Showing papers on "Aspergillus niger published in 1987"
TL;DR: Analysis of the DNA of the A. niger PyrA+ transformants showed that transformation resulted in integration of the vector DNA into the genome by homologous recombination, and both gene replacements and integration of one or more copies of the complete vector have been observed.
Abstract: A homologous transformation system for the filamentous fungus Aspergillus niger has been developed, based on the orotidine-5′-phosphate-decarboxylase gene. A. niger Pyr− mutants have been selected from 5-fluoroorotic acid resistant mutants. These mutants were found to comprise two complementation groups, pyrA and pyrB. The A. niger OMP-decarboxylase gene was isolated from a gene library by heterologous hybridization with the Neurospora crassa pyr4 gene. The cloned gene is capable to transform A. nidulans pyrG mutants at high frequencies. Transformation of A. niger pyrA mutants occurs with moderate frequencies (about 50 transformants/μg DNA) whereas the pyrB mutants cannot be complemented with the cloned OMP-decarboxylase gene. Analysis of the DNA of the A. niger PyrA+ transformants showed that transformation resulted in integration of the vector DNA into the genome by homologous recombination. Both gene replacements and integration of one or more copies of the complete vector have been observed.
173 citations
TL;DR: In this article, a solid-state fermentation method was developed for the production of citric acid from kiwifruit peel by Aspergillus niger NRRL 567.
Abstract: A solid-state fermentation method was developed for the production of citric acid from kiwifruit peel by Aspergillus niger NRRL 567. This method produced about 100g citric acid per kg of kiwifruit peel fermented in the presence of 2% methanol at 30°C in 4 days. The yield was more than 60% based on the amount of fermentable sugar consumed.
121 citations
TL;DR: The results suggest that beneficial effects of these organisms may also be due to the production of growth-promoting substances besides phosphate solubilization.
96 citations
TL;DR: Endo-polygalacturonase was purified from a commercial preparation of Aspergillus niger pectinase by means of carboxymethylcellulose chromatography, preparative isoelectric focusing, and gel permeation through Sephadex G-50 and exhibited a specific activity significantly higher than those of purified polyGalacturonases from phytopathogenic fungi.
Abstract: Endo-polygalacturonase (PG) was purified from a commercial preparation of Aspergillus niger pectinase by means of carboxymethylcellulose chromatography, preparative isoelectric focusing, and gel permeation through Sephadex G-50. The enzyme was electrophoretically homogeneous and consisted of a single polypeptide chain with a molecular weight of 33,500. The enzyme exhibited a specific activity significantly higher than those of purified polygalacturonases from phytopathogenic fungi. Galacturonate oligomers with a degree of polymerization higher than four appeared quickly as products of the enzymic hydrolysis of Napolygalacturonate. The oligomers were later degraded to di- and monogalacturonate. The homogeneous enzyme and growing mycelium of Aspergillus niger separately elicited a necrotic response in cowpea (Vigna unguiculata Walp.) pods. Heat-inactivated PG and PG inactivated with specific antibodies did not elicit necrosis, suggesting that the catalytic activity of the enzyme is necessary for its function as an elicitor. The PG-released oligosaccharides from Vigna cell wall and the galacturonides with a degree of polymerization greater than four separately elicited necrosis, whereas di- and monogalacturonate did not.
92 citations
TL;DR: Ca-alginate beads with entrapped cells of Aspergillus niger showed typical shrinking behaviour, indicating a sponge-like gel structure within the region of enhanced mycelium growth which reduced diffusional resistance of the matrix.
