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Showing papers on "Aspergillus niger published in 1996"


Journal ArticleDOI
TL;DR: In this article, Aspergillus niger grows in the presence of up to 10% (w/v) of fly ash in the medium and produces gluconate, whereas in its absence citrate was produced.
Abstract: Biological leaching of fly ash from municipal waste incineration by Aspergillus niger was examined in batch cultures and compared with chemical leaching. A. niger grew in the presence of up to 10% (w/v) of fly ash in the medium. In the presence of fly ash A. niger produced gluconate, whereas in its absence citrate was produced. Variation of the fly ash concentration in the growth medium (one-step process) resulted in different amounts of solubilized metals. A total of 3% (w/v) fly ash generally gave maximum extraction yields (in percent of the amount applied). In a two-step process A. niger first was cultivated in the growth medium, and subsequently the microbiologically produced citric acid was used as the leaching agent. At 6% (w/v) fly ash, the amounts of leached metals (leaching for 1 day) were 81% of Cd, 66% of Zn, 57% of Cu, 52% of Pb, 32% of Mn, 27% of Al, and less than 10% of Cr, Fe, and Ni, respectively. Chemical leaching with commercial citric acid of equal molarity was only slightly higher than...

245 citations


Journal ArticleDOI
TL;DR: The monoclonal antibody-based ELISA technique was successfully used to screen for low levels of ochratoxin A in the black Aspergilli without concentrating the culture filtrates, confirmed by TLC and HPLC analysis and chemical derivatization.
Abstract: One hundred and fifty-seven strains belonging to Aspergillus section Nigri were tested for ochratoxin A production using three different methods: a relatively new immunochemical method based on an enzyme-linked immunosorbent assay (ELISA), thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC). The monoclonal antibody-based ELISA technique was successfully used to screen for low levels of ochratoxin A in the black Aspergilli without concentrating the culture filtrates. The results were confirmed by TLC and HPLC analysis and chemical derivatization. These latter methods required concentrated filtrates. Ochratoxin A was detected in the culture filtrates of five of the 12 A. carbonarius strains, none of the 45 A.japonicus strains and three of the 100 isolates in the A. niger aggregate (A. foetidus, A. awamori and A. niger).

219 citations


Journal ArticleDOI
TL;DR: A two-step bioconversion process of ferulic acid to vanillin was elaborated combining two filamentous fungi, Aspergillus niger and Pycnoporus cinnabarinus, successfully produced and sequential additions of precursors were performed to improve the yields.

207 citations


Journal ArticleDOI
TL;DR: The crystal structure of endo-1,4-beta-xylanase I from Aspergillus niger has been solved by molecular replacement and was refined to 2.4 A resolution, which is of particular commercial interest because of its low pH optimum.

180 citations


Journal ArticleDOI
TL;DR: A biocontrol rhizobacterial strain of Bacillus subtilis AF 1 grown for 6 h was coinoculated with Aspergillus niger at different time intervals and microscopic observations revealed adherence of bacterial cells to the fungal mycelium.
Abstract: A biocontrol rhizobacterial strain of Bacillus subtilis AF 1 grown for 6 h was coinoculated with Aspergillus niger at different time intervals and microscopic observations revealed adherence of bac...

110 citations


Journal ArticleDOI
TL;DR: PME I was able to remove 75-85% of the methyl groups in highly methylated pectin, and it did not remove acetyl groups from acetylated polysaccharides, which demonstrates that PME I acts in synergy with polygalacturonases in the degradation of plant cell wall pECTin.
Abstract: Seventeen full-length cDNAs encoding pectin methyl esterase I (PME I) have been isolated from the filamentous fungus Aspergillus aculeatus by expression cloning in yeast. Yeast colonies expressing functional PME I were identified on agar plates containing highly esterified pectin, and a cDNA encoding PME I was isolated. The deduced amino acid sequence of PME I is highly similar (74% identity) to the PME from Aspergillus niger. A full-length cDNA encoding PME I was cloned into an Aspergillus expression vector and transformed into Aspergillus oryzae for heterologous expression, purification and characterization of the recombinant enzyme. The recombinant PME I had a molecular mass of 36.2 kDa, an isoelectric point of pH 3.8, a pH optimum of 4.6 and a temperature optimum of 45 degrees C. The authentic PME I was purified from A. aculeatus culture supernatant and subjected to amino acid sequencing. The peptide sequences covered 138 amino acid residues and were in complete agreement with the deduced PME I sequence. Both recombinant and authentic PME I were glycosylated, but the composition of the glycan moieties was different. PME I was able to remove 75-85% of the methyl groups in highly methylated pectin, and it did not remove acetyl groups from acetylated polysaccharides. When the enzyme was added together with polygalacturonases to pectin, a rapid depolymerization was observed. By comparison, polygalacturonases alone showed a very limited degradation of the methylated substrate. This demonstrates that PME I acts in synergy with polygalacturonases in the degradation of plant cell wall pectin.

