Microbial citric acid has high economic importance and widely used in beverage, food, detergents, cosmetics and pharmaceutical industries. The filamentous fungus Aspergillus niger is a work horse and ...important cell factory in industry for the production of citric acid. Although in-depth literatures and reviews have been published to explain the biochemistry, biotechnology and genetic engineering study of citric acid production by Aspergillus niger separately but the present review compiled, all the aspects with upto date brief summary of the subject describing microorganisms, substrates and their pre-treatment, screening, fermentation techniques, metabolic engineering, biochemistry, product recovery and numerous biotechnological application of citric acid for simple understanding of microbial citric acid production. The availability of genome sequence of this organism has facilitated numerous studies in gene function, gene regulation, primary and secondary metabolism. An attempt has been also made to address the molecular mechanisms and application of recent advanced techniques such as CRISPR/Cas9 systems in enhancement of citric acid production.
Surface-modified sulfur nanoparticles (SNPs) of two different sizes were prepared via a modified liquid-phase precipitation method, using sodium polysulfide and ammonium polysulfide as starting ...material and polyethylene glycol-400 (PEG-400) as the surface stabilizing agent. Surface topology, size distribution, surface modification of SNPs with PEG-400, quantitative analysis for the presence of sulfur in nanoformulations, and thermal stability of SNPs were determined by atomic force microscopy (AFM), dynamic light scattering (DLS) plus high-resolution transmission electron microscopy (HR-TEM), fourier transform infrared (FT-IR) spectroscopy, energy dispersive X-ray (EDX) spectroscopy, and thermogravimetric analysis (TGA), respectively. A simultaneous study with micron-sized sulfur (S⁰) and SNPs was carried out to evaluate their fungicidal efficacy against Aspergillus niger and Fusarium oxysporum in terms of radial growth, sporulation, ultrastructural modifications, and phospholipid content of the fungal strains using a modified poisoned food technique, spore-germination slide bioassay, environmental scanning electron microscopy (ESEM), and spectrometry. SNPs expressed promising inhibitory effect on fungal growth and sporulation and also significantly reduced phospholipid content.
Manipulation of the fungal epigenome is hypothesized to be an effective method for accessing natural products from silent biosynthetic pathways. A library of epigenetic modifiers was tested using the ...fungus Aspergillus niger to determine the impact of small-molecule inhibitors on reversing the transcriptional suppression of biosynthetic genes involved in polyketide (PKS), non-ribosomal peptide (NRPS), and hybrid PKS-NRPS (HPN) production. Examination of expressed sequence tag libraries from A. niger demonstrated that >70% of its PKS-, NRPS-, and HPN-encoding gene clusters were transcriptionally suppressed under standard laboratory culture conditions. Using a chemical epigenetic methodology, we showed that treatment of A. niger with suberoylanilide hydroxamic acid and 5-azacytidine led to the transcriptional upregulation of many secondary-metabolite-encoding biosynthetic gene clusters. Chemical epigenetic modifiers exhibited positional biases for upregulating chromosomally distal gene clusters. In addition, a phylogenetic-based preference was noted in the upregulation of reducing clade I PKS gene clusters, while reducing clade IV PKS gene clusters were largely unaffected. Manipulating epigenetic features in fungi is a powerful method for accessing the products of silent biosynthetic pathways. Moreover, this approach can be readily incorporated into modern microbial screening operations.
