Showing papers on "Aspergillus niger published in 1989"
TL;DR: The results indicate that high concentrations of certain carbon sources are required for high citrate yields, because they induce the appropriate metabolic imbalance required for acidogenesis.
Abstract: The influence of various carbon sources and their concentration on the production of citrate by Aspergillus niger has been investigated. The sugars maltose, sucrose, glucose, mannose and fructose (in the given order) were carbon sources giving high yields of citric acid. Optimal yields were observed at sugar concentrations of 10% (w/v), with the exception of glucose (7.5%). No citric acid was produced on media containing less than 2.5% sugar. Precultivation of A. niger on 1% sucrose and transference to a 14% concentration of various other sugars induced citrate accumulation. This could be blocked by the addition of cycloheximide, an inhibitor of de novo protein synthesis. This induction was achieved using maltose, sucrose, glucose, mannose and fructose, and also by some other carbon sources (e.g. glycerol) that gave no citric acid accumulation in direct fermentation. Precultivation of A. niger at high (14%) sucrose concentrations and subsequent transfer to the same concentrations of various other carbohydrates, normally not leading to citric acid production, led to formation of citrate. Endogenous carbon sources were also converted to citrate under these conditions. A 14%-sucrose precultivated mycelium continued producing some citrate upon transfer to 1% sugar. These results indicate that high concentrations of certain carbon sources are required for high citrate yields, because they induce the appropriate metabolic imbalance required for acidogenesis.
151 citations
TL;DR: A mutant of Aspergillus niger unable to grow on d-xylose and l-arabinose has been isolated and genetic analysis revealed that the mutation is located on linkage group IV.
Abstract: SUMMARY: A mutant of Aspergillus niger unable to grow on d-xylose and l-arabinose has been isolated. Genetic analysis revealed that the mutation is located on linkage group IV. Enzymic analysis revealed a deficiency in d-xylulose kinase activity. After transfer of growing mycelium to a medium containing either d-xylose or l-arabinose, the mutant accumulates large amounts of arabitol and xylitol, as shown by 13C NMR spectroscopy. These data and an analysis of enzyme activities induced by d-xylose and l-arabinose in the wild-type strain led to the following catabolic pathway for d-xylose: d-xylose - xylitol - d-xylulose - d-xylulose 5-phosphate; and for l-arabinose: l-arabinose - l-arabitol - l-xylulose - xylitol - d-xylulose - d-xylulose 5-phosphate. The reduction steps of the sugars to the corresponding polyols are all NADPH dependent. The oxidation steps of the polyols to the sugars are all NAD+ dependent. Fractionation of cell-free extracts gave information about the specificity of the enzymes and showed that all the reactions are catalysed by different enzymes.
141 citations
TL;DR: Analysis of genomic endonuclease cleaved DNA from nitrate utilising transformants by DNA hybridisation, showed that most integration events are as a result of homologous recombination.
Abstract: Aspergillus niger transformation frequencies of up to 1,176 transformants per μg DNA were achieved using the plasmid vector pSTA10 containing the A niger nitrate reductase structural gene Analysis of genomic endonuclease cleaved DNA from nitrate utilising transformants by DNA hybridisation, showed that most integration events are as a result of homologous recombination The niaD transformation system was used successfully for the introduction of the unselected Escherichia coli fusion genes lacZ, encoding β-galactosidase, and uidA, for β-glucuronidase, as well as the Neurospora crassa tub-2 gene, for β-tubulin pSTA10 was also capable of transforming niaD mutants of other filamentous fungi such as A nidulans, A oryzae and Penicillium chrysogenum
127 citations
TL;DR: The β-fructofuranosidase showed a high regiospecificity to transfer the fructosyl moiety for the 1-OH group of terminal fruct ofuranosides in cells of Aspergillus niger ATCC 20611.
Abstract: A fructooligosaccharide-producing β-fruetofuranosidase was purified from cells of Aspergillus niger ATCC 20611. The molecular weight was 340,000 by gel filtration. The optimum pH of the enzyme was 5.0 ~ 6.0 and the optimum temperature was 50~60°C. The enzyme was rendered inactive by 1 mM Hg2+ and the Km value for sucrose was 0.29 m. The enzyme catalyzed an almost exclusively fructosyl transfer reaction in a 50% sucrose solution to produce a mixture of fructooligosaccharides and glucose, but both fructosyl transfer and hydrolytic action were observed in a 0.5 % solution. The β-fructofuranosidase showed a high regiospecificity to transfer the fructosyl moiety for the 1-OH group of terminal fructofuranosides.
