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At least 217 records · Page 12Linked to original sources
PubMed2006

Isolation of epiphytic yeasts with potential for biocontrol of Aspergillus carbonarius and A. niger on grape.

Antagonistic yeasts were isolated from the epiphytic flora associated with grape berries cv. Negroamaro and identified at species level using molecular methods. A total of 144 yeast isolates were tested in a preliminary screening on agar to select isolates showing a killer activity against Aspergillus carbonarius and A. niger, the main species responsible for the accumulation of ochratoxin A in grape. Twenty-eight yeast isolates were selected for their inhibitory effects on the above fungal species and assayed by an in vitro nutritional competition test for their antagonistic capacity towards three selected ochratoxigenic strains. Six yeast isolates belonging to five species, namely 2 isolates of Issatchenkia orientalis and one each of Metschnikowia pulcherrima, Kluyveromyces thermotolerans, Issatchenkia terricola and Candida incommunis, were finally selected and screened on wounded grape berries for their ability to inhibit infection by ochratoxigenic moulds. With the exception of the K. thermotolerans isolate, when inoculated at 10(9) CFU/wound, the other five challenger yeasts reduced the A. carbonarius and A. niger colonization on grape berry (P<0.05). In particular, the best antagonistic activity was shown by the two I. orientalis isolates. Results suggest that antagonist yeasts with the potential to control A. carbonarius and A. niger on grape can be found among the microflora associated with the berries.

Antibiosis↗
PubMed2006

Digestion of DNA regions to discriminate ochratoxigenic and non-ochratoxigenic strains in the Aspergillus niger aggregate.

Aspergillus strains belonging to the Aspergillus niger aggregate, either isolated from Italian grapes or received from public collections, were analysed in order to discriminate between the ochratoxin A (OTA) producing and the non-producing strains by means of the analysis of Internal Transcribed Spacers (ITS), Intergenic Spacers (IGS) and of a beta-tubulin gene portion. A. niger and Aspergillus awamori were identified observing the macro- and microscopic features of the colonies and the strains ochratoxigenicity was evaluated through Thin Layer Chromatography and/or High Performance Liquid Chromatography. PCR amplification of ITS, IGS and beta-tubulin gene portion produced 600, 440 and 550 bp amplicons, respectively, in all the analysed strains. The digestion of the IGS amplicon with Hinf I and of the other two amplicons with Rsa I, revealed one main profile type ("T-C-C") associated with the A. niger aggregate strains which lack the ability to produce OTA.

Aspergillus niger↗
PubMed2006

Effect of temperature and water activity on growth and ochratoxin A production by Australian Aspergillus carbonarius and A. niger isolates on a simulated grape juice medium.

The effect of water activity (0.92, 0.95, 0.965 and 0.98) and temperature (15 degrees C, 25 degrees C, 30 degrees C and 35 degrees C) on growth rate and ochratoxin A (OA) production by five strains of Aspergillus carbonarius and two strains of A. niger isolated from Australian vineyards was characterised on a synthetic grape juice medium. Maximum growth for A. carbonarius occurred at ca 0.965 aw and 30 degrees C, and for A. niger, at ca 0.98 aw and 35 degrees C. The optimum temperature for OA production was 15 degrees C and little was produced above 25 degrees C. The optimum aw for toxin production was 0.95-0.98 for A. carbonarius and 0.95 for A. niger. Toxin was produced in young colonies after and, typically, did not continue to accumulate the entire surface area of the plate was colonised. Rather, the amount decreased as colonies aged. Trends for growth and OA production were similar among Australian isolates and those from European grapes, as reported in the literature.

Aspergillus↗
PubMed2004

A drop of intracellular pH stimulates citric acid accumulation by some strains of Aspergillus niger.

