Showing papers on "Aspergillus niger published in 1980"

Culture Method to Study Fungal Growth in Solid Fermentation

Abstract: A new culture method is described to study the growth of Aspergillus niger on cassava meal in the solid state. This method uses preparations of the cooked starchy substrate as a homogeneous granulated product containing spores, salts and water. An incubation device aerates the mass with humidified air at a controlled temperature. Homogeneous development of mycelia, without sporulation, occurred in the substrate mass. From physiological studies, optimal conditions for A. niger growth on cassava in the solid state were 50–55% moisture, 35°C, a nitrogen source comprising 60% ammonium and 40% urea (on a nitrogen basis) and 2×107 spores/g of substrate. Growth kinetics were established and changes in pH, protein, carbohydrate and water content were determined during the incubation. Growth rate and yield were quite similar to those described in the literature for A. niger cultivated in liquid media under optimal conditions.

Chelating, film‐forming, and coagulating ability of the chitosan–glucan complex from Aspergillus niger industrial wastes

Abstract: Waste mycelia of Aspergillus niger from a citric acid production plant are simply treated with boiling 30-40% NaOH aqueous solutions for 4-6 hr to obtain the insoluble chitosan-glucan complex whose infrared, ESR, and x-ray diffraction spectra are reported. A number of transition- and post-transition-metal ions are chelated and collected by chitosan-glucan with higher yields than by animal chitosan. Immediate flocculation occurs upon mixing chitosan-glucan dispersions with alginate and polymolybdate solutions. Membranes are also obtained from chitosan-glucan dispersions in acetic acid or in chloral and dimethyl formamide mixtures.

Regulation of citric acid production by oxygen: Effect of dissolved oxygen tension on adenylate levels and respiration in Aspergillus niger

Abstract: The mechanism of the control of citric acid accumulation by oxygen was investigated by means of pilot plant fermentation using Aspergillus niger. The critical dissolved oxygen tension (DOT) for oxygen uptake of this fungus was about 18–21 and 23–26 mbar for trophophase and idiophase, respectively. Minimal DOT for citric acid production was about 25 mbar. Citric acid production increased steadily between 40–150 mbar. Short time changes in the DOT produced immediate, irreversible changes in the rate of product formation. Adenine nucleotides paralleled growth but showed no evidence for control function in the oxygen effect on citric acid fermentation. A branched respiratory system was identified by experiments using specific inhibitors (antimycin, cyanide, azide, rotenone, amytal and salicylhydroxamic acid). Growth was sensitive towards inhibitors of the standard respiratory chain, but only slightly sensitive towards salicylhydroxamic acid (SHAM). Citric acid synthesis was highly sensitive towards SHAM during trophophase, but sensitive towards antimycine during idiophase. Interruptions in aeration cause an impairment of the SHAM sensitive oxidase during trophophase, and of the antimycin sensitive oxidase during idiophase.

Influence of manganese on morphology and cell wall composition of Aspergillus niger during citric acid fermentation.

Abstract: Morphology and cell wall composition of Aspergillus niger were studied under conditions of manganese sufficient or deficient cultivation in an otherwise citric acid producing medium. Omission of Mn2+ (less than 10-7 M) from the nutrient medium of Aspergillus niger results in abnormal morphological development which is characterized by increased spore swelling, and squat, bulbeous hyphae. Fractionation and analysis of manganese deficient cell walls revealed increased chitin and reduced β-glucan contents as well as reduction of galactose containing polymers, as compared to cell walls from manganese sufficient grown hyphae. Addition of copper induced the same effect as manganese deficiency, both on morphology and cell wall composition. Addition of cycloheximide also produced a very similar type of morphology with increased chitin and reduced β-glucan contents of the cell wall but its effect on galactose was less pronounced.

Cytochemical Localization of Glucose Oxidase in Peroxisomes of Aspergillus niger

Abstract: The subcellular localization of glucose oxidase (E.C. 1.1.3.4) in mycelia of Aspergillus niger has been investigated using cytochemical staining techniques. Mycelia from fermenter cultures, which produced gluconic acid from glucose, contained elevated levels of glucose oxidase and catalase. Both enzymes were located in microbodies. In addition, when the organism was grown on glucose with methylamine as a nitrogen source, amine oxidase activity was detected in the microbodies. These organelles can therefore be designated as peroxisomes.

