kinase inhibitors. Careful and extensive study of the diversity and distribution of metabolites produced by the genus Emericella (either marine or terrestrial) revealed that, no matter the source of the fungus, the composition of the culture medium effectively controls the metabolites produced. The topic of this review is the diversity of metabolites that have been identified from Emericella, along with the contextual information on either their biological or geographic sources. This review presents 236 natural compounds, which were reported from marine and terrestrial Emericella. Amongst the reported compounds, only 70.2% were biologically assayed for their effects, including antimicrobial or cytotoxicity. This implies the need for substantial investigation of alternative activities. This review includes a full discussion of compound structures and disease management, based on materials published from 1982 through December 2019.

The role of the VosA-repressed dnjA gene in development and metabolism in Aspergillus species

The DnaJ family of proteins (or J-proteins) are molecular chaperones that govern protein folding, degradation, and translocation in many organisms. Although J-proteins play key roles in eukaryotic and prokaryotic biology, the role of J-proteins in Aspergillus species is currently unknown. In this study, we characterized the dnjA gene, which encodes a putative DnaJ protein, in two Aspergillus species: Aspergillus nidulans and Aspergillus flavus. Expression of the dnjA gene is inhibited by the velvet regulator VosA, which plays a pivotal role in spore survival and metabolism in Aspergillus. The deletion of dnjA decreased the number of asexual spores (conidia), produced abnormal conidiophores, and reduced sexual fruiting bodies (cleistothecia) or sclerotia. In addition, the absence of dnjA caused increased sterigmatocystin or aflatoxin production in A. nidulans and A. flavus, respectively. These results suggest that DnjA plays a conserved role in asexual and sexual development and mycotoxin production in Aspergillus species. However, DnjA also plays a species-specific role; AniDnjA but not AflDnjA, affects conidial viability, trehalose contents, and thermal tolerance of conidia. In plant virulence assay, the infection ability of the ΔAfldnjA mutant decreased in the kernels, suggesting that DnjA plays a crucial role in the pathogenicity of A. flavus. Taken together, these results demonstrate that DnjA is multifunctional in Aspergillus species; it is involved in diverse biological processes, including fungal differentiation and secondary metabolism.

Characterizing the role of Zn cluster family transcription factor ZcfA in governing development in two Aspergillus species

Filamentous fungi reproduce asexually or sexually, and the processes of asexual and sexual development are tightly regulated by a variety of transcription factors. In this study, we characterized a Zn2Cys6 transcription factor in two Aspergillus species, A. nidulans (AN5859) and A. flavus (AFLA_046870). AN5859 encodes a Zn2Cys6 transcription factor, called ZcfA. In A. nidulans, ΔzcfA mutants exhibit decreased fungal growth, a reduction in cleistothecia production, and increased asexual reproduction. Overexpression of zcfA results in increased conidial production, suggesting that ZcfA is required for proper asexual and sexual development in A. nidulans. In conidia, deletion of zcfA causes decreased trehalose levels and decreased spore viability but increased thermal sensitivity. In A. flavus, the deletion of the zcfA homolog AFLA_046870 causes increased conidial production but decreased sclerotia production; these effects are similar to those of zcfA deletion in A. nidulans development. Overall, these results demonstrate that ZcfA is essential for maintaining a balance between asexual and sexual development and that some roles of ZcfA are conserved in Aspergillus spp.

The Dose of Fungal Aerosol Inhaled by Workers in a Waste-Sorting Plant in Poland: A Case Study

Bioaerosol monitoring is a rapidly emerging area in the context of work environments because microbial pollution is a key element of indoor air pollution and plays an important role in certain infectious diseases and allergies. However, as yet, relatively little is known about inhaled doses of microorganisms in workplaces. Today, the important issue of social concern is due to waste management, transport, sorting, and processing of wastes and their environmental impact and effects on public health. In fact, waste management activities can have numerous adverse effects on human wellbeing. Health effects are generally linked to exposure (EX), defined as the concentration of a contaminant and the length of time a person is exposed to this concentration. Dose is an effective tool for evaluating the quantity of a contaminant that actually crosses the body’s boundaries and influences the goal tissue. This document presents an analysis of the fungal waste-sorting plant EX dose (FWSPED) inhaled by workers in a waste-sorting plant (WSP) in Poland in March 2019. The main purpose of this research was to assess FWSPED inhaled by workers in two cabins at the WSP: the preliminary manual sorting cabin (PSP) and the purification manual sorting cabin (quality control; QSP). It was found that the FWSPED inhaled by workers was 193 CFU/kg in the PSP and 185 CFU/kg in the QSP. Fungal particles were quantitatively evaluated and qualitatively identified by the GEN III Biolog system. During the research, it was found that isolates belonging to the Aspergilus flavus and Penicillum chrysogenum strains were detected most frequently in the WSP. The total elimination of many anthropogenic sources is not possible, but the important findings of this research can be used to develop realistic management policies and methods to improve the biological air quality of WSPs for effective protection of WSP workers.