By comparing kinetic parameters of plasma membrane proton pumps from two Aspergillus niger strains, significant differences in specific activities were observed. In low citric acid producing A158 strain the H+ -ATPase activity was about four-fold higher than in a high yielding A60 strain. Previously pH homeostasis was reported in A158 strain while in A60 strain spontaneous drop of intracellular pH was observed. During the growth in the medium with ammonium ions more rapid drop of extracellular pH was recorded with A158 strain and not so fast proton accumulation in the medium with A60 strain, indicating that proton pumps from later strain perhaps can not extrude all the protons that are released in the cytosol after the assimilation of ammonium ions. Vanadium ions were found to be potent inhibitors of both H+ -ATPases. By adding sodium vanadate in millimolar concentrations to the chemically defined medium that induces citric acid accumulation by A. niger, reduced pHi and increased rate of acid production was observed in A158 strain while in A60 strain intracellular pH decreased below 6.5 and concomitantly citric acid overflow was suppressed. The presented results suggest that one of the mechanisms stimulating citric acid accumulation by A. niger could be also a slight cytoplasmic acidification.

Aspergillus niger↗
PubMed1997

Action patterns and mapping of the substrate-binding regions of endo-(1-->5)-alpha-L-arabinanases from Aspergillus niger and Aspergillus aculeatus.

The substrate binding sites of endo-(1-->5)-alpha-L-arabinanases (EC 3.2.1.99) from Aspergillus niger and Aspergillus aculeatus were investigated using reduced and regular (1-->5)-alpha-L-arabino-oligosaccharides and high performance anion exchange chromatographic analysis. Calculation of bond cleavage frequencies and kcat/K(m) parameters for these substrates enabled the determination of the number of arabinofuranosyl binding subsites and the estimation of the binding affinities of each subsite. The A. aculeatus endo-arabinanase has six subsites arranged symmetrically around the catalytic site, while the A. niger endo-arabinanase has five subsites; two from the catalytic site towards the non-reducing end of the bound substrate and three toward the reducing end. The two subsites directly adjacent to the catalytic sites in both the A. niger and A. aculeatus endo-arabinanase have near-zero net free energy of binding. These results are unlike most glycopyranosyl endo-hydrolases studied which have net negative (unfavourable) energies of interaction at these two subsites, and may be related to the greater conformational flexibility of arabinofuranosyl residues than glycopyranosyl residues. The complete subsite maps are also rationalized with regard to the observed action patterns of these enzymes on linear (1-->5)-alpha-L-arabinan.

Aspergillus↗
PubMed2000

Characterization of a novel endopolygalacturonase from Aspergillus niger with unique kinetic properties.

We isolated and characterized a new type of endopolygalacturonase (PG)-encoding gene, pgaD, from Aspergillus niger. The primary structure of PGD differs from that of other A. niger PGs by a 136 amino acid residues long N-terminal extension. Biochemical analysis demonstrated extreme processive behavior of the enzyme on oligomers longer than five galacturonate units. Furthermore, PGD is the only A. niger PG capable of hydrolyzing di-galacturonate. It is tentatively concluded that the enzyme is composed of four subsites. The physiological role of PGD is discussed.

Aspergillus niger↗
PubMed1997

Equine pulmonary mycosis due to Aspergillus niger and Rhizopus stolonifer.

Invasive pulmonary mycosis caused by Aspergillus niger and Rhizopus stolonifer is reported in a 2-year-old horse, one of three that died after being housed in a disused, uncleaned stable. Lesions were characterized by thrombosis of the blood vessels with haemorrhage and tissue necrosis. Fungal hyphae were observed both in thrombosed vessels and in adjacent necrotic tissue. In culture media inoculated with lung samples and samples from the bedding hay, two types of colony were recorded and identified as A. niger and R. stolonifer. This study is the first description of equine pulmonary mucormycosis and of A. niger as an aetiological agent in the horse.

Animals↗
PubMed2000

Biotransformation of geraniol, nerol and citral by sporulated surface cultures of Aspergillus niger and Penicillium sp.