Abstract: This article introduces an easy to handle immobilization apparatus for the entrapment of microbial cells, organelles and enzymes in spherical gel beads Ca-alginate beads with entrapped cells of Aspergillus niger showed typical shrinking behaviour (from 300 mm to 225 mm particle diameter) A loss of stability down to 20% of the initial strength during precultivation of the fungus and within the following citric acid production occurred The observed particle shrinkage was due to the increasing acidification of the medium, whereas the decreased mechanical strength was caused by the entrapped growing microorganism This was confirmed by electron scanning micrographs, indicating a sponge-like gel structure within the region of enhanced mycelium growth which reduced diffusional resistance of the matrix Therefore no differences were found between citric acid production of Ca-alginate entrapped Aspergillus niger at 3 mm and 15 mm initial particle size
85 citations
TL;DR: A transformation system for Aspergillus oryzae based on the orotidine-5′-phosphate decarboxylase gene (pyrG) was developed and efficient cotransformation of an unselectable gene was shown.
Abstract: A transformation system for Aspergillus oryzae based on the orotidine-5′-phosphate decarboxylase gene (pyrG) was developed. Transformation frequencies of up to 16 transformants per μg of DNA were obtained with the vector pAB4-1, which carries the pyrG gene of A. niger. Southern blotting analysis showed that vector DNA sequences were integrated into the chromosomal DNA, in various copy numbers and presumably at different sites. Efficient cotransformation of an unselectable gene was also shown. Under the conditions used no transformants were obtained with the equivalent pyr4 gene of Neurospora crassa.
67 citations
TL;DR: Aspergillus niger lipase, the most suitable of the four enzymes tested, was used for preparative hydrolysis of glucose pentaacetate and gram quantities of pure glucose-2,3,4,6-tetraacetate, glucose triacetate (a mixture of two positional isomers), and glucose-4, 6-diacetate were prepared.
Abstract: Beta-D(+)-glucose pentaacetate was hydrolyzed both chemically and enzymatically. In contrast to the alkaline hydrolysis, esterase-catalyzed deacetylations afforded significant accumulation of intermediate glucose esters at different degrees of substrate conversion. Aspergillus niger lipase, the most suitable of the four enzymes tested, was used for preparative hydrolysis of glucose pentaacetate. As a result, gram quantities of pure glucose-2,3,4,6-tetraacetate, glucose triacetate (a mixture of two positional isomers, 2,4,6- and 3,4,6-), and glucose-4,6-diacetate were prepared.
66 citations
TL;DR: Under the conditions of citric acid fermentation, Aspergillus niger WU-2223L possessed at least two respiratory systems, one of which was sensitive to cyanide (CN) and the other wassensitive to salicylhydroxamic acid (SHAM).
Abstract: Under the conditions of citric acid fermentation, Aspergillus niger WU-2223L possessed at least two respiratory systems. One system was sensitive to cyanide (CN) and the other was sensitive to salicylhydroxamic acid (SHAM). The respiration of mycelia was partially, inhibited by CN or SHAM, and was completely inhibited in the presence of both CN and SHAM. With culture time, the CN-sensitivity of respiration decreased and the SHAM-sensitivity increased. The respiratory rate itself decreased suddenly at 4 days and thereafter remained at a low level. The SHAM-sensitive respiration was localized in the mitochondria. The alterations of respiration in the mitochondria were similar to those observed in mycelial cells.
55 citations
TL;DR: In marked contrast to most enzymes it is found that at pH 6.4 the activity of the fungal catalase from Aspergillus niger is increased on binding of sodium n-dodecyl sulphate (SDS).
53 citations
TL;DR: Endo-arabinanase showed optimal activity on linear arabinan with progressively decreasing activity as the linear sequences were more substituted, and was found to act synergistically with both arabinosidase I and II.
49 citations
TL;DR: It could subsequently be shown that this is caused by the intermediate accumulation and partial re-consumption of a number of polyhydric alcohols (glycerol, arabitol, erythritol and mannitol) during citric acid fermentation.