High‐yield method for immobilization of enzymes

Abstract: Two types of polyethylenimine-coated glass microbeads (13-44 micrometer) were synthesized and used for the immobilization of glucose oxidase from Aspergillus niger and catalase from A. niger and beef liver. The two types of beads were distinguishable by differences in their surface topography. Immobilizations were performed by adsorption followed by treatment with glutaraldehyde. The immobilized-enzyme activities per unit support of all of the enzymes tested were compared with and found to be superior to the immobilized activities attainable on aminopropyl-activated glass microbeads. When enzyme was present in less than saturating amounts, the coated beads were able to remove 100% of the glucose oxidase activity initially present in the immobilization solution, with 78-87% of that activity expressed on the support surface. Bound glucose oxidase was more stable to thermal inactivation than native enzyme.

Cellulolytic Enzyme System of Acetivibrio cellulolyticus, a Newly Isolated Anaerobe

Abstract: Crude enzyme preparations from Acetivibrio cellulolyticus converted ball-milled pulp, cotton batting, filter and tissue paper, a microcrystalline cellulose, carboxymethylcellulose, cellobiose and xylan to reducing sugars. The preparations showed maximum activity between pH 5 and 6 and at a temperature between 37 and 50 °C, depending on the substrate used. The enzyme activity was fairly stable at 2 °C for 4 weeks. The saccharifying ability of the preparation was comparable to that of commercially available cellulase preparations from Aspergillus niger and Trichoderma viride.

Pyridine nucleotide levels and ratios in Aspergillus niger

Abstract: A reliable method for the extraction and assay of pyridine nucleotides (NAD, NADH, NADP, and NADPH) in filamentous fungi is presented. The method is applied to a study of the physiology of citric a...

Structural elucidation of the nigerones, four new naphthopyrones from cultures of Aspergillus niger

Abstract: The isolation and structure of four new pigments, nigerone (la), 6′-O-demethylnigerone (1b), isonigerone (2), and heminigerone (3), are described. A study of the chiroptical properties of the dimers indicates the S-configuration.

Use of the disc fermenter to examine production of citric acid by Aspergillus niger

Abstract: The effects of mode of growth on citric acid production by A. niger were studied using surface culture, shake culture and the disc fermenter. The disc fermenter enabled the effects of medium exchange with biomass retention to be examined.

Purification and immobilization of aspergillus niger beta -xylosidase

Abstract: ..beta..-Xylosidase from a commercial Aspergillus niger preparation was purified by differential ammonium sulfate precipitation and either gel permeation or cation exchange chromatography, giving 16-fold purification in 32% yield for the first technique or 27-fold purification in 19% yield for the second. Enzyme prepared by this method was immobilized to 10 different carriers, but only when it was bound to alumina with TiCl/sub 4/ and to alkylamine porous silica with glutaraldehyde were substantial efficiencies and stabilities achieved.

Changes in Preservative Sensitivity for the USP Antimicrobial Agents Effectiveness Test Micro-organisms

Abstract: Chemically defined and semi-defined media were designed for the preservative-efficacy testing micro-organisms designated by the United States Pharmacopoeia, in which the organisms went into the stationary phase of growth at an optical density (E470) of 1.0, because of depletion of a single carbon, nitrogen or phosphate source. Aspergillus niger was grown on solid media containing concentrations of these nutrients which limited the rates of mycelial development and sporulation density. The ability of the micro-organisms to survive and grow in the presence of chlorhexidine diacetate, benzalkonium chloride and thiomersal varied markedly with the nutrient-depletion of the inocula. No universal pattern of sensitivity emerged among microorganisms. Only A. niger showed little overall change in preservative sensitivity. These results highlight the need to define more adequately growth media and conditions for the production of inocula for antimicrobial challenge tests.

Influence of environmental factors on antagonism of fungi by bacteria in soil: nutrient levels.

Abstract: The addition of 0.25, 0.5, or 1.0% glucose to a soil (K) amended with either 6% kaolinite (K6K) or montmorillonite (K6M) or the adjustment of the C/N ratio of the soils from 23/1 to 10/1 with NH4NO3 eliminated the inhibition of Aspergillus niger by Serratia marcescens, regardless of whether the fungus and bacterium were inoculated into the same or separate sites in the soils. The adjustment of the C/N ratio to 15/1 or of the C/P ratio from 1,000/1 to 100/1 with KH2PO4 did not eliminate the antagonism. However, with the higher glucose and NH4NO3 amendments, S. marcescens died out in the K and K6K (but not in the K6M) soils, apparently due to reductions in pH that resulted from the increased metabolism induced by added nutrients. In soils amended with CaCO3, S. marcescens did not die out, but the inhibition of A. niger by S. marcescens or Agrobacterium radiobacter was eliminated or reduced by the addition of glucose, but not of NH4NO3, and was influenced by the clay mineralogy and pH of the soils. When NH4NO3 was added to the soils adjusted with CaCO3 to pH values above 6.0, growth of A. niger was inhibited, regardless of whether bacteria were present or not, as a result of the volatilization of NH3. Bacillus cereus and another species of Bacillus did not inhibit A. niger under any of the environmental conditions. There was a direct correlation between the degree of inhibition and the rate of glucose utilization by the various bacteria, indicating that the antagonism of A. niger by some bacteria in soil was the result primarily of a competition for carbon and that this competition was influenced by other environmental factors, such as pH and clay mineralogy.

