Showing papers on "Aspergillus niger published in 1984"

Glucoamylases G1 and G2 from Aspergillus niger are synthesized from two different but closely related mRNAs

Abstract: By the use of glucoamylase-specific synthetic oligodeoxyribonucleotides and molecular cloning of cDNA synthesized from Aspergillus niger total poly(A) + RNA, the primary structure of the glucoamylase G1 mRNA was determined. Glucoamylase G1 is synthesized as a precursor of 640 amino acid residues containing a putative signal peptide of 18 residues, a short propeptide of six residues and the 616 residues long mature enzyme. In vitro translations of mRNA and immunoprecipitations with glucoamylase-specific antisera showed that two glucoamylase polypeptides are synthesized. The larger form with an apparent mol. wt. of 71 000 corresponds to the precursor of glucoamylase G1, and the shorter form with an apparent mol. wt. of 61 000 corresponds to the precursor of glucoamylase G2. From the nucleotide sequencing data of several glucoamylase-specific cDNA recombinants it is shown that the G1 mRNA contains a 169 bp long intervening sequence that can be spliced out to generate a G2 mRNA. Only the 3' part of the G1 mRNA is modified by this splicing event. This kind of differential mRNA processing to give different protein products from one primary transcript has previously only been demonstrated in higher eukaryotes.

Two different types of intervening sequences in the glucoamylase gene from Aspergillus niger.

Abstract: One single glucoamylase gene could be identified in the chromosomal DNA of Aspergillus niger by Southern blot analysis. This glucoamylase gene was isolated from a genomic library of A. niger DNA. The glucoamylase gene is situated on a 2.5-kb EcoRI-EcoRV fragment and contains five intervening sequences in the coding region. One 169-bp intron is involved in differential mRNA processing leading to the two different glucoamylase enzymes G1 and G2; the other four introns are all very small ranging from 55 to 75 bp in length. One intron has a significant homology to the coding region which immediately follows, and it contains the internal conserved sequence TACTAAC, which is also found in yeast chromosomal gene introns, and is thought to participate in mRNA splicing. Two transcription initiation sites and a typical eukaryotic promoter region with TATAAT and CAAT boxes are located upstream from the gene.

Apple pomace: A potential substrate for citric acid production by Aspergillus niger

Abstract: Apple pomace was used as a fsubstrate for citric acid production by five strains of Aspergillus niger. A. niger NRRL 567 produced the greatest amount of citric acid from apple pomace in the presence of 4% methanol. The yield was 88% based on the amount of sugar consumed.

Apple pomace as substrate for microbial production of citric acid

Abstract: Apple pomace, the residue left from juice extraction, can be employed as a substrate for citric acid production using Aspergillus niger as the fermentation agent.

Morphological development of Aspergillus niger immobilized in Ca-alginate and K-carrageenan

Abstract: The morphological development of citric acid producing Aspergillus niger immobilized in Ca-alginate and K-carrageenan was studied. The fungus normally developed a dense mycelium layer below and on the gel bead surfaces so that substrate and oxygen in this area had direct contact with mycelia. By this way mycelia are not only immobilized by entrapment but also in a “pellet-like” matter. Limitation of the nitrogen source induces a more interior mycelium growth, and outgrowing of free cells was minimized. In sucrose media no effect on the particle stability was observed whereas the application of potassium acetate as substrate caused the complete dissolving of the matrices.

Structural studies on the O‐glycosidically linked carbohydrate chains of glucoamylase G1 from Aspergillus niger

Abstract: Glucoamylase G1 from Aspergillus niger contains an unusual type of carbohydrate-protein linkage, involving mannose O-glycosidically linked to serine and threonine. The majority of the neutral oligosaccharides of glucoamylase G1 are located in a region of about 70 amino acid residues which carries about 35 oligosaccharide units [(1983) Carlsberg Res. Commun. 48, 517–527]. Structural analysis was performed on the O-linked carbohydrates of a tryptic fragment from glucoamylase G1 comprising the segment characterized by a high degree of glycosylation. The carbohydrate structures released by trifluoroacetolysis were elucidated using sugar analysis, methylation analysis, mass spectrometry, chromium trioxide oxidation, digestion with α-mannosidase and 1H-NMR spectroscopy. The following structures could be identified.

