Showing papers on "Aspergillus niger published in 2001"
TL;DR: The findings indicate the possibility of exploiting Cymbopogon nardus essential oil as an effective inhibitor of biodegrading and storage-contaminating fungi.
Abstract: The growth inhibitory effect of Cymbopogon nardus (L.) W. Watson var. nardus essential oil on Aspergillus niger (Van Tieghem) mycelium was determined on agar medium. The mycelium growth was complet...
243 citations
TL;DR: Kinetic results on tannase production indicate that low tann enzyme activity titers in SmF could be associated to an enzyme degradation process which is not present in SSF, favoring SSF over SmF.
Abstract: Tannase production by Aspergillus niger Aa-20 was studied in submerged (SmF) and solid-state (SSF) fermentation systems with different tannic acid and glucose concentrations. Tannase activity and productivity were at least 2.5 times higher in SSF than in SmF. Addition of high tannic acid concentrations increased total tannase activity in SSF, while in SmF it was decreased. In SmF, total tannase activity increased from 0.57 to 1.03 IU/mL, when the initial glucose concentration increased from 6.25 to 25 g/L, but a strong catabolite repression of tannase synthesis was observed in SmF when an initial glucose concentration of 50 g/L was used. In SSF, maximal values of total tannase activity decreased from 7.79 to 2.51 IU when the initial glucose concentration was increased from 6.25 to 200 g/L. Kinetic results on tannase production indicate that low tannase activity titers in SmF could be associated to an enzyme degradation process which is not present in SSF. Tannase titers produced by A. niger Aa-20 are fermentation system-dependent, favoring SSF over SmF.
139 citations
TL;DR: Evidence for internal absorption is found as the mechanism used by A. niger to detoxify its environment of copper, a property of the fungus that has not been previously exploited for metal bioremediation.
132 citations
TL;DR: TheXLO2 fusion gene and the XYN2 β-xylanase gene from Trichoderma reesei were successfully expressed and coexpressed in the yeast Saccharomyces cerevisiae under the control of the alcohol dehydrogenase II gene (ADH2) promoter and terminator.
Abstract: Plant cell walls, the major reservoir of fixed carbon in nature, contain three major polymers: cellulose (insoluble fibers of β-1,4-glucan), hemicellulose (noncellulosic polysaccharides including xylans, mannans, and glucans) and lignin (a complex polyphenolic structure) (1, 45). β-1,4-Xylans are found mainly in secondary walls of plants and can represent up to 35% of the total dry weight in certain plants. Xylan is a complex polysaccharide consisting of a backbone of β-d-1,4-linked xylopyranoside units substituted with acetyl, glucuronosyl, and arabinosyl side chains. Endo-β-xylanases (EC 3.2.1.8) act on xylans and xylo-oligosaccharides, producing mainly mixtures of xylooligosaccharides (4, 23). β-d-Xylosidases (EC 3.2.1.37) hydrolyze xylooligosaccharides, produced through the action of β-xylanases, to d-xylose. Many bacterial and fungal species are able to utilize xylans as a carbon source (18). Strains of the fungi Trichoderma and Aspergillus secrete large amounts of efficient xylan-degrading enzymes (8, 16, 51). Recently, interest in β-xylanases has increased because of their application in biobleaching (30, 44) and the food (31) and animal feed (3, 34, 47) industry.
Trichoderma reesei is a filamentous mesophilic fungus that is well known for its cellulolytic and xylanolytic enzymatic activities (12, 43). The two major inducible endo-β-xylanases secreted by this fungus are Xyn1 and Xyn2 (46). They are both relatively small protein molecules, with molecular masses of 19 and 21 kDa, respectively, but Xyn2 represents more than 50% of the total xylanolytic activity of T. reesei cultivated on xylan. Fungi of the genus Aspergillus are also efficient producers of cellulose- and xylan-degrading enzymes, regulated at the transcriptional level by the XlnR activator (49). The two endo-β-xylanases and the β-xylosidase in A. niger are encoded by xlnB, xlnC, and xlnD, respectively. The xlnD gene contains an open reading frame of 2,412 nucleotides, which encodes a protein of 804 amino acids with a predicted molecular mass of 85 kDa. The protein is N glycosylated and contains 15 potential N-glycosylation sites (48). Sequence similarity was found to β-glycosidases (β-xylosidase and β-glucosidases) of family 3, which include enzymes from both bacterial and fungal origins (20, 33, 35, 48). The condensation reaction of this β-xylosidase has been used for the synthesis of disaccharides such as β,β-1,1-xylodisaccharide, β-1,4-xylodisaccharide (xylobiose), β-1,2-xylodisaccharide, α-1,4-xylodisaccharide, and β-1,3-xylodisaccharide (17). S. cerevisiae has been successfully used for the production of related fungal β-xylosidase and β-glucosidases belonging to family 3 (7, 32, 33).