Properties of soluble and immobilized Aspergillus niger β‐xylosidase

Abstract: Aspergillus niger ..beta..-xylosidase was characterized when in soluble form and when immobilized to alkylamine porous silica with glutaraldehyde and to alumina with titanium tetrachloride. Energies of activation averaged 13.4 kcal/mol for the soluble enzyme, 9.0 kcal/mol when immobilized to alumina, and 8.0 kcal/mol when bound to silica. The highest activity of all forms of ..beta..-xylosidase was found near pH 3. The soluble enzyme was highly stable at pH 4, where lowest rates of decay occurred, and temperatures of 65/sup 0/C and below.

Isolation and characterization of a chlorogenic acid esterase from Aspergillus niger.

Abstract: The isolation and characterization of a specific chlorogenic acid esterase is described. The enzyme activity is measured by determination of the hydrolysis product caffeic acid. The enzyme had been concentrated by means of ultrafiltration and column-chromatography. The pH- and temperature optimum were 6.5 and 45 degrees C respectively. Divalent cations were not required for the enzyme activity. As other esterases, this enzyme is inhibited by di-isopropyl-phosphorofluoridate. The Km-value is 0.70 mM chlorogenic acid, the molecule weight 240 000. The described enzyme is specific for chlorogenic acid. On the other hand a typical unspecific esterase like the pig liver esterases does not split chlorogenic acid. The isoelectric focusing reveals several isoenzymes of chlorogenase within a pI-range of 4.0-4.5.

cAMP concentration, morphological differentiation and citric acid production in Aspergillus niger

Abstract: The possibility that adenosine 3′,5′ monophosphate exerts an effect on citric acid production by Aspergillus niger by influencing pellet morphology has been investigated. The effect of pH and inoculum size on pellet formation, citric acid production, and intracellular and extracellular cAMP levels were studied. High levels of intracellular and extracellular cAMP in the later stages of the fermentation, the period of maximum citric acid formation, were associated with those treatments which gave pellets of intermediate size. The highest cAMP levels were associated with those treatments which gave the highest citric acid titre. It was concluded that high cAMP levels are principally associated with an optimum physiological state for citric acid production and that cAMP levels do not vary directly with pellet size.

Weitere Charakterisierung einer Chlorogensäure-Hydrolase aus Aspergillus niger / Further Characterization of a Chlorogenic Acid Hydrolase from Aspergillus niger

Abstract: In addition to our previous paper [1] further characteristics of the chlorogenic acid hydrolase are described. Polyacrylamide gel electrophoresis revealed only one band for the purified enzyme. Sodium dodecyl-sulfate polyacrylamide gel electrophoresis showed a molecular weight of 60 000, demonstrating four subunits of the enzyme (total molecular weight 240 000). The enzyme is stable in a pH-range of 3.0--8.5 and up to a temperature of 55 degrees C. The temperature coefficient Q10 is 1.5, the activation energy EA is 6.0 kcal/mol. The amino acid analysis and substrate specificity data are given in tables. Essential for the enzyme activity is the C=C double bound neighbouring the ester linkage. The enzyme crystallizes in prisms.

Parasexual hybridisation and citric acid production by Aspergillus niger

Abstract: In this investigation hybridisation experiments were performed with two auxotrophic mutants of Aspergillus niger. A heterozygous diploid was derived from them and it produced segregants including parental haploids and a recombinant. Their yield characters were studied.

Immobilization of microorganisms in gelled carrageenan

Abstract: Microorganisms are immobilized by mixing the microorganisms with an aqueous solution of kappacarrageenan and gelling the resultant mixture by the addition of an epihalohydrin: alkylene polyamine polymer having a mole ratio of from about 0.60:1 to 2.7:1 and a molecular weight of from 4,000 to 50,000 or by the addition of polyethyleneimine having a molecular weight of 300 to 50,000. Preferred microorganisms are Aspergillus niger and Saccharomyces cerevisiae which are respectively used to produce citric acid and ethanol.