The biotransformation of geraniol, nerol and citral by Aspergillus niger was studied. A comparison was made between submerged liquid, sporulated surface cultures and spore suspensions. This bioconversion was also carried out with surface cultures of Penicillium sp. The main bioconversion products obtained from geraniol and nerol by liquid cultures of A. niger were linalool and alpha-terpineol. Linalool, alpha-terpineol and limonene were the main products obtained from nerol and citral by sporulated surface cultures, whereas geraniol was converted predominantly to linalool, also resulting in higher yields. Bioconversion of nerol with Penicillium chrysogenum yielded mainly alpha-terpineol and some unidentified compounds. With P. rugulosum the major bioconversion product from nerol and citral was linalool. The bioconversion of nerol to alpha-terpineol and linalool by spore suspensions of A. niger was also investigated. Finally the biotransformation with sporulated surface cultures was also monitored by solid phase microextraction (SPME). It was found that SPME is a very fast and efficient screening technique for biotransformation experiments.

Acyclic Monoterpenes↗
PubMed1977

Relation of lipids to the action of streptomycin on Bacillus subtilis and Escherichia coli and griseofulvin and fungizone on Aspergillus niger.

An attempt was made to reveal the relation between the lipid content and components of B. subtilis and E. coli and the action of streptomycin, and those of A. niger and the action of griseofulvin and fungizone (Amphotericin B). Total lipids were extracted in CO2 atmosphere, dried, and weighed. Lipid components were analyzed by thin-layer chromatography. Complements to the growth medium of A. niger with extracted total lipids and phospholipids were made to verify the obtained results. It has been found that the action of streptomycin and griseofulvin was not correlated with lipids. On the other hand, fungizone action was manifested by the decrease in total lipids, free sterols, sterol esters, and triglycerides. Supplementation studies gave evidence of the role of total lipids and phospholipids in protecting A. niger cells against fungizone. Supplementation of 1 g of phospholipid per litre medium raised the M.I.D. of fungizone from 2.5 up to 25 microgram/ml. It was suggested to keep the fat level controlled at a minimum if it is required to increase fungizone activity.

Amphotericin B↗
PubMed1998

Characterization of galactosidases from Aspergillus niger: purification of a novel alpha-galactosidase activity.

An enzyme with beta-galactosidase activity and three proteins exhibiting alpha-galactosidase activity were purified from a culture filtrate of Aspergillus niger grown on arabinoxylan. beta-galactosidase, optimally active at pH 4 and 60-65 degrees C, was active against p-nitrophenyl-beta-D-galactopyranoside, lactose, and pectic galactan. It was not able to release galactose from sugar beet pectin or lemon pectin. Its action on pectic galactan was increased by the presence of beta-galactanase. The three forms of alpha-galactosidase activity that showed different molecular masses and pIs were found to have the same mass after deglycosylation with N-glycanase F and to be the same protein based on their N-terminal amino acid sequence data. The purified alpha-galactosidase was shown to be different from alpha-galactosidase A from A. niger. This confirmed the existence of at least two different alpha-galactosidases in A. niger. alpha-Galactosidase, optimally active at pH 4.5 and 50-55 degrees C, was active toward p-nitrophenyl-alpha-D-galactopyranoside, melibiose, raffinose, stachyose, and locust bean gum, on which substrate it exhibited synergism with beta-mannanase.

Amino Acid Sequence↗
PubMed2003

Polymerase chain reaction aids in the diagnosis of an unusual case of Aspergillus niger endocarditis in a patient with acute myeloid leukaemia.

Endocarditis secondary to Aspergillus niger has not been described in a leukaemic patient. We describe a case of A. niger endocarditis in a patient with acute myeloid leukaemia and refractory fever. The microbiological cause of his endocarditis was initially misdiagnosed because he fulfilled the Duke criteria for enterococcal endocarditis. A polymerase chain reaction test utilizing pan-fungal primers detected a product from an Aspergillus sp. The DNA was subsequently sequenced and was found to have 100% homology with A. niger. A postmortem revealed fungal endocarditis secondary to disseminated aspergillosis, without evidence of bacterial endocarditis. The patient was found to have a lung aspergilloma that was possibly occupationally acquired, and may have been long standing.