Different Candida species (C. maltosa, C. tropicalis, and C. utilis) are currently used in industry for the production of single-cell protein and ethanol from steamed hemicellulose (21). Even though these Candida strains are able to ferment d-xylose, none of them are able to tolerate the same levels of ethanol as Saccharomyces cerevisiae does, and, furthermore, they cannot ferment hexose sugars as effectively. However, the main disadvantage of S. cerevisiae is the fact that it cannot hydrolyze xylan or utilize or ferment d-xylose, the main component of xylan. While research is continuing on the development of a S. cerevisiae strain able to ferment d-xylose (9, 14, 28, 50), we are working toward the construction of strains able to break down the xylan backbone to its monomeric constituent, d-xylose.
In this paper, we describe the molecular cloning of the A. niger xlnD gene and its expression in S. cerevisiae. Expression and coexpression of xlnD and xyn2 from T. reesei in yeast was obtained with the aid of multicopy plasmids using the derepressible S. cerevisiae alcohol dehydrogenase II gene promoter (ADH2P) and terminator (ADH2T) sequences (38). The enhanced production of both the recombinant enzymes in non-selective complex medium, without the risk of losing the episomal vector, was obtained by constructing autoselective recombinant fur1 S. cerevisiae strains (29).
127 citations
TL;DR: In this article, the removal of lead by waste fungal biomass of Aspergillus niger, originated from citric acid fermentation industry, was investigated, and the experimental results indicated that the bioadsorption achieved equilibrium within 4 h.
122 citations
TL;DR: Formulations of a chitinolytic biocontrol and a plant growth promoting Bacillus subtilis AF 1 promoted seed germination and biomass of both groundnut and pigeon pea even under pathogen pressure and survival of AF 1 on fresh culture-treated and formulation product-treated plants was similar in pathogen-infested soil.
Abstract: Formulations of a chitinolytic biocontrol and a plant growth promoting Bacillus subtilis AF 1 were prepared in peat, in peat supplemented with either 0.5% chitin or Aspergillus niger mycelium, or in spent compost obtained from Agaricus bisporus cultivation and were evaluated for biocontrol of two fungal pathogens and plant growth promoting activities on pigeon pea and groundnut. A steady increase in cell numbers of introduced B. subtilis AF 1 was observed in all the formulations at 30°C. The increase in cell numbers was about 5.0 log units. Peat or spent compost inoculated with physiologically active and dormant states of B. subtilis AF 1 showed different time period requirements to attain maximum cell numbers. The presence of chitin or A. niger (in peat) or A. bisporus (in spent compost) as supplement in the carrier material improved the multiplication of B. subtilis AF 1. When used as seed treatments, formulations of AF 1 in peat supplemented with chitin or chitin-containing materials showed better cont...
121 citations
TL;DR: Analysis for OA in the terrace and barn coffee samples showed that, independent of cultivar, year harvested, or production region, all except one of the samples analyzed showed mycotoxin levels below the limit suggested by the European Common Market (8 microg/kg), thus indicating that the problem is restricted and due to severe faults in harvesting and storage practices.
119 citations
TL;DR: The high levels of exopectinase with sucrose and high Aw in SSF can be explained by a much higher level of biomass production without catabolite repression and with lower protease contamination.
Abstract: Exopectinase production by Aspergillus niger was compared in submerged fermentation (SmF) and solid-state fermentation (SSF). SSF was carried out using polyurethane foam (PUF) as the solid support. The purpose was to study the effect of sucrose addition (0 or 40 g/l) and water activity level (A
w=0.99 or 0.96) on the level of enzyme activity induced by 15 g/l of pectin. Mycelial growth, as well as extracellular protease production, was also monitored. Sucrose addition in SmF resulted in catabolite repression of exopectinase activity. However, in SSF, an enhancement of enzyme activity was observed. Protease levels were minimal in SSF experiments with sucrose and maximal in SmF without sucrose. Exopectinase yields (IU/g X) were negligible in SmF with sucrose. The high levels of exopectinase with sucrose and high A
w in SSF can be explained by a much higher level of biomass production without catabolite repression and with lower protease contamination. Journal of Industrial Microbiology & Biotechnology (2001) 26, 271–275.
