Showing papers on "Aspergillus niger published in 2017"

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

Abstract: The filamentous fungal genus Aspergillus consists of over 340 officially recognized species. A handful of these Aspergillus fungi are predominantly used for food fermentation and large-scale production of enzymes, organic acids, and bioactive compounds. These industrially important Aspergilli primarily belong to the two major Aspergillus sections, Nigri and Flavi. Aspergillus oryzae (section Flavi) is the most commonly used mold for the fermentation of soybeans, rice, grains, and potatoes. Aspergillus niger (section Nigri) is used in the industrial production of various enzymes and organic acids, including 99% (1.4 million tons per year) of citric acid produced worldwide. Better understanding of the genomes and the signaling mechanisms of key Aspergillus species can help identify novel approaches to enhance these commercially significant strains. This review summarizes the diversity, current applications, key products, and synthetic biology of Aspergillus fungi commonly used in industry.

Phenolic compounds, flavonoids, lipids and antioxidant potential of apricot (Prunus armeniaca L.) pomace fermented by two filamentous fungal strains in solid state system.

Abstract: The use of agricultural and food by-products is an economical solution to industrial biotechnology. The apricot press residues are abounding by-products from juice industry which can be used as substrates in solid state fermentation process (SSF), thus allowing a liberation and increase of content from various biomolecules with high added value. The evolutions of phenolic levels (by colorimetric assays and high performance liquid chromatography, HPLC–MS) and antioxidant activities (by DPPH assay) during SSF of apricot pomaces with Aspergillus niger and Rhizopus oligosporus were investigated. The changes in fatty acid compositions of oils in apricot kernels during SSFs were also analyzed by gas chromatography (GC–MS). The results showed that the levels of total phenolics increased by over 70% for SSF with R. oligosporus and by more than 30% for SSF with A. niger. A similar trend was observed in the amounts of total flavonoids (increases of 38, and 12% were recorded for SSF by R. oligosporus and A. niger, respectively). Free radical scavenging capacities of methanolic extracts were also significantly enhanced. The main phenolic compounds identified through HPLC–MS in fermented apricot press residues were chlorogenic acid, neochlorogenic acid, rutin, and quercetin 3-acetyl- glucoside. This work also demonstrated that the SSF with filamentous fungal strains not only helped in higher lipid recovery from apricot kernels, but also resulted in oils with better quality attributes (high linoleic acid content). The utilization of apricot by-products resulting from the juice industry as waste could provide an extra income and at the same time can help in solving solid waste management problems

Antifungal activity of water-stable copper-containing metal-organic frameworks.

Abstract: Although metal-organic frameworks (MOFs) or porous coordination polymers have been widely studied, their antimicrobial activities have not yet been fully investigated. In this work, antifungal activity of copper-based benzene-tricarboxylate MOF (Cu-BTC MOF), which is water stable and industrially interesting, is investigated against Candida albicans , Aspergillus niger , Aspergillus oryzae and Fusarium oxysporum . The Cu-BTC MOF can effectively inhibit the growth rate of C. albicans and remarkably inhibit the spore growth of A. niger , A. oryzae and F. oxysporum . This finding shows the potential of using Cu-BTC MOF as a strong biocidal material against representative yeasts and moulds that are commonly found in the food and agricultural industries.

Lactobacillus plantarum with Broad Antifungal Activity as a Protective Starter Culture for Bread Production.

Abstract: Bread is a staple food consumed worldwide on a daily basis. Fungal contamination of bread is a critical concern for producers since it is related to important economic losses and safety hazards due to the negative impact of sensorial quality and to the potential occurrence of mycotoxins. In this work, Lactobacillus plantarum UFG 121, a strain with characterized broad antifungal activity, was analyzed as a potential protective culture for bread production. Six different molds belonging to Aspergillus spp., Penicillium spp., and Fusarium culmorum were used to artificially contaminate bread produced with two experimental modes: (i) inoculation of the dough with a commercial Saccharomyces cerevisiae strain (control) and (ii) co-inoculation of the dough with the commercial S. cerevisiae strain and with L. plantarum UFG 121. L. plantarum strain completely inhibited the growth of F. culmorum after one week of storage. The lactic acid bacterium modulated the mold growth in samples contaminated with Aspergillus flavus, Penicillium chrysogenum, and Penicillium expansum, while no antagonistic effect was found against Aspergillus niger and Penicillium roqueforti. These results indicate the potential of L. plantarum UFG 121 as a biocontrol agent in bread production and suggest a species- or strain-depending sensitivity of the molds to the same microbial-based control strategy.