125 citations
TL;DR: A cDNA library from Aspergillus niger strain NRRL‐3 enriched in sequences encoding the glucose oxidase was constructed and the deduced protein sequence was verified by partial peptide sequencing.
97 citations
TL;DR: Tests showed that the highest yield of solubilized zinc occurred with a 2.5% substrate (93% zinc extracted after 13 days), while the formation of citric acid by Penicillium sp.
Abstract: Zinc was extracted from a filter residue of a copper works (58.6% zinc) by a Penicillium sp. isolated from a metal-containing location. By isotachophoresis citric acid was identified as the leaching agent. Citrate was only formed when the leaching substrate was present. This production of citrate was different in several ways from that achieved by Aspergillus niger: glucose was utilized before fructose; the initial concentration of zinc was 50 to 500 times higher than usual in citrate fermentations with A. niger; citrate production stopped when 80 to 90% of the zinc was leached, although sufficient sugar for further synthesis was still present; and in synthetic media citrate production by A. niger needs an acidic environment (pH 2), while the formation of citric acid by Penicillium sp. occurred in a pH range of 7 to 4. Tests with different concentrations of waste material (0.5, 2.5, and 5%) showed that the highest yield of solubilized zinc occurred with a 2.5% substrate (93% zinc extracted after 13 days).
88 citations
TL;DR: The change from nitrogen-limited to phosphate-limited precultivation of immobilized spores significantly increased the productivity of the mycelium and the ratio of citric acid to residual sugar in the effluent distinctly lay in the direction ofcitric acid.
Abstract: Immobilized cells of Aspergillus niger needed a lower initial sucrose concentration than free cells in order to obtain maximal yields of citric acid production. High sucrose concentrations led to reduced yields and increased polyol formation (glycerol, erythritol, arabitol). Continuous fermentation with media containing low sugar concentrations prevented the formation of polyols. The change from nitrogen-limited to phosphate-limited precultivation of immobilized spores significantly increased the productivity of the mycelium. The ratio of citric acid to residual sugar in the effluent distinctly lay in the direction of citric acid. Inside the alginate beads mainly large bulbous cells were observed.
79 citations
TL;DR: Determination of the activities of endo-1,4-β-glucanase, exo-2,3,3- β- glucanases of the cellobiohydrolase I type (hydrolysing 4-nitrophenyl β-lactoside), β-Glucosidase, endo,1, 4-β -xylanase and β-xylosidases showed that Aspergillus terre
73 citations
TL;DR: Biodegradation of hemicelluloses requires enzyme activities that remove nonxylose substituents from the xylan backbone in addition to endoxylanases and β-xylosidases, andraction of crude enzymes indicated that the 4-o-methylglucuronidases were polydisperse.
Abstract: Biodegradation of hemicelluloses requires enzyme activities that remove nonxylose substituents from the xylan backbone in addition to endoxylanases and β-xylosidases Activities removing o-acetyl, arabinose, cinnamic acid-based esters, and uronic acid substituents occurred inStreptomyces olivochromogenes, Aspergillus niger, andSchizophyllum commune 4-O-Methylglucuronidase was coinduced with other substituent-hydrolyzing enzymes when appropriate lignocellulosic materials were provided Fractionation of crude enzymes indicated that the 4-o-methylglucuronidases were polydisperse The 4-o-methylglucuronidases fromS commune andA niger acted on high molecular weight heteroxylans, but those from Solivochromogenes functioned only with small, endo-β-(1,4)-xylanse-solubilized fragments
72 citations
TL;DR: A homologous transformation for Aspergillus niger was developed based on the nitrate reductase structural gene niaD, and it was demonstrated that while some transformants were as stable as the wild-type (wt), others were markedly less so.
68 citations
TL;DR: Glucoamylase, industrially derived from Aspergillus niger, was chromatographically separated into forms I and II and purified to near homogeneity, proved to be free of D‐glucosyltransferase by electrophoretic and differential inhibition tests.
Abstract: Glucoamylase, industrially derived from Aspergillus niger, was chromatographically separated into forms I and II and purified to near homogeneity Preparations were proved to be free of D-glucosyltransferase by electrophoretic and differential inhibition tests Maximum rates and Michaelis constants were obtained for both glucoamylases I and II with maltooligosaccharides from maltose to maltoheptaose and with isomaltooligosaccharides from isomaltose to isomaltohexaose Subsite maps were calculated from these kinetic data and were not significantly different for the two forms Subsites in both forms had lower affinities for D-glucosyl residues contained in isomaltooligosaccharides than for D-glucosyl residues in maltooligosaccharides
TL;DR: Aspergillus niger NRRL-3, an organism used for the industrial scale production of d-gluconic acid and glucose oxidase (EC 1.3.1.4), was subjected to mutagenesis and selection for acid production on diagnostic media containing methyl red.