119 citations
TL;DR: The results presented demonstrate the capacity of SSC to minimize catabolite repression and the role of gallic acid in tannase regulation was also studied.
104 citations
TL;DR: A dimethoate-degrading enzyme from Aspergillus nigerZHY256 was purified to homogeneity with a specific activity of 227.6 U/mg of protein and was inhibited by most of the metal ions and reagents, while it was induced by Cu2+.
Abstract: A dimethoate-degrading enzyme from Aspergillus niger ZHY256 was purified to homogeneity with a specific activity of 227.6 U/mg of protein. The molecular mass of the purified enzyme was estimated to be 66 kDa by gel filtration and 67 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The isoelectric point was found to be 5.4, and the enzyme activity was optimal at 50 degrees C and pH 7.0. The activity was inhibited by most of the metal ions and reagents, while it was induced by Cu(2+). The Michaelis constant (K(m)) and V(max) for dimethoate were 1.25 mM and 292 micromol min(-1) mg of protein(-1), respectively.
99 citations
TL;DR: Spore suspensions of Aspergillus niger GCB 75, which produced 31.1 g/l citric acid from 15% sugars in molasses, were subjected to u.v.-induced mutagenesis and it was observed that the mutants were faster growing organisms and had the ability to overproducecitric acid.
Abstract: Spore suspensions of Aspergillus niger GCB 75, which produced 31.1 g/l citric acid from 15% sugars in molasses, were subjected to u.v.-induced mutagenesis. Among three variants, GCM 45 was found to be the best citric acid producer and was further improved by chemical mutagenesis using NTG. Out of 3 deoxy-D-glucose-resistant variants, GCM 7 was selected as the best mutant which produced 86.1 ± 1.5 g/l citric acid after 168 h of fermentation of potassium ferricyanide + H2SO4-pretreated black strap molasses (containing 150 g sugars/l) in Vogel's medium. On the basis of comparison of kinetic parameters, namely the volumetric substrate uptake rate (Qs), and specific substrate uptake rate (qs), the volumetric productivity, theoretical yield and specific product formation rate, it was observed that the mutants were faster growing organisms and had the ability to overproduce citric acid.
TL;DR: Kinetic experiments showed that α-Gal I hydrolyzed p-nitrophenyl-α-Image-galactopyranoside and melibiose more efficiently than α-gal II-IV, which further signifies the difference between α- Galactosidases of family 27 and 36.
TL;DR: In this paper, the effect of moisture content of media, glucose, phosphate, some surfactants and gamma irradiation on the production of phytase and reduction of phytic acid in rapeseed meal by Aspergillus niger A-98 (local isolate) during solid state fermentation have been considered.
TL;DR: Pentylferulate synthesis was achieved at high yields (50–60%) with Aspergillus niger feruloyl esterase using a water-in-oil microemulsion system, and the enzyme stability was significantly higher in themicroemulsion than in an aqueous solution.
Abstract: Pentylferulate synthesis was achieved at high yields (50–60%) with Aspergillus niger feruloyl esterase using a water-in-oil microemulsion system The initial rate of synthesis decreased by 15–20% when the water content of the microemulsion was increased from 18 to 24% (v/v), although a concomitant decrease in conversion was not observed The enzyme stability was significantly higher in the microemulsion than in an aqueous solution
TL;DR: To determine the optimum level of initial biomass concentration, n-paraffin concentration, iron concentration and temperature for the production of citric acid, a central composite design was developed using 200 ml batch fermentations.
TL;DR: It was found that palmyra jaggery (sugar syrup from the palmyra palm) is a suitable substrate for increasing the yield of citric acid using Aspergillus niger MTCC 281 by submerged fermentation.
Abstract: The quantitative effects of pH, temperature, time of fermentation, sugar concentration, nitrogen concentration and potassium ferrocyanide on citric acid production were investigated using a statistical experimental design. It was found that palmyra jaggery (sugar syrup from the palmyra palm) is a suitable substrate for increasing the yield of citric acid using Aspergillus niger MTCC 281 by submerged fermentation. Regression equations were used to model the fermentation in order to determine optimum fermentation conditions. Higher yields were obtained after optimizing media components and conditions of fermentation. Maximum citric acid production was obtained at pH 5.35, 29.76 °C, 5.7 days of fermentation with 221.66 g of substrate/l, 0.479 g of ammonium nitrate/l and 2.33 g of potassium ferrocyanide/l.