Zearalenone (ZEN) is one of the most common mycotoxin contaminants in food. For food safety, an efficient and environmental-friendly approach to ZEN degradation is significant. In this study, an
...strain, FS10, was stimulated with 1.0 μg/mL ZEN for 24 h, repeating 5 times to obtain a stressed strain, Zearalenone-Stressed-FS10 (ZEN-S-FS10), with high degradation efficiency. The results show that the degradation rate of ZEN-S-FS10 to ZEN can be stabilized above 95%. Through metabolomics analysis of the metabolome difference of FS10 before and after ZEN stimulation, it was found that the change of metabolic profile may be the main reason for the increase in the degradation rate of ZEN. The optimization results of degradation conditions of ZEN-S-FS10 show that the degradation efficiency is the highest with a concentration of 10
CFU/mL and a period of 28 h. Finally, we analyzed the degradation products by UPLC-q-TOF, which shows that ZEN was degraded into two low-toxicity products: C
H
O
S (Zearalenone 4-sulfate) and C
H
O
((E)-Zearalenone). This provides a wide range of possibilities for the industrial application of this strain.
Tannase (E.C. 3.1.1.20) is hypothesized to be involved in the metabolism of gallates and gallic acid (GA) in pu-erh tea fermentation. In this work, we measured tannase in Aspergillus niger fermented ...tea leaves and confirmed the production of fungal tannase during pu-erh tea fermentation. A decrease in catechin and theaflavin gallates and a significant increase in GA content and the relative peak areas of ethyl gallate, procyanidin A2, procyanidin B2, procyanidin B3, catechin-catechin-catechin, epiafzelechin, and epicatechin-epiafzelechin variable importance in the projection (VIP) > 1.0, p < 0.05, and fold change (FC) > 1.5 were observed using high performance liquid chromatography (HPLC) and metabolomics analysis of tea leaves fermented or hydrolyzed by tannase. In vitro assays showed that hydrolysis by tannase or polymerization of catechins increased the antioxidant activity of tea leaves. In summary, we identified a metabolic pathway for gallates and their derivatives in tea leaves hydrolyzed by tannase as well as associated changes in gallate and GA concentrations caused by fungal tannase during pu-erh tea fermentation.
Second generation (2G) ethanol is produced by breaking down lignocellulosic biomass into fermentable sugars. In Brazil, sugarcane bagasse has been proposed as the lignocellulosic residue for this ...biofuel production. The enzymatic cocktails for the degradation of biomass-derived polysaccharides are mostly produced by fungi, such as Aspergillus niger and Trichoderma reesei. However, it is not yet fully understood how these microorganisms degrade plant biomass. In order to identify transcriptomic changes during steam-exploded bagasse (SEB) breakdown, we conducted a RNA-seq comparative transcriptome profiling of both fungi growing on SEB as carbon source.
Particular attention was focused on CAZymes, sugar transporters, transcription factors (TFs) and other proteins related to lignocellulose degradation. Although genes coding for the main enzymes involved in biomass deconstruction were expressed by both fungal strains since the beginning of the growth in SEB, significant differences were found in their expression profiles. The expression of these enzymes is mainly regulated at the transcription level, and A. niger and T. reesei also showed differences in TFs content and in their expression. Several sugar transporters that were induced in both fungal strains could be new players on biomass degradation besides their role in sugar uptake. Interestingly, our findings revealed that in both strains several genes that code for proteins of unknown function and pro-oxidant, antioxidant, and detoxification enzymes were induced during growth in SEB as carbon source, but their specific roles on lignocellulose degradation remain to be elucidated.
This is the first report of a time-course experiment monitoring the degradation of pretreated bagasse by two important fungi using the RNA-seq technology. It was possible to identify a set of genes that might be applied in several biotechnology fields. The data suggest that these two microorganisms employ different strategies for biomass breakdown. This knowledge can be exploited for the rational design of enzymatic cocktails and 2G ethanol production improvement.