Synthesis of Ester Oligomer by Aspergillus niger Lipase

Abstract: Lipase from Aspergillus niger NRRL 337 catalyzed the synthesis of esters from various dicarboxylic acids and diols. Among the esters synthesized, those from 1,13-tridecanedioic acid and 1,3-propanediol were separated by gel permeation chromatography. The constitution of the purified ester was determined by using IR and MS. The dominant components of synthesized esters were pentamer and heptamer, and both end groups of the pentamer and heptamer were hydroxyl.The possible reaction sequence in synthesis of ester oligomer by Aspergillus niger lipase is described.

Evaluation of Phosphorus Solubilisation by Microorganisms Isolated from Aridisols

Abstract: The population of phosphate solubilizing microorganisms was generally low in desertic soils (Aridisols) possibly due to the low level of organic matter and high temperature regime. Bacillus cereus, Pseudomonas florescens, Penicillium pinophillum, and Aspergillus niger were some of the predominant phosphorus solubilizers found in majority of the soils. In vitro evaluation of these cultures indicated that fungi were more efficient than bacteria in phosphorus solubilization. Phosphorus release by all the organisms was associated with the production of organic acids like lactic, glycollic and succinic in the medium. The solubilizing effect of A. niger was progressively enhanced by increasing glucose concentration (0.5 to 2.0%) in the medium, but with rock phosphate such enhancement was not observed beyond 0.25%.

Cloning of Aspergillus niger genes in yeast: expression of the gene coding Aspergillus β-glucosidase

Abstract: The possibility of cloning filamentous fungal genes by expression in the yeast Saccharomyces cerevisiae has been studied. A genome bank of Aspergillus niger was made in E. coli using a yeast cosmid shuttle vector and over 10,000 different cosmid clones were individually isolated. Yeast transformants carrying Aspergillus DNA were screened for the expression of the genes for fungal secreted glycoproteins, β-galactosidase, β-glucosidase, and amyloglucosidase, and for the expression of fungal genes complementing yeast ura3 and leu2 mutations. Of the five Aspergillus genes studied, only one, β-glucosidase, was found to be expressed in yeast, and this at a low level. This suggests that there are essential differences between the genes of yeast and filamentous fungi.

Production of citric acid with immobilized Aspergillus niger

Abstract: The spores of Aspergillus niger were entrapped in calcium-alginate beads and precultivated in growth media with various amounts of nitrogen. During the following citric acid production in shaking cultures an optimum of acid formation and yield was observed after the precultivation with 100–200 mg/l NH4NO3. The productivity of the immobilized Aspergillus was found to be 1.5 times higher than in the case of free pellets. The outgrowth of free mycelia into the medium could be provided by increasing the ratio particle-volume: medium volume, using a 1-l air-lift fermenter, by which means the productivity was increased twice as much as obtained in shaking culture.

The role of tryptophanyl residues in the function of Aspergillus niger glucoamylase G1 and G2

Abstract: The tryptophanyl residues of the Aspergillus niger glucoamylase G1 and G2 (EC 3.2.1.3) were oxidized by N-bromosuccinimide in both the presence and the absence of substrates and inhibitors of the enzyme. In the absence of protective ligands, 8 of 19 and 6 of 15 tryptophanyl residues in G1 and G2, respectively, were susceptible to modification with concomitant inactivation of the enzyme. The binding of acarbose, a potent inhibitor, prior to oxidation protected 2 tryptophanyl residues (Wa and Wb) in both G1 and G2 from the modification. After dissociation of acarbose-enzyme complexes with the aid of Tris, these derivatives retained about 80% of the initial enzymic activity. Further oxidation subsequently modified these 2 tryptophanyl residues resulting in total loss of activity. The substrates, maltose, maltotriose or soluble starch and the inhibitors, gluconolactone, maltitol or deoxynojirimycin protected one tryptophanyl residue (Wb) in both G1 and G2 from oxidation but did not prevent the inactivation. Characterization of the oxidized enzyme derivatives by difference UV absorption and by fluorescence spectroscopy indicated that 2 residues, Wa and Wb, are essential in the mechanism of glucoamylase action. One residue, Wb, is apparently involved in the binding of substrate, while a second, Wa, is an integral part of a catalytically capable active center.