106 citations


Journal ArticleDOI
TL;DR: The activity of the pure enzyme was inhibited by more than 99% after treatment with the serine‐specific protease inhibitor aminoethylbenzenesulphonylfluoride (1 mM) for 12 h, and was capable of releasing ferulic acid from sugar beet pulp.
Abstract: An inducible esterase has been isolated from a liquid culture of Aspergillus niger grown on sugar-beet pulp. The enzyme was active on methyl esters of cinnamic acids, caffeic > p-coumaric > ferulic, and is therefore termed a cinnamoyl esterase. The enzyme was not active on methyl sinapinate, a good substrate for ferulic acid esterase III, which was purified previously from A. niger [Faulds and Williamson (1994) Microbiology 140, 779-787]. With methyl caffeate as substrate the enzyme had temperature and pH optima of 50 degrees C and 6.0 respectively, and a specific activity of 96.9 units per mg of protein. The purified protein (native molecular mass 145 000 Da) gave a single heavily stained band on SDS/PAGE, suggesting the protein was a dimer, and seemed to be heavily glycosylated. Isoelectric focusing gave a single band corresponding to a pl of 4.80. The pure enzyme was free of other carbohydrase activities. The activity of the pure enzyme was inhibited by more than 99% after treatment with the serine-specific protease inhibitor aminoethylbenzenesulphonylfluoride (1 mM) for 12 h. The enzyme was capable of releasing ferulic acid from sugar beet pulp.

98 citations


Journal ArticleDOI
TL;DR: The data suggest that intracellular protein degradation is the most likely explanation for the low levels of secreted human interleukin 6.
Abstract: A study was carried out to obtain more insight into the parameters that determine the secretion of heterologous proteins from filamentous fungi. A strategy was chosen in which the mRNA levels and protein levels of a number of heterologous genes of different origins were compared. All genes were under control of the Aspergillus awamori 1,4-β-endoxylanase A (exlA) expression signals and were integrated in a single copy at the A. awamori pyrG locus. A Northern (RNA) analysis showed that large differences occurred in the steady-state mRNA levels obtained with the various genes; those levels varied from high values for genes of fungal origin (A. awamori 1,4-β- endoxylanase A, Aspergillus niger glucoamylase, and Thermomyces lanuginosa lipase) to low values for genes of nonfungal origin (human interleukin 6 and Cyamopsis tetragonoloba [guar] α-galactosidase). With the C. tetragonoloba α-galactosidase wild-type gene full-length mRNA was even undetectable. Surprisingly, small amounts of full-length mRNA could be detected when a C. tetragonoloba α-galactosidase gene with an optimized Saccharomyces cerevisiae codon preference was expressed. In all cases except human interleukin 6, the protein levels corresponded to the amounts expected on basis of the mRNA levels. For human interleukin 6, very low protein levels were observed, whereas relatively high steady-state mRNA levels were obtained. Our data suggest that intracellular protein degradation is the most likely explanation for the low levels of secreted human interleukin 6.

95 citations


Journal ArticleDOI
TL;DR: Complementary and genomic DNAs encoding an acid-stable α-amylase (asAA) were cloned from Aspergillus kawachii IFO4308 and their nucleotide sequences were determined.