Combinatorial control of gene expression in Aspergillus niger grown on sugar beet pectin.

Abstract: Aspergillus niger produces an arsenal of extracellular enzymes that allow synergistic degradation of plant biomass found in its environment. Pectin is a heteropolymer abundantly present in the primary cell wall of plants. The complex structure of pectin requires multiple enzymes to act together. Production of pectinolytic enzymes in A. niger is highly regulated, which allows flexible and efficient capture of nutrients. So far, three transcriptional activators have been linked to regulation of pectin degradation in A. niger. The L-rhamnose-responsive regulator RhaR controls the production of enzymes that degrade rhamnogalacturonan-I. The L-arabinose-responsive regulator AraR controls the production of enzymes that decompose the arabinan and arabinogalactan side chains of rhamnogalacturonan-II. The D-galacturonic acid-responsive regulator GaaR controls the production of enzymes that act on the polygalacturonic acid backbone of pectin. This project aims to better understand how RhaR, AraR and GaaR co-regulate pectin degradation. For that reason, we constructed single, double and triple disruptant strains of these regulators and analyzed their growth phenotype and pectinolytic gene expression in A. niger grown on sugar beet pectin.

Comparative genomics and transcriptome analysis of Aspergillus niger and metabolic engineering for citrate production.

Abstract: Despite a long and successful history of citrate production in Aspergillus niger, the molecular mechanism of citrate accumulation is only partially understood. In this study, we used comparative genomics and transcriptome analysis of citrate-producing strains—namely, A. niger H915-1 (citrate titer: 157 g L−1), A1 (117 g L−1), and L2 (76 g L−1)—to gain a genome-wide view of the mechanism of citrate accumulation. Compared with A. niger A1 and L2, A. niger H915-1 contained 92 mutated genes, including a succinate-semialdehyde dehydrogenase in the γ-aminobutyric acid shunt pathway and an aconitase family protein involved in citrate synthesis. Furthermore, transcriptome analysis of A. niger H915-1 revealed that the transcription levels of 479 genes changed between the cell growth stage (6 h) and the citrate synthesis stage (12 h, 24 h, 36 h, and 48 h). In the glycolysis pathway, triosephosphate isomerase was up-regulated, whereas pyruvate kinase was down-regulated. Two cytosol ATP-citrate lyases, which take part in the cycle of citrate synthesis, were up-regulated, and may coordinate with the alternative oxidases in the alternative respiratory pathway for energy balance. Finally, deletion of the oxaloacetate acetylhydrolase gene in H915-1 eliminated oxalate formation but neither influence on pH decrease nor difference in citrate production were observed.

Flocculation mechanism of Aspergillus niger on harvesting of Chlorella vulgaris biomass

Abstract: Fungal flocculation and its mechanism are rarely observed on biofuel-producing microalgae. In this study, the flocculation activity and mechanism of Aspergillus niger hsn26, a filamentous fungus, on Chlorella vulgaris biomass was investigated for the first time. Mycelial pellets showed high flocculation efficiency on algal cells. Moreover, the source of flocculation activity is located at the surface of mycelium. The characteristics of flocculation activity indicated that surface proteins with low molecular weight play a significant role during flocculation process. Calcium can be added into algal culture as coagulants to significantly improve flocculation efficiency. Calcium addition can also simultaneously bind the surfaces of mycelium and algal cells. Therefore, calcium bridging is the main flocculation mechanism for mycelial pellets. The increase of hydrophobic interaction can also promote the flocculation activity. Lastly, results indicate that flocculation mechanism of mycelial pellets on microalgae biomass is a surface proteins-mediated, calcium bridging-dependent and hydrophobic interaction-involved process.

P gas , a Low-pH-Induced Promoter, as a Tool for Dynamic Control of Gene Expression for Metabolic Engineering of Aspergillus niger.