Pretreatment of indian cane molasses for increased production of citric acid.

Abstract: Surface culture citric acid fermentation was carried out by Aspergillus niger T55, a strain isolated from its natural source, using cane molasses, either untreated or treated by various methods. Citric acid biosynthesis is seriously impaired by both organic and inorganic inhibitors. A combined treatment of molasses with tricalcium phosphate, hydrochloric acid, and Sephadex fractionation minimizes the level of inorganic and organic inhibitors in molasses and increases the production of citric acid (65% weight yield based on total reducing sugar). The optimum level of individual metal ions for citric acid production depends on the concentration of other metals in the medium.

Glucoamylase and α-amylase production by immobilized Aspergillus niger

Abstract: Aspergillus niger mycelia or spores were immobilized in calcium alginate gel beads and employed for production of glucoamylase and α-amylase by repeated batch process. The immobilized mycelium produced lower enzyme activities than immobilized spores germinated in a growth medium and subsequently cultured in an enzyme production medium. In repeated batch experiments, free cells could be used for only 4 4-day batches, whereas with immobilized spores at least 11 4-day batches with a gradual increase in enzyme activities in each successive batch were possible. The activity ratio of glucoamylase and α-amylase produced was altered by immobilization.

Pyruvate kinase from Aspergillus niger: a regulatory enzyme in glycolysis?

Abstract: Pyruvate kinase from the filamentous, citric acid producing fungus Aspergillus niger was purified about 100-fold by ammonium sulfate precipitation, DEAE-cellulose chromatography, and gel filtration. The addition of fructose-1,6-diphosphate was necessary to prevent loss of activity during purification. The enzyme purified in the presence of fructose-1,6-diphosphate (FDP) exhibits hyperbolic kinetics with respect to phosphoenolpyruvate (PEP) and ADP. Monovalent cations activated the enzyme (K+, NH4+). FDP neither activated nor inhibited the enzymatic activity from extracts freshly prepared in the absence of exogenous FDP; ATP showed a weak activation. In contrast the enzyme from crude extracts which had been stored in the presence of glycerol for 3 days showed activation by FDP or a metabolite thereof and inhibition by ATP. In the absence of FDP sigmoidal kinetics were obtained with respect to PEP, which became hyperbolic kinetics after addition of FDP. ATP inhibition turned into slight ATP activation in th...

Citrate inhibition of glucose uptake in Aspergillus niger

Abstract: The “in vitro” uptake of glucose and 2-desoxyglucose by whole mycelia of Aspergillus niger, pregrown under citric acid producing conditions, is inhibited by citrate (I 0.5 15 mM), which affects a high affinity glucose transport system (Km 0.14 – 0.17 mM).

Naphtho-gamma-pyrone production by Aspergillus niger isolated from stored cottonseed.

Abstract: Aspergillus niger was found to be the predominant fungal contaminant of stored cottonseed. Seven strains were isolated and grown on rice. The hexane-insoluble material from methylene chloride extracts of 2-week-old cultures contained components toxic to mice. Based on high-pressure thin-layer and liquid chromatographic analyses, the major components in the mixture were eight different naphtho-gamma-pyrones. Of these, the hydrated dimeric naphthopyrones aurasperones B and C occurred in higher yield than aurasperones A, iso-A, and D and the monomeric naphthopyrones flavasperone and rubrofusarin, all of which were present in the mixture. In addition, fonsecin monomethyl ether was isolated. This metabolite may be a precursor in the biosynthesis of the hydrated aurasperones; it has not been identified previously as a metabolite of A. niger. The relative amounts of the different naphthopyrones were dependent on both the growth substrate and the fungal isolate.

Isolation and Identification of ( + )-Hexylitaconic Acid as a Plant Growth Regulator

Abstract: ( + )-Hexylitaconic acid was isolated as a root-growth stimulating substance from a culture filtrate of Aspergillus niger K-88.