94 citations


Journal ArticleDOI
TL;DR: The calculated molecular mass and the hydrolytic properties of AGLI indicate that it corresponds to the α-galactosidase previously purified from T. reesei, and the deduced amino acid sequences of A GLI and AGLIII showed similarity with the β-mannosidases of plant, animal, yeast and filamentous fungal origin.
Abstract: Three α-galactosidase genes, agl1, agl2 and agl3, were isolated from a cDNA expression library of Trichoderma reesei RutC-30 constructed in the yeast Saccharomyces cerevislae by screening the library on plates containing the substrate 5-bromo-4-chloro-3-indolyl-α-D-galactopyranoside. The genes agll, agl2 and agl3 encode 444, 746 and 624 amino acids, respectively, including the signal sequences. The deduced amino acid sequences of AGLI and AGLIII showed similarity with the α-galactosidases of plant, animal, yeast and filamentous fungal origin classified into family 27 of glycosyl hydrolases whereas the deduced amino acid sequence of AGLIII showed similarity with the bacterial α-galactosidases of family 36. The enzymes produced by yeast were analysed for enzymatic activity against different substrates. AGLI, AGLII and AGLIII were able to hydrolyse the synthetic substrate p-nitrophenyl-α-d-galactopyran-oside and the small galactose-containing oligosaccharides, melibiose and raffinose. They liberated galac-tose from polymeric galacto(gluco)mannan with different efficiencies. The action of AGLI towards polymeric substrates was enhanced by the presence of the endo-l,4-β-mannanase of T. reesei. AGLII and AGLIII showed synergy in galacto(gluco)mannan hydrolysis with the endo-1,4-β-mannanase of T. reesei and a β-mannosidase of Aspergillus niger. The calculated molecular mass and the hydrolytic properties of AGLI indicate that it corresponds to the α-galactosidase previously purified from T. reesei.

90 citations


Journal ArticleDOI
TL;DR: Feruloylated arabinans in SBP are readily available for hydrolysis by arabinan‐degrading enzymes, whereas feruloylation galactans are not available for HydrolysisBy galactan‐ Degrading enzyme.
Abstract: Aspergillus niger cinnamoyl esterase (CinnAE) is shown to be active towards a wide range of feruloylated oligosaccharides derived from sugar-beet pulp (SBP) The esterase hydrolysed ferulic acid ester-linked to either C-2 of arabinose or C-6 of galactose residues, and demonstrated the highest activity towards the feruloylated arabinose trisaccharide However, CinnAE was able to release only 088% of total alkali-extractable ferulic acid from SBP in 24 h when acting alone To determine whether cell-wall-degrading enzymes could increase the release of ferulic acid by CinnAE, SBP was incubated with various carbohydrases [cellulase, polygalacturonase, endo-arabinanase, alpha-L-arabinofuranosidase, endo-(1,4-beta-D-galactanase, beta-D-galactosidase] These were added alone and in pairs, both in the presence and absence of CinnAE We showed that all the carbohydrases tested were free of esterase activity When individual carbohydrases were incubated with SBP, whether in the presence or absence of CinnAE, less than 1% of the feruloyl groups were released When incubated with a mixture of endo-arabinanase and alpha-L-arabinofuranosidase, the esterase was able to release 14 times more of the alkali-extractable ferulic acid present in the whole pulp as free acid than CinnAE alone Ferulic acid is linked either to L-arabinose or D-galactose in SBP, but no corresponding increase in ferulic acid release was detected when SBP was incubated with CinnAE plus endo-(1,4)-beta-D-galactanase and beta-D-galactosidase (both from A niger) Hence feruloylated arabinans in SBP are readily available for hydrolysis by arabinan-degrading enzymes, whereas feruloylated galactans are not available for hydrolysis by galactan-degrading enzymes