This paper investigates Aspergillus niger's behaviour in the presence of mobile Al3+ species by evaluating the changes in oxalate exudation at various aluminium contents. When the fungus was exposed ...to Al3+, no significant changes in oxalate production were observed until 100 mg.L−1 aluminium was reached resulting in oxalate production decrease by 18.2%. By stripping the culture medium completely of phosphate, even more prominent decrease by 34.8% and 67.1% at 10 and 100 mg.L−1 aluminium was observed, respectively, indicating the phosphate's significance instead of Al3+ in oxalate production. Our results suggest that the low phosphate bioavailability, which most likely resulted from its interaction with Al3+, stimulated the overproduction of oxalate by A. niger. Furthermore, when the fungus was incubated in aluminium-free media supplemented with 0.1 mM of phosphate, oxalate production increased up to 281.5 μmol.g−1, while at 1.85 mM of available phosphate only 80.7 μmol.g−1 of oxalate was produced. This indicates that oxalic acid is produced by fungus not as a mean to detoxify aluminium, but as an attempt to gain access to additional phosphate.
Mobile Al3+ decreases phosphate's bioavailability due to AlPO4 formation, inducing increased exudation of oxalate by Aspergillus niger in response. Therefore, fungal ability to produce oxalate is driven by phosphate's availability and not because of aluminium's toxicity. Chelation of Al3+ is utilized by fungus in attempt to increase availability of phosphate. Display omitted
•Presence of Al3+ species didn't induce overproduction of oxalate by Aspergillus niger.•Increased oxalate production was driven by available phosphate instead of aluminium.•Low phosphate availability supported oxalate exudation when aluminium reached 10 mg/L.•Phosphate's interaction with mobile Al3+ species caused low availability of phosphate.•Aluminium detoxification is only a side-effect due to its chelation from AlPO4.
Among opportunistically pathogenic filamentous fungi of the Aspergillus genus, Aspergillus fumigatus stands out as a drastically more prevalent cause of infection than others. Utilizing the zebrafish ...embryo model, we applied a combination of non-invasive real-time imaging and genetic approaches to compare the infectious development of A. fumigatus with that of the less pathogenic A. niger. We found that both species evoke similar immune cell migratory responses, but A. fumigatus is more efficiently phagocytized than A. niger. Though efficiently phagocytized, A. fumigatus conidia retains the ability to germinate and form hyphae from inside macrophages leading to serious infection even at relatively low infectious burdens. By contrast, A. niger appears to rely on extracellular germination, and rapid hyphal growth to establish infection. Despite these differences in the mechanism of infection between the species, galactofuranose mutant strains of both A. fumigatus and A. niger display attenuated pathogenesis. However, deficiency in this cell wall component has a stronger impact on A. niger, which is dependent on rapid extracellular hyphal growth. In conclusion, we uncover differences in the interaction of the two fungal species with innate immune cells, noticeable from very early stages of infection, which drive a divergence in their route to establishing infections.
In this study, two strains of Aspergillus sp. and Lysinibacillus sp. with remarkable abilities to degrade low-density polyethylene (LDPE) were isolated from landfill soils in Tehran using enrichment ...culture and screening procedures. The biodegradation process was performed for 126 days in soil using UV- and non-UV-irradiated pure LDPE films without pro-oxidant additives in the presence and absence of mixed cultures of selected microorganisms. The process was monitored by measuring the microbial population, the biomass carbon, pH and respiration in the soil, and the mechanical properties of the films. The carbon dioxide measurements in the soil showed that the biodegradation in the un-inoculated treatments were slow and were about 7.6% and 8.6% of the mineralisation measured for the non-UV-irradiated and UV-irradiated LDPE, respectively, after 126 days. In contrast, in the presence of the selected microorganisms, biodegradation was much more efficient and the percentages of biodegradation were 29.5% and 15.8% for the UV-irradiated and non-UV-irradiated films, respectively. The percentage decrease in the carbonyl index was higher for the UV-irradiated LDPE when the biodegradation was performed in soil inoculated with the selected microorganisms. The percentage elongation of the films decreased during the biodegradation process. The Fourier transform infra-red (FT-IR), x-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to determine structural, morphological and surface changes on polyethylene. These analyses showed that the selected microorganisms could modify and colonise both types of polyethylene. This study also confirmed the ability of these isolates to utilise virgin polyethylene without pro-oxidant additives and oxidation pretreatment, as the carbon source.
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