Abstract: Quantitative balances have been made for sugar and oxygen uptake rates during citric acid accumulation by Aspergillus niger: during the first phase of citric acid accumulation (up to 130 h) more sugar is taken up than the production of biomass, CO2 and citric acid account for. In contrast, during later phases of fermentation more citric acid, CO2 and biomass are formed than sugar uptake would theoretically allow. A similar pattern is obtained for oxygen uptake, where less uptake occurs during the early phase of fermentation than needed for complete balance, and the reverse is observed during the late stage of fermentation. It could subsequently be shown that this is caused by the intermediate accumulation and partial re-consumption of a number of polyhydric alcohols (glycerol, arabitol, erythritol and mannitol) during citric acid fermentation.
TL;DR: Biosynthesis of polygalacturonase (PG) by A. niger strain R 1/214 correlates with the morphology of mycelium in submerged culture and the mean specific PG‐synthesis increases with the degree of compactness ofMycelium.
Abstract: Biosynthesis of polygalacturonase (PG) by A. niger strain R 1/214 correlates with the morphology of mycelium in submerged culture. The mean specific PG-synthesis (PG-U · g−1 · h−1) increases with the degree of compactness of mycelium. PG-production can be optimized by a precise adjustment of the culture conditions after direct spore inoculation (diffuse mycelium) but the high synthesis as by compact mycelium is never obtained. Different reasons for the higher enzyme production by the pellet mycelium are discussed. PG-synthesis is assumed to be strictly connected with a limitation of nutrient and oxygen supply.
TL;DR: The addition of increasing levels of Mn 2+, Fe 3+, Zn 2+ and 4% methanol during citric acid surface fermentation of spent grain liquor by Aspergillus niger (ATCC 9142) was investigated in this article.
TL;DR: The role of fructose 2,6-bisphosphate in the regulation of glycolysis in the citric acid accumulating fungus Aspergillus niger was investigated and it was found that the molecule acted synergistically with AMP, but not with NH+ 4 ions, which otherwise also activate phosphofructokinase.
Abstract: SUMMARY: The role of fructose 2,6-bisphosphate in the regulation of glycolysis in the citric acid accumulating fungus Aspergillus niger was investigated. Fructose 2,6-bisphosphate stimulated the activity of partially purified phosphofructokinase by increasing the affinity of the enzyme for fructose 6-phosphate and relieving inhibition by ATP. Fructose 2,6-bisphosphate acted synergistically with AMP, but not with NH+
4 ions, which otherwise also activate phosphofructokinase. Fructose 2,6-bisphosphate also partially antagonized citrate inhibition of phosphofructokinase; complete deinhibition against high (5 mM) concentrations of citrate (as occur during citric acid accumulation), however, required the simultaneous presence of fructose 2,6-bisphosphate (0·1 μM). AMP (0·1 μM) and NH+
4 ions (20 mM).
TL;DR: The rate of reactivation of reductively denatured ribonuclease A was enhanced by the presence of sulfhydryl oxidase, indicating that the latter is capable of oxidizing protein-associated thiol groups.
Abstract: A procedure for the isolation of a sulfhydryl oxidase from an Aspergillus niger cell suspension involved three major steps and yielded enzyme preparations exhibiting a single but diffuse protein-containing zone when subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis, with a subunit molecular weight estimated to be 53,000. Sedimentation equilibrium experiments indicated a native molecular weight of 106,000. Analyses for sugar residues showed that the enzyme is a glycoprotein, containing 20.3% neutral hexose and 1.9% aminohexose by weight. This enzyme catalyzed the conversion of reduced glutathione (GSH) to its disulfide form, with concomitant consumption of O2 and release of H2O2. The ratio of GSH consumed to H2O2 produced was determined to be 2:1. At 25 degrees C, the optimum pH for the oxidation of GSH was 5.5. Under these conditions, the enzyme had a Michaelis constant of 0.3 mM for GSH. Other low molecular weight thiol compounds (cysteine, dithiothreitol, and 2-mercaptoethanol) were also oxidized, but the Michaelis constants for these substrates were substantially higher than that for GSH under identical conditions of temperature and pH. The rate of reactivation of reductively denatured ribonuclease A was enhanced by the presence of sulfhydryl oxidase, indicating that the latter is capable of oxidizing protein-associated thiol groups. The UV-visible spectrum of sulfhydryl oxidase solution had absorbance maxima at 274, 364.5, and 442.5 nm and was otherwise characteristic of the spectra of known flavoproteins.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: The novelty of this approach was hydrolysis of the raw starch in ground corn to fermentable sugars that are simultaneously fermented to ethanol by yeast in a non‐sterile environment, and the conventional cooking step can be eliminated for energy conservation.