Abstract: The dynamic control of gene expression is important for adjusting fluxes in order to obtain desired products and achieve appropriate cell growth, particularly when the synthesis of a desired product drains metabolites required for cell growth. For dynamic gene expression, a promoter responsive to a particular environmental stressor is vital. Here, we report a low-pH-inducible promoter, Pgas, which promotes minimal gene expression at pH values above 5.0 but functions efficiently at low pHs, such as pH 2.0. First, we performed a transcriptional analysis of Aspergillus niger, an excellent platform for the production of organic acids, and we found that the promoter Pgas may act efficiently at low pH. Then, a gene for synthetic green fluorescent protein (sGFP) was successfully expressed by Pgas at pH 2.0, verifying the results of the transcriptional analysis. Next, Pgas was used to express the cis-aconitate decarboxylase (cad) gene of Aspergillus terreus in A. niger, allowing the production of itaconic acid at a titer of 4.92 g/liter. Finally, we found that Pgas strength was independent of acid type and acid ion concentration, showing dependence on pH only.IMPORTANCE The promoter Pgas can be used for the dynamic control of gene expression in A. niger for metabolic engineering to produce organic acids. This promoter may also be a candidate tool for genetic engineering.

Production, purification and biochemical characterization of an exo-polygalacturonase from Aspergillus niger MTCC 478 suitable for clarification of orange juice

Abstract: Polygalacturonases (PG) represent an important member of pectinases group of enzymes with immense industrial applications A fungal strain Aspergillus niger MTCC478 was used for the production of polygalacturonase both under submerged and solid-state fermentation condition Further its production was optimized under solid-state fermentation condition with media comprising of wheat bran and tea extract Purification of an exo-PG was achieved by acetone precipitation (60–90%) and CM-cellulose column chromatography revealing 1528-fold purification with a specific activity of 3347 U/mg protein and 12% yield A relative molecular mass of purified PG was approximately 1240 kDa The pH and temperature optimum was found to be 4 and 50 °C, respectively The k cat and K m value for degradation of PGA by the purified enzyme was found to be 194 s−1 and 23 mg/mL, respectively Cu2+ was found to enhance the PG activity while Ag+ completely inhibited the enzyme activity The application of the purified PG in orange juice clarification was elucidated

Morphological and Molecular Diversity of Aspergillus From Corn Grain Used as Livestock Feed

Abstract: The study of Aspergillus from corn grains used as livestock feed is important to ensure the safety of the grains as the occurrence of Aspergillus in the corn grain can give an indication of mycotoxin being produced Morphological and molecular identifications were applied to identify Aspergillus isolated from corn grains used as livestock feed Morphologically, six species were tentatively identified, namely Aspergillus niger (Groups I and II), Aspergillus flavus, Aspergillus oryzae, Aspergillus fumigatus, Aspergillus clavatus and Aspergillus terreus Isolates of A niger was divided into two groups based on slight differences of their colony appearances Molecular identification using internal transcribed spacer and β-tubulin sequences supported morphological identification except isolates for A niger Group II isolates, which were molecularly identified as Aspergillus tubingensis Neighbour-joining phylogenetic tree showed that isolates from the same species were grouped in the same clade The present study showed that diverse species of Aspergillus are prevalent in corn grain used as livestock feed It is also necessary to correctly identify the Aspergillus species to employ correct treatment of contaminated corn grains The occurrence of well-known toxigenic species such as A niger, A flavus and A fumigatus suggested the possible risk of mycotoxin contamination of the corn grain

Drug Sensitivity and Resistance Mechanism in Aspergillus Section Nigri Strains from Japan.