Acetylsalicylic acid biosorption onto fungal-bacterial biofilm supported on activated carbons: an investigation via batch and fixed-bed experiments

This study reports on acetylsalicylic acid (ASA) biosorption onto fungal-bacterial biofilm supported on two types of activated carbons (one commercial type made of coconut fibers, CAC, and one other manufactured from fruit rinds of Hymenaea stigonocarpa Mart., HYAC, which after biofilm inoculation, they were named CAC-b and HYAC-b), via batch and fixed-bed experiments. These materials were characterized by BET Specific Surface Area and Scanning Electronic Microscopy (SEM). Biosorption onto HYAC-b was 57.2% higher than HYAC. Despite presenting the highest biosorption capacity over time (q_t = 85.4 ± 0.82 mg g^-1), CAC-b had a lower increase in efficiency (32.4%) compared to CAC. Kinetic data from the biosorption experiments responded well to the pseudo-first-order model thus suggests the predominance of physisorption, while without biofilm presence, there was a better agreement with the pseudo-second-order model, suggesting chemisorption. The possible interaction mechanism of ASA to biofilm was attributed to ionic forces between the drug in anionic form and eventual presence of cationic by-products of the biologically active surface metabolism. Biosorption equilibrium data responded better to the Sips model and CAC-b presented the highest biosorption capacity (q_e = 292.4 ± 2.01 mg g^-1). A combination of faster volumetric flow rates, higher inlet concentrations and shorter beds accelerated the breakthrough time of ASA biosorption in the fixed-bed experiments. These operational conditions affected C/C_o ratio in the following magnitude order: volumetric flow rate < inlet concentration < bed height. Breakthrough data responded better to the modified dose-response model compared to Thomas and Yoon-Nelson models.

Promotion of Metabolite Synthesis in Isaria cicadae, a Dominant Species in the Cicada Flower Microbiota, by Cicada Pupae

Cicada flowers, which are edible and medicinal mushrooms, are the fruiting bodies of Isaria cicadae, a fungus that is parasitic on the larvae of cicada pupae. We hypothesize that host factors might possess stimulatory activity on metabolite synthesis in Isaria cicadae. Here, we first compared the microbial community structures of different wild cicada flowers across geographical regions, compartments, and growth stages via high-throughput sequencing. Isaria cicadae TZC-3, an isolate of the most abundant operational taxonomic unit (OTU6782) in all the fungal communities, was isolated from wild cicada flowers. Furthermore, the effects of cicada pupae on metabolite synthesis in Isaria cicadae TZC-3 were studied in submerged culture. The contents of intercellular polysaccharides, adenosine, N6-(2-hydroxyethyl)-adenosine, free amino acids, and hydrolyzed monosaccharides in the mycelia cultured with cicada pupa powder (4%) were significantly increased as compared with the contents in the control group. This indicates that a cicada pupa can act as an elicitor for metabolite synthesis in Isaria cicadae.

Biomass-Derived Production of Itaconic Acid as a Building Block in Specialty Polymers

Biomass, the only source of renewable organic carbon on Earth, offers an efficient substrate for bio-based organic acid production as an alternative to the leading petrochemical industry based on non-renewable resources. Itaconic acid (IA) is one of the most important organic acids that can be obtained from lignocellulose biomass. IA, a 5-C dicarboxylic acid, is a promising platform chemical with extensive applications; therefore, it is included in the top 12 building block chemicals by the US Department of Energy. Biotechnologically, IA production can take place through fermentation with fungi like Aspergillus terreus and Ustilago maydis strains or with metabolically engineered bacteria like Escherichia coli and Corynebacterium glutamicum. Bio-based IA represents a feasible substitute for petrochemically produced acrylic acid, paints, varnishes, biodegradable polymers, and other different organic compounds. IA and its derivatives, due to their trifunctional structure, support the synthesis of a wide range of innovative polymers through crosslinking, with applications in special hydrogels for water decontamination, targeted drug delivery (especially in cancer treatment), smart nanohydrogels in food applications, coatings, and elastomers. The present review summarizes the latest research regarding major IA production pathways, metabolic engineering procedures, and the synthesis and applications of novel polymeric materials.