TL;DR: Glucose oxidase production was optimized using an isolated strain of Aspergillus niger and an economical nutrient source, corn steep liquor, and none of the nitrogen sources was beneficial to the enzyme synthesis.
TL;DR: The aim of this work was to select strains of Aspergillus niger for tannase production, and growth of colonies in plates with tannic acid-containing medium indicated their ability to synthesize tannases.
TL;DR: A protease-deficient strain of Aspergillus niger has been used as a host for the production of human tissue plasminogen activator (t-PA) and active t-PA disappeared from the culture supernatant during the stationary phase of batch cultures, suggesting that the two-chain t- PA may have been incorrectly processed or that initial proteolytic cleavage occurred within the proteolyic domain of the protein.
Abstract: A protease-deficient strain of Aspergillus niger has been used as a host for the production of human tissue plasminogen activator (t-PA). In defined medium, up to 0.07 mg t-PA (g biomass)(-1) was produced in batch and fed-batch cultures and production was increased two- to threefold in two-phase batch cultures in which additional glucose was provided as a single pulse at the end of the first batch growth phase. Production was increased [up to 1.9 mg t-PA (g biomass)(-1)] by the addition of soy peptone to the defined medium. The rate of t-PA production in batch cultures supplemented with soy peptone (0.2 to 0.6 mg t-PA L(-1) h(-1)) was comparable to rates observed previously in high-producing mammalian or insect cell cultures. In glucose-limited chemostat culture supplemented with soy peptone, t-PA was produced at a rate of 0.7 mg t-PA L(-1) h(-1). Expression of t-PA in A. niger resulted in increased expression of genes (bipA, pdiA, and cypB) involved in the unfolded protein response (UPR). However, when cypB was overexpressed in a t-PA-producing strain, t-PA production was not increased. The t-PA produced in A. niger was cleaved into two chains of similar molecular weight to two-chain human melanoma t-PA. The two chains appeared to be stable for at least 16 h in culture supernatant of the host strain. However, in general, <1% of the t-PA produced in A. niger was active, and active t-PA disappeared from the culture supernatant during the stationary phase of batch cultures, suggesting that the two-chain t-PA may have been incorrectly processed or that initial proteolytic cleavage occurred within the proteolytic domain of the protein. Total t-PA (detected by enzyme-linked immunoassay) also eventually disappeared from culture supernatants, confirming significant extracellular proteolytic activity, even though the host strain was protease-deficient.
TL;DR: The recombinant FAEA was purified to homogeneity using a one-step purification protocol and found to be identical to the native enzyme with respect to size, pI, immunoreactivity and N-terminal sequence.
Abstract: The cDNA encoding Aspergillus niger cinnamoyl esterase (FAEA) with its native signal sequence was isolated by reverse transcriptase-polymerase chain reaction, sequenced, and expressed in Pichia pastoris. Secretion yields up to 300 mg l−1 were obtained in buffered medium. The recombinant FAEA was purified to homogeneity using a one-step purification protocol and found to be identical to the native enzyme with respect to size, pI, immunoreactivity and N-terminal sequence. Specific activity, pH and temperature optimum, and kinetic parameters were also found similar to the native esterase. FAEA is thus the first fungal esterase efficiently produced using a heterologous system.
TL;DR: The cloned gene was expressed in the yeast Saccharomyces cerevisiae, in which no cellulase activity was found, and the gene product was purified and subjected to enzymatic characterization, and eng1 was confirmed to encode a very stable endo-beta-1,4-glucanase.
TL;DR: It is demonstrated that citric and oxalic acid and the Aspergillus niger culture filtrates can bind Co 2+ and Zn 2- and in some cases, the culture Filtrates were more efficient than commercial organic acids.
TL;DR: Results suggest that tannases may contribute to plant cell wall degradation by cleaving some of the cross-links existing between cell wall polymers.
TL;DR: Mechanisms involved in bioleaching of an aluminosilicate by heterotrophic microorganisms were investigated and Aspergillus niger and Penicillium purpurogenum and a yeast were isolated.
TL;DR: Simulation results in sugar composition due to the action of a β-fructofuranosidase were in good agreement with the experimental data and a membrane reactor system was developed using nano-filtration membrane, through which glucose permeated but sucrose and fructooligosaccharides did not permeate.