Abstract: Aspergillus niger and its related species, known as Aspergillus section Nigri, are ubiquitously distributed across the globe and are often isolated from clinical specimens. In Japan, Aspergillus section Nigri is second most often isolated from clinical specimens following Aspergillus fumigatus We determined the species of Aspergillus section Nigri isolated in Japan by DNA sequencing of partial β-tubulin genes and investigated drug susceptibility by the CLSI M38-A2 method. The collection contained 20 Aspergillus niger, 59 Aspergillus welwitschiae, and 39 Aspergillus tubingensis strains. Drug susceptibility testing revealed 30 to 55% of A. niger, 6.8 to 18.6% of A. welwitschiae, and 79.5 to 89.7% of A. tubingensis isolates to be less susceptible (so-called resistant) to itraconazole (ITC) and/or voriconazole (VRC) according to the epidemiologic cutoff values (ECVs) proposed for A. niger previously. MIC distributions of ITC or VRC showed no remarkable differences between clinical and environmental isolates. When the cyp51A sequences were compared between susceptible and resistant strains, 18 amino acid mutations were specific for resistant isolates of A. niger and A. tubingensis; however, none of them were confirmed to be associated with azole resistance. Three nonrelated A. welwitschiae isolates possessed a partial deletion in cyp51A, likely attributable to being more susceptible to azoles than other isolates. One of five ITC-resistant A. tubingensis isolates showed higher expression of cyp51A than did susceptible strains. Our results show that cyp51A point mutations may have no association with azole resistance but that in some cases the overexpression of cyp51A may lead to the azole resistance in these species.

Production, Optimization and Partial purification of Cellulase by Aspergillus niger fermented with paper and timber sawmill industrial wastes

Abstract: It was the goal to investigate the cellulase enzyme production ability of fungal strain Aspergillus niger against the lignocellulosic bio wastes like saw dust, paper cellulose at varying environmental parameters of pH (4-7), temperature (20-50°C) and incubation period (2-8 days). Production of cellulase was analysed by Dinitrosalicylic acid (DNS) and Filter paper assay methods. In the DNS method, maximum enzyme production of 3.9 IU was achieved at temperature of 45°C by Aspergillus niger in paper cellulose with pH of 5 on 7th day of growth. The partial purification of the cellulase enzyme produced by Aspergillus niger in the waste supplemented medium had two protein bands with the molecular weight of 33 and 24kDa respectively. Key words: Aspergillus niger, paper cellulose, DNS, FPA, Cellulase, Partial purification, Fermentation.

Isolation, identification and optimization of xylanase enzyme produced by aspergillus niger under submerged fermentation

Abstract: The objectives of the present study were isolation, identification and characterization of xylanase producing fungi, optimization of carbon and nitrogen sources and cultural conditions for xylanase enzyme production. A variety of microorganisms were reported to produce endoxylanases, which can degrade s -1, 4-xylan in a random fashion, yielding a series of linear and branched oligosaccharide fragments. The fungal strains were isolated from garden soil by serial dilution technique and Aspergillus niger was identified and isolated in pure form. In conformation screening by congo red test, based on the reddish zone of enzyme activity formation in oat spelt xylan agar plates, Aspergillus niger was selected and optimized for xylanase enzyme production in czapek dox medium using different carbon and nitrogen sources. Maximum enzyme activity was observed in xylan as carbon source and yeast extract as nitrogen source. Optimum pH and temperature for xylanase activity were found to be 8 and 28°C, Thus the present study proved that the fungal strain A .niger used was potential and useful for xylanase production. Key words: Xylanases, submerged fermentation, Aspergillus, optimization.

Enzymatic saccharification of pretreated rice straw by cellulases from Aspergillus niger BK01.

Abstract: Alkali-assisted acid pretreated rice straw was saccharified using cellulase from Aspergillus niger BK01. The cellulase production by the fungus was enhanced by parametric optimization using solid-state fermentation conditions. Maximum cellulase production (12.0 U/gds of carboxymethyl cellulase, CMCase) was achieved in 96 h, using 6.0% substrate concentration, 7.5% inoculum concentration, 1:2 solid to liquid ratio, at pH 5.5, and temperature 28 °C, by supplementation of the fermentation medium with 0.1% carboxymethylcellulose and 0.1% ammonium nitrate. Characterization of crude cellulases showed that highest CMCase activity was observed at pH 4.8 and temperature 40 °C. The CMCase was stable from pH 4.8–5.5 and at a temperature range of 35–50 °C. The pretreated biomass was subjected to hydrolysis with the fungal cellulases. The saccharification optimization studies showed that 2% (v/v) enzyme concentration and hydrolysis time of 2.5 h were optimum for maximum yield, i.e, 23.78% sugars and 35.96% saccharification value.