Abstract: Aspergillus niger NRRL-3, an organism used for the industrial scale production of d-gluconic acid and glucose oxidase (EC 1.1.3.4), was subjected to mutagenesis and selection for acid production on diagnostic media containing methyl red. The plates contained 0.1 M d-glucose, a concentration that does not produce a color change in the medium surrounding mycelia of the parental strain under the conditions employed. Mutagenized spores yielded occasional colonies which were able to grow rapidly and were surrounded by a reddish zone. A number of such presumptive mutants were selected and isolated. Twenty-six such strains were grown in shaken cultures with liquid media containing 0.01, 0.1 or 0.5 M d-glucose, harvested, disrupted and the specific activity of d-glucose oxidase determined. Seven of the mutant strains had glucose oxidase specific activities markedly higher than the parental strain.
TL;DR: The fact that strong selection for either sC+ or sC- can be applied provides a simple way of delivering genetically engineered constructs to any strain of A. niger including strains of industrial importance and is useful for gene replacements and other genomic DNA manipulations in Aspergillus species.
TL;DR: Citric acid was produced using Aspergillus niger immobilized on polyurethane foam in a bubble column reactor because most of the adsorbed cells remained on the support and, as a result, high oxygen tension was maintained during the reactor operation.
Abstract: Citric acid was produced using Aspergillus niger immobilized on polyurethane foam in a bubble column reactor. Most of the adsorbed cells remained on the support and, as a result, high oxygen tension was maintained during the reactor operation. However, uncontrolled growth of the pellets made continuous reactor operation difficult. The citric acid productivity obtained from 15 vol.% foam particles containing immobilized cells was 0.135 g/l per hour. This productivity of immobilized cells was almost the same as that of free cells. The oxygen level dropped to half saturation in 5 days in the immobilized cell culture in contrast to 2 days in the free cell culture.
TL;DR: The effect of the enzyme on the conversion of wort saccharides into glucose has been quantified and a procedure, based on the use of phenyl α- d -glucopyranoside as substrate, is recommended for the assay of this enzyme in crude culture filtrates.
TL;DR: The deduced total amino acid sequence of GAI contained 35 replacements and one deletion, of amino acid residues, and therefore a total of 615 residues, in comparison with the A. niger and A. awamori glucoamylases.
Abstract: The raw-starch-digesting glucoamylase I (GAI) of Aspergillus awamori var. kawachi contains a glycopeptide I (Gp-I) region as the raw-starch-affinity site essential for its raw-starch-adsorption and raw-starch-digestion. Molecular cloning of the GAI gene and analysis of its nucleotide sequence revealed some nucleotide replacements, in comparison with the Aspergillus niger and Aspergillus awamori glucoamylase genes. The deduced total amino acid sequence of GAI contained 35 replacements and one deletion, of amino acid residues, and therefore a total of 615 residues, in comparison with the A. niger and A. awamori glucoamylases. The raw-starch-adsorbable Gp-I region in GAI was located between Ala470 and Val514 near the C-terminal, consisting of ATGG- TTTTATTTGSGGVTSTSKTTTTASKTSTTTSSTSCTTPTAV.
TL;DR: Redox potential and pH values proved to be valuable indicators of the initiation and end of enzyme synthesis in the production of a pectolytic enzyme complex in a 10-l strirred tank bioreactor using Aspergillus niger mutant A 138.
Abstract: The production of a pectolytic enzyme complex in a 10-l strirred tank bioreactor was studied using the Aspergillus niger mutant A 138. A time course of the fermentation showed that the enzyme synthesis is not associated with growth. Maximal activity was reached after 95 h and from that time on it remained constant. Redox potential and pH values proved to be valuable indicators of the initiation and end of enzyme synthesis. The specific morphology of the fungus, growing in distinct pellets with long peripheral hyphae, resulted in a very dense and viscous broth. It represented a special problem for heat and mass transfer. An attempt was made to overcome this problem by different agitation and aeration regimes. These parameters did not change the morphology but had a marked influence on enzyme synthesis. When, at the time of maximal growth rate, aeration was increased from 0.5 vvm to 1.2 vvm, and agitation from 300 rpm to 500 rpm, the depectinizing activity was doubled in comparison with the results obtained when 0.5 vvm and 300 rpm were used throughout fermentation. When more intensive agitation was employed from the beginning of the process, the depectinizing activity was lowered from 60 to 45 units/ml, together with the viscosity and polygalacturonase activity. However, at the same time, the pectin esterase and pectinlyase yields increased. The required fermentation time was reduced from 95 to 65 h.