Aspergillosis↗
PubMed1998

Effect of gamma irradiation on the production of cell wall degrading enzymes by Aspergillus niger.

Fungi occurring in Egyptian fruits in the City of Qena were studied. Results from the examination of 25 replicated samples of plums, pears and apples are reported. Examinations were carried out by direct plating after surface disinfection in a 0.5% (w/v) calcium hypochlorite solution on Czapek's-Dox agar. The dominant fungus found in the three types of fruit was Aspergillus niger, which was present in 88% of plum samples, 80% of pear samples and all of the apple samples. The lowest dose of gamma irradiation (1 MCi for 10 min) enhanced the three isolates of A. niger investigated to produce more biomass and polygalactronase, pectinmethylglacturonase, cellulase and protease. The higher doses (1 MCi for 20 and 30 min) were inhibitory to the growth of A. niger.

Aspergillus niger↗
PubMed1996

Secretion of active human mucus proteinase inhibitor by Aspergillus niger after KEX2-like processing of a glucoamylase-inhibitor fusion protein.

We report the production of human mucus proteinase inhibitor (MPI) by the filamentous fungus Aspergillus niger to test the ability of this host organism to secrete low molecular weight, highly disulfide-bonded proteins in biologically active conformation. Fungal transformants have been obtained with an expression cassette consisting of a chimeric gene founded on a mpi cDNA, encoding mature MPI, fused in frame to sequences encoding A. niger glucoamylase (glaA), separated by a KEX2-like processing sequence. Expression of the glucoamylase fusion gene in these transformants resulted in secretion of MPI into the growth medium with yields up to 3 mg 1-1. N-terminal sequence analysis of the purified inhibitor confirmed that the glucoamylase-MPI fusion protein was correctly processed to mature MPI by a KEX2-type endopeptidase present in A. niger. Furthermore, recombinant MPI retains full inhibitory activity against chymotrypsin and leukocyte elastase indicating that the protein was folded properly.

Amino Acid Sequence↗
PubMed2000

Measurement of intracellular (compartmental) pH by 31P NMR in Aspergillus niger.

31P nuclear magnetic resonance (31P NMR) was used to monitor cytoplasmic and vacuolar pH values in the filamentous fungus Aspergillus niger. To obtain a homogeneous cell sample and to be able to perform long term in vivo NMR measurements A. niger mycelium was kept in a setup that allows perfusion of the cell plug within the NMR tube. Mycelial samples, however, became rapidly clogged during perfusion leading to (partial) anaerobiosis of the plug with subsequent acidification of the cytoplasm. As a result, only short-term NMR measurements (5-10 min) were possible using free mycelium. To increase and to prolong perfusion, A. niger was immobilized in Ca(2+)-alginate beads. Deteriorated spectra recorded under hypoxia could be completely restored in the presence of oxygen. With this system perfusion in the presence of citrate could be maintained for at least 18 h at much higher rates (15 ml min-1 compared with 4 ml min-1 for free mycelium). During this period 31P NMR spectra were highly invariable, indicating approximate steady-state intracellular conditions during long term measurements. Perfusion in the presence of glucose resulted in complete depletion of the vacuolar inorganic phosphate pool within 45 min and yielded a higher pH gradient over the tonoplast than when citrate was used (delta pH = 1.6 and 1.4, respectively).

Alginates↗
PubMed2003

Interpretation of intraspecific variability in mtDNAs of Aspergillus niger strains and rearrangement of their mtDNAs following mitochondrial transmissions.