Improvement of the quality of soy sauce by reducing enzyme activity in Aspergillus oryzae

How to effectively increase or decrease the ability of A. oryzae to produce enzymes was the key to improve the quality of soy sauce. However, multi-core property of A. oryzae resulted in genetic instability of the new strain. Here, A. oryzae 3.042-3 which can stably produce mononuclear spores was constructed based on A. oryzae 3.042. A. oryzae 3.042-3-c obtained by transformation of the fragment of cis-CreA into A. oryzae 3.042-3 exhibited genetic stability. The fragment containing the cis-acting and the promoter CreA from A. oryzae was connected to chromosome VII in A. oryzae 3.042-3-c. Compared with A. oryzae 3.042-3, the cellulase activity of A. oryzae 3.042-3-c was reduced by 50.5% and the pectinase activity was decreased by 10.0%. At the end of the soy sauce fermentation, the salt-free solid content of A. oryzae 3.042-3-c was higher 58.9% than that of A. oryzae 3.042-3. The kinds and contents of the flavor components of the soy sauce from the fermentation by A. oryzae 3.042-3-c were higher than those of the A. oryzae 3.042 and A. oryzae 3.042-3, especially in alcohols and esters. HEMF was only found in the soy sauce from A. oryzae 3.042-3-c. The results indicated that the new strain A. oryzae 3.042-3-c could improve the quality of soy sauce from the low-salt solid fermentation by decreasing enzyme activity of cellulase and pectinase.

Safety of the fungal workhorses of industrial biotechnology: update on the mycotoxin and secondary metabolite potential of Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei

This review presents an update on the current knowledge of the secondary metabolite potential of the major fungal species used in industrial biotechnology, i.e., Aspergillus niger, Aspergillus oryzae, and Trichoderma reesei. These species have a long history of safe use for enzyme production. Like most microorganisms that exist in a challenging environment in nature, these fungi can produce a large variety and number of secondary metabolites. Many of these compounds present several properties that make them attractive for different industrial and medical applications. A description of all known secondary metabolites produced by these species is presented here. Mycotoxins are a very limited group of secondary metabolites that can be produced by fungi and that pose health hazards in humans and other vertebrates when ingested in small amounts. Some mycotoxins are species-specific. Here, we present scientific basis for (1) the definition of mycotoxins including an update on their toxicity and (2) the clarity on misclassification of species and their mycotoxin potential reported in literature, e.g., A. oryzae has been wrongly reported as an aflatoxin producer, due to misclassification of Aspergillus flavus strains. It is therefore of paramount importance to accurately describe the mycotoxins that can potentially be produced by a fungal species that is to be used as a production organism and to ensure that production strains are not capable of producing mycotoxins during enzyme production. This review is intended as a reference paper for authorities, companies, and researchers dealing with secondary metabolite assessment, risk evaluation for food or feed enzyme production, or considerations on the use of these species as production hosts.

Duplications and losses of genes encoding known elements of the stress defence system of the Aspergilli contribute to the evolution of these filamentous fungi but do not directly influence their environmental stress tolerance

The contribution of stress protein duplication and deletion events to the evolution of the Aspergilli was studied. We performed a large-scale homology analysis of stress proteins and generated and analysed three stress defence system models based on Saccharomyces cerevisiae, Schizosaccharomyces pombe and Aspergillus nidulans. Although both yeast-based and A. nidulans-based models were suitable to trace evolutionary changes, the A. nidulans-based model performed better in mapping stress protein radiations. The strong Mantel correlation found between the positions of species in the phylogenetic tree on the one hand and either in the A. nidulans-based or S. cerevisiae-based models on the other hand demonstrated that stress protein expansions and reductions contributed significantly to the evolution of the Aspergilli. Interestingly, stress tolerance attributes correlated well with the number of orthologs only for a few stress proteins. Notable examples are Ftr1 iron permease and Fet3 ferro-O2-oxidoreductase, elements of the reductive iron assimilation pathway, in the S. cerevisiae-based model, as well as MpkC, a HogA-like mitogen activated protein kinase in the A. nidulans-based model. In the case of the iron assimilation proteins, the number of orthologs showed a positive correlation with H2O2-induced stress tolerance while the number of MpkC orthologs correlated positively with Congo Red induced cell wall stress, sorbitol induced osmotic stress and H2O2 induced oxidative stress tolerances. For most stress proteins, changes in the number of orthologs did not correlate well with any stress tolerance attributes. As a consequence, stress tolerance patterns of the studied Aspergilli did not correlate with either the sets of stress response proteins in general or with the phylogeny of the species studied. These observations suggest that stress protein duplication and deletion events significantly contributed to the evolution of stress tolerance attributes of Aspergilli. In contrast, there are other processes, which may counterbalance the effects of stress gene duplications or deletions including (i) alterations in the structures of stress proteins leading to changes in their biological activities, (ii) varying biosynthesis of stress proteins, (iii) rewiring stress response regulatory networks or even (iv) acquiring new stress response genes by horizontal gene transfer. All these multilevel changes are indispensable for the successful adaptation of filamentous fungi to altering environmental conditions, especially when these organisms are entering new ecological niches.