TL;DR: Batch production of gluconic acid in the presence of a high concentration of glucose was investigated using free and immobilized mycelia of Aspergillus niger IAM 2094 with the aim of achieving repeatable constant production.
TL;DR: Results show that the N-linked sugar chains of the glucose oxidase contributed to the high solubility of the enzyme in water.
Abstract: Endo-β-N-acetylglucosaminidase from Flavobacterium sp. released about 30% of the N-linked sugar chains from the glucose oxidase of Aspergillus niger. To elucidate the role of the carbohydrate moiety, the enzymatic properties of native and carbohydrate-depleted glucose oxidases were compared. It was found that their catalytic activities and thermal and pH stabilities were identical. However, the carbohydrate-depleted glucose oxidase was more rapidly precipitated by the addition of trichloroacetic acid and ammonium sulfate than the native enzyme. These results show that the N-linked sugar chains of the glucose oxidase contributed to the high solubility of the enzyme in water.Key words: glucose oxidase, Aspergillus niger, carbohydrate depletion, endo-β-N-acetylglucosaminidase, enzyme stability.
TL;DR: This procedure gave transformation frequencies similar to those obtained with polyethylene glycol and no differences were observed between the two procedures with respect to the number of integrated plasmid copies or the frequency of homologous integration.
TL;DR: Biochemical analysis of the cotransformants indicated that in nearly all cases the fusion gene had replaced the wild-type trpC gene, which is not linked to any of the A. niger loci described so far.
Abstract: Aspergillus niger tryptophan auxotrophic mutants have been isolated after UV irradiation of conidiospores. The mutants belong to two different complementation groups, trpA and trpB, which complement each other in heterokaryons. Neither of the mutations could be complemented with the cloned A. niger trpC gene. To obtain A. niger trpC mutants in a direct way, gene inactivation by cotransformation was performed. For this purpose an in-frame gene fusion between the A. niger trpC and Escherichia coli lacZ genes was constructed and shown to be functionally expressed after introduction into A. niger by cotransformation with the pyrA gene as selective marker. Among the β-galactosidase expressing cotransformants, obtained with either circular or linearized vectors, no trpC mutants were detected, even after enrichment. Such mutants, however, could be obtained by cotransformation of A. niger with specific fragments of the fusion gene. Biochemical analysis of the cotransformants indicated that in nearly all cases the fusion gene had replaced the wild-type trpC gene. Genetic analysis showed that the trpC mutation is not linked to any of the A. niger loci described so far. The trpC mutants can be complemented by the cloned A. niger trpC gene as well as by the A. nidulans trpC gene.
TL;DR: The synthesis of pectinesterase and polygalacturonase by a strain of Aspergillus niger isolated from rotten lemons was repressed by glucose, even in the presence of the inducer, suggesting that repression occurs at the translational level.
Abstract: The synthesis of pectinesterase (PE) and polygalacturonase (PG) by a strain ofAspergillus niger isolated from rotten lemons was repressed by glucose, even in the presence of the inducer. The production of both enzymes started again once the sugar was used up, or when the mycelium was washed free of glucose and incubated in a glucose-free medium containing the inducer; this proved the reversibility of the repression mechanism. The effect of glucose was also tested in the absence of transcription. The results obtained suggest that repression occurs at the translational level.
TL;DR: Glycerol, which functions as an osmoregulator in the early stages of Aspergillus niger growth, slowly diffuses out of the cells and possibly into the mitochondria, and citrate starts to accumulate in the cells.
Abstract: Glycerol, which functions as an osmoregulator in the early stages of Aspergillus niger growth, slowly diffuses out of the cells and possibly into the mitochondria. Since mitochondrial nicotine adenine dinucleotide phosphate (NADP+)-specific isocitrate dehydrogenase is inhibited by glycerol, citrate starts to accumulate in the cells. At physiological pH values citric acid dissociates and affects the intracellular and extracellular pH. By the phosphorus-31-nuclear magnetic resonance technique a drop in intracellular pH from 7.1 to about 6.5 has been detected, which might significantly influence metabolic rates.
TL;DR: Mutants of Aspergillus niger were selected according to their ability to grow faster than the parent strain on solid media containing 14% (w/v) sucrose and exhibited significantly increased citric acid production and strongly increased activities of two glycolytic enzymes.
Abstract: Mutants of Aspergillus niger were selected according to their ability to grow faster than the parent strain on solid media containing 14% (w/v) sucrose. Among 9 mutants, 4 exhibited significantly increased (> 20% of control) citric acid production. These mutants exhibited strongly increased activities of two glycolytic enzymes, hexokinase and phosphofructokinase. The mutants took up low concentrations (1%, w/v) sucrose at a comparable rate to the parent strain but exhibited a faster uptake of high (14%, w/v) sucrose concentrations.