Abstract: The novelty of this approach was hydrolysis of the raw starch in ground corn to fermentable sugars that are simultaneously fermented to ethanol by yeast in a non-sterile environment. Thus, the conventional cooking step can be eliminated for energy conservation. A koji of Aspergillus niger grown on whole corn for 3 days was the crude enzyme source. A ratio of 0.2 g dry koji/g total solids was found sufficient. Optimum pH was 4.2. Ethanol concentration was 7.7% (w/w) in the aqueous phase with 92% raw starch conversion. Agitation increased rate. Sacharification was the rate-limiting step. The initial ethanol concentration preventing fermentation was estimated to be 8.3% by weight.
TL;DR: A method involving fast protein liquid anion exchange chromatography was developed in order to obtain enzyme preparations sufficiently free of enzymes which could interfere with kinetic investigations to identify ATP:citrate lyase in cell-free extracts from the filamentous fungus Aspergillus niger.
Abstract: ATP:citrate lyase (EC 4.1.3.8) has been identified in cell-free extracts from the filamentous fungus Aspergillus niger. The enzyme was located in the cytosol. It exhibits an activity at least ten times that of acetate-CoA-kinase (EC 6.2.1.1) during growth on carbohydrates as carbon sources, and is thus considered responsible for acetyl-CoA formation under these conditions. It is formed constitutively and its biosynthesis does not appear to be controlled by changes in the nitrogen or carbon source or type. ATP:citrate-lyase appears to be very labile during conventional purification procedures; a method involving fast protein liquid anion exchange chromatography was thus developed in order to obtain enzyme preparations sufficiently free of enzymes which could interfere with kinetic investigations. This preparation displays commonly known characteristics of ATP:citrate lyase with respect to substrate affinities and cofactor requirements, with the exception that the affinity for citrate is rather low (2.5 mM). No activator was found. The enzyme is inhibited by nucleoside diphosphates, nucleoside monophosphates and palmitoyl-CoA. Regulation of ATP:citrate lyase be the energy charge of the cytosol in relation to lipid or citric acid accumulation is discussed in view of these findings.
TL;DR: 2,3 dihydroxybenzoic acid (DHBA) decarboxylase from Aspergillus niger was purified to homogeneity by affinity chromatography and did not require any cofactors, nor did the enzyme had any pyruvoyl group at the active site.
TL;DR: The activity of immobilized enzyme preparations towards CMC did not change significantly during continuous operation over a periods of 60 days, the optimum pH of the enzymes shifted to the acidic side in most cases, whereas the optimum temperatures were nearly the same as those of native ones.
Abstract: Commercial cellulase preparations from Trichoderma viride and Aspergillus niger were immobilized on porous silica glass and ceramics such as alumina and titania with titanium tetrachloride (TiCl/sub 4/) and on their silanized derivatives with glutaraldehyde (GLUT). The amounts of the immobilized enzymes were in the range 10-50 mg/g carrier (dry) depending on the kind of carrier and immobilization method. Their activities toward carboxymethyl cellulose (CMC), xylan, aryl-..beta..-glucoside, and aryl-..beta..-xyloside were 3-53% of those of the native enzymes. The optimum pH of the enzymes shifted to the acidic side in most cases, whereas the optimum temperatures were nearly the same as those of native ones. The activity of immobilized enzyme preparations toward CMC did not change significantly during continuous operation over a period of 60 days. Finally, xylan was hydrolyzed with the immobilized enzymes, and the sugars formed were investigated. 22 reference.