Physical and functional maps of mitochondrial DNAs of Aspergillus niger strains representing different mitochondrial DNA RFLP patterns were constructed and compared. In spite of the high similarity in the organisation of mitochondrial DNAs among examined strains, differences could be easily recognised by applying molecular markers, such as the different intron content of the cox1 genes, the sequence of the intergenic regions between the Met- and His-tRNA genes and downstream of the tRNA-Gly gene. Intraspecific mitochondrial transfers between the heterokaryon incompatible mitochondrial oligomycin-resistant A. niger strain, as the donor, and other A. niger-sensitive strains bearing different RFLP patterns resulted in oligomycin-resistant progeny possessing either rearranged or unchanged donor mitochondrial DNA and recipient nuclei. Since the intergenic marker sequences of mitochondrial DNAs turned out to be identical in the donor and the progeny, it can be assumed that the oligomycin-resistant progeny inherit the mitochondrial DNA of the donor strain; this may either remain unchanged or may be modified by a mobile intron of the cox1 gene of the recipient mitochondria.

Aspergillus niger↗
PubMed1997

Solubilisation of some naturally occurring metal-bearing minerals, limescale and lead phosphate by Aspergillus niger.

The ability of the soil fungus Aspergillus niger to tolerate and solubilise seven naturally occurring metal-bearing minerals, limescale and lead phosphate was investigated. A. niger was able to solubilise four of the test insoluble compounds when incorporated into solid medium: cuprite (CuO2), galena (PbS), rhodochrosite (Mn(CO3)x) and limescale (CaCO3). A. niger was able to grow on all concentrations of all the test compounds, whether solubilisation occurred or not, with no reduction in growth rate from the control. In some cases, stimulation of growth occurred, most marked with the phosphate-containing mineral, apatite. Precipitation of insoluble copper and manganese oxalate crystals under colonies growing on agar amended with cuprite and rhodochrosite was observed after 1-2 days growth at 25 degrees C. This process of oxalate formation represents a reduction in bioavailability of toxic cations, and could represent an important means of toxic metal immobilisation of physiological and environmental significance.

Agar↗
PubMed1997

Isolation and characterisation of a novel stress-inducible PDI-family gene from Aspergillus niger.

Current strategies to improve the secretion of heterologous proteins in Aspergillus niger include the manipulation of chaperones and foldases specific to the endoplasmic reticulum (ER). A family of ER-specific proteins which share active-site homology wit protein disulfide isomerase (PDI) has been identified from other systems, many of which are inducible by agents which cause malfolding of proteins in the ER. Here we report identification of tigA from Aspergillus niger and erp38 from Neurospora crassa, two novel members of the PDI superfamily of proteins. TIGA and ERp38 show 66% identity at the amino acid level and are putative ER proteins. Both proteins show tandemly linked thiol-oxidoreductase domains followed by a functionally uncharacterised C-terminal domain. The most distal active site in TIGA is created by excision of a 66-bp intron. Although no Unfolded Protein Response elements can be seen in the tigA promoter, sequence homology has identified associated with protein trafficking (ERPTRE) in a gene encoding the related mammalian protein, ERp72, as well as a second motif conserved amongst the glucose-related protein family. Southern and dot blot analysis indicate that the tigA gene is present in single copy. Both the A. niger and N. crassa proteins show homology with a stress-inducible alfalfa, G1. Transcription of tigA is induced 2-3-fold after treatment with tunicamycin, an inhibitor of N-linked glycosylation. Strains overexpressing a heterologous protein show no increased tigA mRNA levels.

Amino Acid Sequence↗
PubMed2002

Dye biosorption sites in Aspergillus niger.

Aspergillus niger is capable of removing dyes from an aqueous solution. In the study, the roles played by three major functional groups: carboxyl, amino and phosphate, and the lipid fraction in the biomass of A. niger in biosorption of four dyes, Basic Blue 9, Acid Blue 29, Congo Red and Disperse Red 1, were investigated. These functional groups in A. niger were chemically modified individually to determine their contribution to the biosorption of dyes. It was found that biosorption of dyes was influenced by the functional groups in the fungal biomass and the chemical structure of the dyes.

Absorption↗