Bioremediation of Synthetic and Industrial Effluents by Aspergillus niger Isolated from Contaminated Soil Following a Sequential Strategy.

Abstract: The present study aimed to assess and compare the ability to remediate synthetic textile and industrial wastewaters by Fenton treatment, a biological system and sequential treatments using Aspergillus niger (A. niger). All studied treatments were found to be effective in decolorization of the effluents under study. Fenton treatment followed by A. niger showed excellent potential for the maximum decolorization of the synthetic and industrial effluents under study. The effectiveness of sequential treatment was evaluated by water quality parameters such as total organic carbon (TOC), Biological Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) before and after each treatment. The results indicated that A. niger is an effective candidate for detoxification of textile wastewaters.

High-theabrownins instant dark tea product by Aspergillus niger via submerged fermentation: α-glucosidase and pancreatic lipase inhibition and antioxidant activity.

Abstract: BACKGROUND Theabrownins (TB) are bioactive components that are usually extracted from Chinese dark tea, in which they are present at low concentrations. The present study aimed to produce an instant dark tea high in theabrownins via submerged fermentation by the fungus Aspergillus niger. Three fermentation parameters that affect theabrownins content (i.e. inoculum size, liquid–solid ratio and rotation speed) were optimized using response surface methodology. RESULT Optimum fermentation conditions were modeled to be an inoculum of 5.40% (v/v), a liquid–solid ratio of 27.45 mL g−1 and a rotation speed of 184 rpm and were predicted to yield 292.99 g kg−1 TB. Under these experimentally conditions, the TB content of the instant dark tea was 291.93 g kg−1. The antioxidant capacity and α-glucosidase and pancreatic lipase inhibitory activities of the high-TB instant black tea were higher than four other typical instant dark tea products. CONCLUSION The results of the present study show that careful management of culture conditions can produce a dark tea high in theabrownins. Furthermore, high-theabrownins instant dark tea could serve as a source of bioactive products and be used in functional foods as an ingredient imparting antioxidant properties and the ability to inhibit pancreatic lipase and α-glucosidase. © 2017 Society of Chemical Industry

Using an inducible promoter of a gene encoding Penicillium verruculosum glucoamylase for production of enzyme preparations with enhanced cellulase performance

Abstract: Background Penicillium verruculosum is an efficient producer of highly active cellulase multienzyme system. One of the approaches for enhancing cellulase performance in hydrolysis of cellulosic substrates is to enrich the reaction system with β -glucosidase and/or accessory enzymes, such as lytic polysaccharide monooxygenases (LPMO) displaying a synergism with cellulases. Results Genes bglI, encoding β-glucosidase from Aspergillus niger (AnBGL), and eglIV, encoding LPMO (formerly endoglucanase IV) from Trichoderma reesei (TrLPMO), were cloned and expressed by P. verruculosum B1-537 strain under the control of the inducible gla1 gene promoter. Content of the heterologous AnBGL in the secreted multienzyme cocktails (hBGL1, hBGL2 and hBGL3) varied from 4 to 10% of the total protein, while the content of TrLPMO in the hLPMO sample was ~3%. The glucose yields in 48-h hydrolysis of Avicel and milled aspen wood by the hBGL1, hBGL2 and hBGL3 preparations increased by up to 99 and 80%, respectively, relative to control enzyme preparations without the heterologous AnBGL (at protein loading 5 mg/g substrate for all enzyme samples). The heterologous TrLPMO in the hLPMO preparation boosted the conversion of the lignocellulosic substrate by 10–43%; however, in hydrolysis of Avicel the hLPMO sample was less effective than the control preparations. The highest product yield in hydrolysis of aspen wood was obtained when the hBGL2 and hLPMO preparations were used at the ratio 1:1. Conclusions The enzyme preparations produced by recombinant P. verruculosum strains, expressing the heterologous AnBGL or TrLPMO under the control of the gla1 gene promoter in a starch-containing medium, proved to be more effective in hydrolysis of a lignocellulosic substrate than control enzyme preparations without the heterologous enzymes. The enzyme composition containing both AnBGL and TrLPMO demonstrated the highest performance in lignocellulose hydrolysis, providing a background for developing a fungal strain capable to express both heterologous enzymes simultaneously.