TL;DR: Three forms of inulase were purified from Aspergillus niger by ultrafiltration, DEAE-Trisacryl chromatography Sephadex G-150 gel filtration, and preparative isoelectric focusing, and the overall molecular characteristics were similar, but the three forms exhibited distinctly different kinetic constants.
TL;DR: As a result of mutagenization and passaging on 2-deoxy-D-glucose containing medium, Aspergillus niger strains resistant to this agent were obtained and it seems that it can already be successfully utilized to increase the productivity of industrial mould cultures.
TL;DR: The titration curve and amino acid analysis indicate that in the native conformation only 23% of the ionizable amino acid residues are titratable between pH 3 and 10.5.
TL;DR: It is proposed that inhibition of DNA formation in A. niger may be traced back to an impairment of manganese dependent ribonucleotide reduction which provides the monomeric precursors for DNA replication.
Abstract: The effect of managanese on Aspergillus niger ATCC 11414 was studied during the trophophase in a citric acid-accumulating sucrosemineral medium. The absence of manganese ions restricted growth and caused characteristic morphological aberrations. Labelling with (814-C) adenine in-vivo revealed a reversible inhibition of DNA synthesis, but not of RNA synthesis in mycelia starved of manganese. A strong inhibition of DNA synthesis in the presence of 0.2 μM Mn2+ was observed upon addition of 200 mM hydroxyurea (HU) which is known as specific inhibitor of the ribonucleotide reductase. The hypothesis is proposed that inhibition of DNA formation in A. niger may be traced back to an impairment of manganese dependent ribonucleotide reduction which provides the monomeric precursors for DNA replication.
TL;DR: periodic estimations of the essential oil components by gas-liquid chromatography showed a continuous decrease in their concentrations in the culture medium, indicating their removal tending to detoxification.
Abstract: The antifungal activity of two essential oil components (citral and menthol) towards Aspergillus niger and Rhizopus stolonifer was studied in shake culture. The activity was high with lower inoculum density (measured in terms of number of spores ml−1), and it decreased as the inoculum density increased. Citral at 200 μg ml−1 and menthol at 400 μg mh−1 were lethal to the spores of A. niger and R. stolonifer, respectively, after a 48-h treatment. At lower concentrations both the compounds were only fungistatic: the growth of the fungi resumed after an initial delay or upon transfer to fresh medium. Periodic estimations of the essential oil components by gas-liquid chromatography showed a continuous decrease in their concentrations in the culture medium, indicating their removal tending to detoxification. The difference in the activity of the two compounds was related to the capacity of the fungi to detoxify the compounds.
Journal Article•
TL;DR: The citric acid excretion of Ca-alginate-immobilized cells of Aspergillus niger in batch culture decreased with a half-time of approximately 19 days, and could better be prolonged by semicontinuous cultivation with medium exchange every 7 or 14 days, respectively.
Abstract: The citric acid excretion of Ca-alginate-immobilized cells of Aspergillus niger in batch culture decreased with a half-time of approximately 19 days. Reactivation of the biocatalysts by regeneration in growth medium was possible, but it was followed by a submerged sporulation of the fungus, and medium was highly contaminated with free cells. Citric acid production could better be prolonged by semicontinuous cultivation with medium exchange every 7 or 14 days, respectively. After 32 days the remaining activity in semicontinuous culture was 1.4-fold higher than in comparable batch experiments. Similar improvements were obtained with a continuous process at a dilution rate of 0.125 v/v X d, whereby medium efflux kept completely free of detaching mycelia.
TL;DR: The existence of energy-dependent Mn2+ influx in Aspergillus niger ATCC 11414 was demonstrated both with mycelia grown for production of citric acid and in resting mycelian suspended in ‘Good’-buffers.