Aspergillus niger transformation system

Abstract: Transformants of Aspergillus niger and related Aspergilli, containing foreign DNA conferring modified properties of expression thereon, are prepared by use of a DNA vector which contains a selectable marker which is capable of incorporation into the DNA of the host A. niger cells, but which is not to be found in the A. niger cells prior to this transformation. The vector also contains other foreign DNA to be incorporated into the A. niger, for modified expression. The process suitably uses mutants of A. niger as hosts, the mutants lacking the selectable marker as compared with wild type A. niger, and conducts the transformation on spheroplasts of A. niger.

Enhancement of the in vitro activity of amphotericin B against Aspergillus spp. by tetracycline analogs.

Abstract: Strains of Aspergillus fumigatus, Aspergillus flavus, and Aspergillus niger were tested for in vitro susceptibility to amphotericin B alone and in combination with fixed concentrations of tetracycline, doxycycline, or minocycline, using buffered minimal essential medium in microtiter plates. Enhanced inhibitory activity was seen, especially with combinations of amphotericin B and minocycline. Synergistic activity between amphotericin B and minocycline was observed in each of five isolates of each species when tested in a checkerboard dilution scheme. Time-kill curves demonstrated killing an A. fumigatus isolated at concentrations of amphotericin B that were four- or eightfold lower in the presence of 5 or 15 micrograms of minocycline per ml than with amphotericin B alone. Of the tetracycline analogs tested, minocycline has the greatest activity against A. fumigatus, A. flavus, and A. niger conidia when potentiated by amphotericin B.

Conversion of cassava starch to biomass, carbohydrates, and acids by Aspergillus niger

Abstract: The filamentous fungus, Aspergillus niger, efficiently converted cassava polysaccharides to mycelial mass, simple sugars, and acids during the course of its growth. A typical 70-ml culture broth containing 2% cassava polysaccharides yielded 0.38 g dry mycelial mass, 1.14 mmol reducing sugars, and 1.17 meq acids at the end of 42 h. About 70% of the initial total carbohydrate in the medium was degraded during the same period. The sugars and acids in the culture broths were analyzed by HPLC on a single Aminex HPX-87 column at 55 degrees C, using 0.013 N H2SO4 as the eluting solvent. Cassava polysaccharides were degraded to oligosaccharides, maltotriose, maltose, and glucose beyond the 20-h growth periods, with maltotriose emerging as the major simple sugar. The appearance of citric, malic, gluconic, succinic, and fumaric acids accounted mostly for the decreasing pH in the growth media. Formation of carbohydrate species in the culture broths was closely related to the biosynthesis and secretion of several carbohydrases by A. niger. The extracellular carbohydrases were separated and identified by chromatofocusing and polyacrylamide gel electrophoresis to be amyloglucosidase (EC 3.1.2.3), alpha-amylase (EC 3.2.1.1), and alpha-glucosidase (EC 3.2.1.20), respectively.

Pulmonary oxalosis caused by Aspergillus niger.

Abstract: A case report involving a pleuropulmonary mixed bacterial infection in association with Aspergillus niger is described. The patient responded to a combination of antibiotics, aerosolized and intravenously administered amphotericin B, and surgery. Aspergillus niger appeared to be a secondary invader and caused lung damage by the production of oxalic acid.

Cellulolytic complex of Aspergillus niger under conditions for citric acid production. Isolation and characterization of two β-(1→4)-glucan hydrolases

Abstract: Two β-(1→4)-endoglucanases have been purified from industrial waste broth of Aspergillus niger grown under conditions which produce citric acid. Molecular weights for endoglucanase A were 43,000 and 25,000 for endoglucanase B. Both enzymes exhibited very similar properties: a rather broad pH optimum between pH 2 and 7 for CM-cellulose hydrolysis and an inability to degrade crystalline cellulose. The endoglucanases have a higher thermal stability at acid pH (up to 60°C) than at alkaline pH. They are inhibited by iodine, HgCl2 and N-bromosuccinimide.