Abstract: Transfructosylation catalyzed by fructooligosaccharide-producing b-fructofuranosidase from Aspergillus niger ATCC 20611 was kinetically studied and a reaction model of transfructosylation was proposed. Kinetic parameters (Vm, Km, and Ki) were determined from experimental data on the transfructosylation rates at various substrate concentrations with and without addition of glucose. Transfructosylation reaction was found to be inhibited non-competitively (Ki=0.12 mol l−1) by glucose. Simulation results in sugar composition due to the action of a β-fructofuranosidase were in good agreement with the experimental data. In order to get higher reaction conversion with a simultaneous removal of glucose, a membrane reactor system was developed using nano-filtration membrane, through which glucose permeated but sucrose and fructooligosaccharides did not permeate. Fructooligosaccharide percentage of the reaction product was increased to above 90%, which was much higher than that of the batch reaction product (55–60%) and comparable to that of the chromatography processed product. The membrane reactor system will be applicable for production of fructooligosaccharides.
TL;DR: Results indicate that this decrease in activity was a combination of sub-optimal enzyme activity and variation in the spectrum of proteases secreted under the different pH conditions.
TL;DR: The nested PCR method specifically identified the A. fumigatus isolates and closely related species and showed a high degree of sensitivity, and suggest further studies for the identification of Aspergillus fumicatus species in clinical specimens.
Abstract: Aspergillus fumigatus is the most common species that causes invasive aspergillosis. In order to identify A. fumigatus, partial ribosomal DNA (rDNA) from two to six strains of five different Aspergillus species was sequenced. By comparing sequence data from GenBank, we designed specific primer pairs targeting rDNA internal transcribed spacer (ITS) regions of A. fumigatus. A nested PCR method for identification of other A. fumigatus-related species was established by using the primers. To evaluate the specificities and sensitivities of those primers, 24 isolates of A. fumigatus and variants, 8 isolates of Aspergillus nidulans, 7 isolates of Aspergillus flavus and variants, 8 isolates of Aspergillus terreus, 9 isolates of Aspergillus niger, 1 isolate each of Aspergillus parasiticus, Aspergillus penicilloides, Aspergillus versicolor, Aspergillus wangduanlii, Aspergillus qizutongii, Aspergillus beijingensis, and Exophiala dermatitidis, 4 isolates of Candida, 4 isolates of bacteria, and human DNA were used. The nested PCR method specifically identified the A. fumigatus isolates and closely related species and showed a high degree of sensitivity. Additionally, four A. fumigatus strains that were recently isolated from our clinic were correctly identified by this method. Our results demonstrate that these primers are useful for the identification of A. fumigatus and closely related species in culture and suggest further studies for the identification of Aspergillus fumigatus species in clinical specimens.
TL;DR: The filamentous fungal strains Aspergillus niger I-1472 and Pycnoporus cinnabarinus MUCL39533, previously selected for the bioconversion of ferulic acid to vanillic acid and vanillin respectively, were grown on sugar beet pulp and number of polysaccharide-degrading enzymes were induced, demonstrating the ability of carbon sources originating from maize to induce the synthesis of feruloyl esterases.
TL;DR: The partial mitochondrial cytochrome b gene from 32 strains of 12 species belonging to Aspergillus section Nigri was amplified by the polymerase chain reaction and sequenced directly and phylogenetic trees were inferred and the genetic divergence among the species was evaluated.
Abstract: The partial mitochondrial cytochrome b gene from 32 strains of 12 species belonging to Aspergillus section Nigri was amplified by the polymerase chain reaction and sequenced directly. Using 402 nucleotide characters, nucleotide-based and amino acid-based phylogenetic trees were inferred and the genetic divergence among the species was evaluated. Based on analyses of the 402-bp nucleotide and 133-amino acid sequences, strains were divided into 11 DNA types and five amino acid types. Aspergillus niger and Aspergillus awamori showed different amino acid sequences. A. niger clade included A. niger var. niger and Aspergillus ficuum. A. awamori clade included A. awamori, Aspergillus phoenicis, Aspergillus pulverulentus, Aspergillus tubingensis, Aspergillus foetidus, and two varieties of A. niger, var. nanus and var. intermedius. Two varieties of A. niger will be reclassified. One strain of A. phoenicis and one strain of Aspergillus carbonarius were reidentified.