Abstract: SUMMARY: The existence of energy-dependent Mn2+ influx in Aspergillus niger ATCC 11414 was demonstrated both with mycelia grown for production of citric acid and in resting mycelia suspended in ‘Good’-buffers. A specific high-affinity transport system was detected at submicromolar concentrations of 54Mn2+ which functioned independently of the transport of Mg2+ and Ca2+, but was preferentially inhibited by Zn2+, Cu2+, Cd2+. The rate of Mn2+ transport was suboptimal in the citric acid production medium (pH 3.8 or lower) as the pH optimum was found to be 5.6 in the buffer experiments.
TL;DR: Glyoxalase I catalyzing the conversion of methylglyoxal into S-lactoylglutathione in the presence of glutathione was purified approximately 1,400-fold with 2.9% activity yield from mold, Aspergillus niger.
Abstract: Glyoxalase I catalyzing the conversion of methylglyoxal into S-lactoylglutathione in the presence of glutathione was purified approximately 1,400-fold with 2.9% activity yield from mold, Aspergillus niger. The enzyme consisted of a single polypeptide chain with a relative molecular weight of 36,000 on both SDS-polyacrylamide gel electrophoresis and Sephadex G-150 gel filtration. The enzyme was most active at pH 7.0, 35-37 degrees C. Among the various aldehydes tested, the enzyme was active on methylglyoxal and 4,5-dioxovalerate with Km values of 1.25 and 0.87 mM, respectively. The activity of the enzyme was completely inhibited by Zn2+ at 0.5 mM. An equimolar amount of EDTA (0.5 mM) protected the enzyme from inactivation by Zn2+. EDTA competitively (K1 = 1.3 mM) inhibited the activity of the enzyme. Fe2+ was a potent activator for the enzyme, the activation being approximately 2.4-fold at 0.5 mM.
Journal Article•
TL;DR: Takju, a Korean traditional rice wine, was prepared using Koji and Nuluk which were inoculated with single or combination culture of Aspergillus niger, Shirousamii, and Kawachii to investigate changes in mineral, amino acid and organic acid during fermentation as mentioned in this paper.
Abstract: Takju, a Korean traditional rice wine, was prepared using Koji and Nuluk which were inoculated with single or combination culture of Aspergillus niger, Aspergillus shirousamii, and Aspergillus kawachii to investigate changes in mineral, amino acid and organic acid during fermentation. The mineral content showed a range of for P. It has been found that Takju had 16 kinds of amino acid including aspartic acid. A. niger Nuluk showed the highest contents in total amino acids, while A. kawachii Koji was the lowest in amino acids. The major amino acids were glutamic acid, alanine, leucine, and phenylalanine. The order of organic acids from the highest content in Takju were citric acid> tartaric acid> pyruvic acid> malic acid> lactic acid> acetic acid.
TL;DR: This study examined the effect of A. niger on aflatoxin formation by A. flavus in preharvest maize where the bulk of a flatoxin accumulation occurs.
Abstract: Aspergillus flavus and Aspergillus niger commonly co-occur in preharvest maize and one report suggests that this association promotes a greater incidence of aflatoxin. Other studies have shown that Aspergillus niger can prevent, or substantially reduce, aflatoxin formation by Aspergillus flavus in autoclaved maize kernels, and this led us to examine the effect of A. niger on aflatoxin formation by A. flavus in preharvest maize where the bulk of aflatoxin accumulation occurs. Samples of kernels simultaneously wound-inoculated with equivalent numbers of A. flavus and A. niger conidia showed substantial aflatoxin contamination (mean = 9900 ppb) even though significantly more (P = .04) aflatoxin was produced in kernels wound-inoculated only with A. flavus (mean = 36,700). These same wounded kernels had a mean sample pH of 5.45 ± 0.44, well above substrate acidity levels (