Hydroxylation of indolyl-3-acetic acid by immobilized mycelium of Aspergillus niger

Abstract: The immobilization in polyacrylamide gel (PAAG) of the Aspergillus niger mycelium, which has the activity of hydroxylating indolyl-3-acetic acid (IAA) at 4-, 5-, and 6-positions of the indole nucleus, was studied. To preserve the hydroxylating activity, the immobilization should be performed at 5°C–10°C for 5–10 min. The hydroxylating activity of the A. niger mycelium entrapped in PAAG attained 70%–80% of that of free cells. The IAA transformation in the presence of sodium desoxycholate, polyethylene-glycol-400 (PEG-400), Span-60 or preincubation of granules entrapping mycelia in the presence of Tween-80 or PEG-400 not only double the hydroxylation rate but stabilize the activity as well. Gels entrapping mycelia may be used five or six times without altering activity. Incubation of gels with mycelium in the nutrient medium also increases and stabilizes the hydroxylating activity. In aerated columns, it is possible to obtain continuous hydroxylation of IAA, at a concentration of 0.5 g/l, by the immobilized mycelium of A. niger. The yield of hydroxy derivatives reached 70%, the activity remaining unaltered during 15 days' operation of the column.

Formation of the (R)- and (S)-enantiomers of ethyl 3-hydroxybutanoate and of 1-(1,3-dithian-2-yl)-2-hydroxypropane by microbial reduction

Abstract: The (R)and (S) enantiomers of 3-hydroxybutanoate [(2a) or (3a)] and 1-(1,3-dithian-2-yl)-2-hydroxypropane [(2b) or (3b)] are obtained from ethyl 3-oxobutanoate (1a) and 1-(1,3-dithian-2-yl)-2-oxopropane (1b), respectively, using growing cultures from different strains of Geotrichum candidum and Aspergillus niger.

The relationship of structure of glucoamylase and glucose oxidase to antigenicity

Abstract: Glucoamylase and glucose oxidase fromAspergillus niger have been purified to homogeneity by chromatography on DEAE-cellulose and the purified enzymes have been used to investigate structural and antigenicity relationships. In structure, glucoamylase and glucose oxidase are glycoproteins containing 14% and 16% carbohydrate. Earlier methylation and reductive β-elimination results have shown that glucoamylase has an unusual arrangement of carbohydrate residues, with 20 single mannose units and 25 di-, tri-, or tetrasaccharide chains of mannose, glucose, and galactose, all attached O-glycosidically to serine and threonine residues of the protein moiety. The antigenicity of the glucoamylase has now been found to reside predominantly in the types and arrangement of the carbohydrate chains. Glucose oxidase contains mannose, galactose, and glucosamine in the N-acetyl form in the native enzyme, but the complete structure of the carbohydrate chains has not yet been determined. The antigenicity of this enzyme does not reside in the carbohydrate units, but rather in the polypeptide chains of the two subunits of the enzyme. Glucose oxidase can be dissociated into subunits by mercaptoethanol and sodium dodecyl sulfate treatment, while glucoamylase cannot be dissociated, but undergoes only an unfolding of the polypeptide chain under these conditions. The subunits of glucose oxidase do not react with the anti-glucose oxidase antibodies, but the unfolded molecule and peptide fragments produced from glucoamylase by cyanogen bromide cleavage do react with antiglucoamylase antibodies.

Anthranilate hydroxylase from Aspergillus niger: new type of NADPH-linked nonheme iron monooxygenase.

Abstract: Anthranilate hydroxylase from Aspergillus niger catalyzes the oxidative deamination and dihydroxylation of anthranilic acid to 2,3-dihydroxybenzoic acid. This enzyme has been purified to homogeneity and has a molecular weight of 89,000. The enzyme is composed of two subunits of 42,000 with 2 gram-atoms of nonheme iron per mol. Fe2+-chelators like alpha,alpha'-dipyridyl and o-phenanthroline are potent inhibitors of the enzyme activity. Absorption and fluorescence spectra of the enzyme offer no evidence for the presence of other cofactors like flavin. Flavins and flavin-specific inhibitors like atebrin have no effect on the activity of the enzyme. The enzyme incorporates one atom of oxygen each from 18O2 and H218O into the product 2,3-dihydroxybenzoic acid. Based on these studies, it is concluded that anthranilate hydroxylase from A. niger is a new type of NADPH-linked nonheme iron monooxygenase.