TL;DR: The raw-starch-affinity site of Aspergillus awamori var.
Abstract: The raw-starch-affinity site of Aspergillus awamori var. kawachi glucoamylase I (GAI), that was proved to be essential for its adsorbability and digestibility on raw starch granules, was found to be located separately from the active site in the region corresponding to glycopeptide I (Gp-I) liberated from the glucoamylase I through the action of subtilisin. Gp-I consists of 45 amino acid residues, hydroxy amino acids being characteristically abundant, and 56 mannose residues. The sequence was determined with an automatic amino acid sequencer to be A T G G T T T T A T T T G S G G V T S T S K T T T T A S K T S T T T S S T S C T T P T A V. A structure of parallelly arranged short mannoside chains linked o-glycosidically to the successive sequence of hydroxy amino acid residues on Gp-I was revealed. On comparison of the amino acid sequence of Gp-I with those of three glucoamylases, from Aspergillus awamori, Aspergillus niger and Rhizopus oryzae, significantly homologous regions (91 %, 91 % and 77 % homology, ...
TL;DR: A heterologous gene mediated transformation system based on niaD, the structural gene encoding nitrate reductase, has been developed for Penicillium chrysogenum and it was demonstrated that vector sequences had integrated into the recipient genome.
Abstract: A heterologous gene mediated transformation system based on niaD, the structural gene encoding nitrate reductase, has been developed for Penicillium chrysogenum. Transformation frequencies of up to 20 transformants per microgram DNA were obtained using the Aspergillus nidulans gene and 9 transformants per microgram using the A. niger gene. Vector constructs carrying the A. nidulans ans-1 sequence and the A. niger niaD gene did not show increased transformation frequencies. Southern blot hybridisation analysis demonstrated that vector sequences had integrated into the recipient genome. The control of heterologous niaD gene expression generally agreed with that found in the wild-type strain, that is, induction by nitrate and repression in the presence of ammonium.
TL;DR: Experiments performed in batch fermentation under phosphate-limited growth conditions showed that the citric acid yield was inversely related to the excess nitrogen concentration in the medium, evidence for nitrogen catabolite repression.
Abstract: Experiments performed in batch fermentation under phosphate-limited growth conditions showed that the citric acid yield was inversely related to the excess nitrogen concentration in the medium. Results from chemostat culture confirmed a negative relationship between the citric acid yield and both the specific growth rate and the nitrogen consumption rate. This is evidence for nitrogen catabolite repression. A fed-batch fermentation performed under dual phosphate/nitrogen limitation produced results very similar to those from a culture limited by nitrogen alone. There is no advantage in maintaining an excess of phosphate during citric acid production and the process will therefore be more economic when operated under dual limitation conditions.
TL;DR: A non-purified preparation of intracellular acid phosphatase from a waste mycelium of Aspergillus niger was utilised for dephosphorylation of phytate compounds present in food and feed ingredients, and in the gastrointestinal tract of broilers the in-vivo de phytates present in feed was observed.
Abstract: A non-purified preparation of intracellular acid phosphatase (EC 3.1.3.2) from a waste mycelium of Aspergillus niger was utilised for dephosphorylation of phytate compounds present in food and feed ingredients. The enzymic hydrolysis of p-nitrophenylphosphate was used for assaying acid phosphatase activity, expressed in standard units (u).
The hydrolysis of phytate phosphorus in wheat bran, soya bean meal and fully formulated feedstuffs for broilers (Galus galus; ‘Cornish’ × White Rock') was carried out at 40°C, a pH value of 4.5 and an enzyme dosage ranging from 12 to 30 u g−1. Complete dephosphorylation of soya bean protein isolates was performed at 60°C, a pH value of 4.5 and an enzyme dosage of 12 u g−1. In the gastrointestinal tract of broilers the in-vivo dephosphorylation of phytates present in feed was observed when the preparation of acid phosphatase was added to the diet.
TL;DR: An alfalfa-root saponin (compound F) was isolated and its chemical structure determined as 3β-[ O -α-d -glucopyranosyl-(1→4)-β- d -glocopyranoyl]-2β-hydroxy-Δ 12 -oleanene-23,28-dioic acid (3β-medicagenic acid β-maltoside).
TL;DR: In this article, the production of cellulases and β-glucosidase using locally-isolated Aspergillus niger on various cheap sources of cellulose like bagasse, corn corbs, computer cards and sawdust was studied.