Oryzines A & B, Maleidride Congeners from Aspergillus oryzae and Their Putative Biosynthesis

Aspergillus oryzae is traditionally used in East Asia for the production of food and brewing. In addition, it has been developed into a suitable host for the heterologous expression of natural product biosynthetic genes and gene clusters, enabling the functional analysis of the encoded enzymes. A. oryzae shares a 99.5% genome homology with Aspergillus flavus, but their secondary metabolomes differ significantly and various compounds unique to A. oryzae have been reported. While using A. oryzae as a host for heterologous expression experiments we discovered two new metabolites in extracts of A. oryzae M-2-3 with an unusual maleidride backbone, which were named oryzine A and B. Their structures were elucidated by high resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR) analysis. Their structural relationships with known maleidrides implied involvement of a citrate synthase (CS) and a polyketide (PKS) or fatty acid synthase (FAS) in their biosynthesis. Analysis of the A. oryzae genome revealed a single putative biosynthetic gene cluster (BGC) consistent with the hypothetical biosynthesis of the oryzines. These findings increase knowledge of the chemical potential of A. oryzae and are the first attempt to link a novel product of this fungus with genomic data.

Safety evaluation of the food enzyme α-amylase from a genetically modified Aspergillus niger (strain NZYM-SB)

The food enzyme is an α‐amylase (4‐α‐d‐glucan glucanohydrolase; EC 3.2.1.1), produced with the genetically modified Aspergillus niger strain NZYM‐SB by Novozymes A/S. The food enzyme does not contain the production organism or its DNA; therefore, there is no safety concern for the environment. The α‐amylase is intended for use in starch processing, beverage alcohol (distilling) processes and baking processes. Residual amounts of total organic solids (TOS) are removed by distillation and by the purification steps applied during the production of glucose syrups (by > 99%). Consequently, dietary exposure was not calculated for these two uses. Based on the maximum use levels recommended for the baking processes and individual consumption data from the EFSA Comprehensive European Food Consumption Database, dietary exposure to the food enzyme–TOS was estimated to be up to 3.075 mg TOS/kg body weight per day in European populations. The food enzyme did not induce gene mutations in bacteria or micronuclei in human lymphocytes. Subchronic toxicity was assessed by means of a repeated‐dose 90‐day oral toxicity study in rodents. A no observed adverse effect level (NOAEL) was derived that, compared with the dietary exposure, resulted in a sufficiently high margin of exposure (MOE). Similarity of the amino acid sequence to those of known allergens was searched and two matches were found. The Panel considered that the risk of allergic sensitisation and elicitation reactions by dietary exposure cannot be excluded, but the likelihood is considered low. Based on the genetic modifications, the manufacturing process, the compositional and biochemical data, the findings in the toxicological and genotoxicity studies, as well as the estimated dietary exposure, the Panel concluded that this food enzyme does not give rise to safety concerns under the intended conditions of use.

In vitro immunostimulatory potential of fungal β-glucans in pacific red snapper (Lutjanus peru) cells

This study attempts to describe the immunostimulatory effects of three fungal glucans on innate immunity responses in an in vitro assays using Pacific red snapper leukocytes. First, the yield glucans obtained was higher in Aspergillus niger, follow by Aspergillus ochraceus and Alternaria botrytis (40, 20 and 10%, respectively). Structural characterization of these fungal glucans by proton nuclear magnetic resonance (NMR) indicated structures containing (1-6)-branched (1-3)-β-D-glucan. The immunostimulatory activity of fungal glucans were assessed in head-kidney leukocytes at 24 h using colorimetric assays and molecular gene expression. In addition, the response against bacterial infection using Aeromonas hydrophila was evaluated by flow cytometry with annexin V/propidium iodide. Leukocytes responded positively to fungal glucans where the viability was higher than 80%. Interestingly, A. niger β-glucans enhanced the phagocytic ability and capacity in head-kidney leukocytes. Immunological assays reveled an increased in nitric oxide production, myeloperoxidase, superoxide dismutase and catalase activities, in fish stimulated with A. niger β-glucans. Induction of cytokines (IL-1β, TNF-α, IL-6, IL-8 and IL-12) were more pronounced in A. niger β-glucans leukocytes stimulated compared to other group. Finally, flow cytometry assay showed that A. botrytis and A. niger β-glucans were able to inhibit apoptosis caused by Aeromonas hydrophila in the Pacific red snapper leukocytes indicating an immunostimulant potent response by fungi derived-glucans. These results strongly support the idea that fungal β-glucans can stimulate the immune mechanism in head-kidney leukocytes and that Aspergillus niger β-glucan possess immunostimulatory properties cell increasing viability, and reducing necrotic cell death caused by Aeromonas hydrophila.