Journal ArticleDOI
TL;DR: Observations concerning the effect of gluconolactone and the levels of glucose-6-phosphate isomerase upon calcium carbonate induction suggested that the enhancement of glucose oxidase biosynthesis by calcium Carbonate was accompanied by a metabolic shift from glycolysis to the pentose phosphate pathway.
Abstract: A new glucose oxidase from Aspergillus niger was isolated and characterized. The enzyme showed different kinetic and stability characteristics when compared to a commercially available batch of A. niger glucose oxidase. The gene encoding the new glucose oxidase was isolated and DNA sequence analysis of the coding region showed 80% identity to the sequence of a glucose oxidase gene previously published. However, the similarity of the non-coding sequences up- and downstream of the open reading frame was much less, showing only 66% and 50% identity respectively. Despite the low degree of similarity between the promotor region of the new gene and the previously published one, the new glucose oxidase was likewise induced by calcium carbonate. In addition, we showed that this induction occurred on the transcriptional level. Observations concerning the effect of gluconolactone and the levels of glucose-6 phosphate isomerase upon calcium carbonate induction suggested that the enhancement of glucose oxidase biosynthesis by calcium carbonate was accompanied by a metabolic shift from glycolysis to the pentose phosphate pathway.

Journal ArticleDOI
TL;DR: The reduction in pectinase production at 350 and 450 g/l initial glucose concentration was due neither to repression of the synthesis of the enzyme nor to the glucose consumption rate of the strain but due to a drastic drop in pH of the medium.
Abstract: Exopectinase (exo-p) and endopectinase (endo-p) production by Aspergillus niger CH4 in solid state culture was studied at initial glucose concentrations of 100, 250, 350 and 450 g/l. The highest activity of exo-p (35 U/g) was produced at 72 and 120 h in the medium containing 100 and 250 g glucose/l, respectively. The maximum endo-p activity (9 U/g) was produced at 72 h in the medium with 250 g glucose/l. The reduction in pectinase production at 350 and 450 g/l initial glucose concentration was due neither to repression of the synthesis of the enzyme nor to the glucose consumption rate of the strain but due to a drastic drop in pH of the medium.

Journal ArticleDOI
TL;DR: Combined introduction of both the filamentous and arbuscular fungi led to improved plant growth when degraded organic matter supplemented or unsupplemented with Po t' was used.

Journal ArticleDOI
TL;DR: The measured levels were, in general, similar to values published previously and obtained by various other methods, and the advantage of the procedure described here is that all metabolites can be assayed in a single extract.

Journal ArticleDOI
TL;DR: The data suggest that the thermotolerant A. fumigatus Cu,Zn SOD would be more effective in such a protective system than, for example, the equivalent enzyme from the more rarely pathogenic A. nidulans and A. terreus.
Abstract: Cu,Zn superoxide dismutases (SODs) have been purified to homogeneity from Aspergillus flavus and A. niger, which are significant causative agents of aspergillosis, and from A. nidulans and A. terreus, which are much rarer causative agents of disease, using a combination of isoelectric focusing and gel filtration fast protein liquid chromatography. The purified enzymes have been compared with the previously described SOD from the most important pathogen in the genus, A. fumigatus (M. D. Holdom, R. J. Hay, and A. J. Hamilton, Free Radical Res. 22:519-531, 1995). The N-terminal amino acid sequences of the four newly purified enzymes were almost identical and demonstrated homology to known Cu,Zn SODs from a range of organisms including that from the previously described SOD from A. fumigatus. SOD activity was detectable in the culture filtrates of all species, and intracellular Cu,Zn SOD activity as a proportion of total protein was highest in early-log-phase cultures. The specific activities of the purified enzymes were similar, and all four of the newly described enzymes were inhibited by potassium cyanide and diethyldithiocarbamate, known Cu,Zn SOD inhibitors. Sodium azide and o-phenanthroline demonstrated inhibition at concentrations from 5 to 30 mM, and EDTA also exhibited a varying degree of inhibition of SOD activity. However, there were differences in the nonreduced molecular masses, the reduced molecular masses, and the isoelectric points of the four newly described SODs and the A. fumigatus enzyme; these varied from 55 to 123 kDa, 17.5 to 19.5 kDa, and 5.0 to 5.9, respectively. Of particular note was the observation that the A. fumigatus enzyme was thermostable compared with the SODs from the other species; in addition, the A.fiumigatus enzyme retained all of its activity at 37 degrees C relative to 20 degrees C, whereas the SODs of A. nidulans and A. terreus lost significant activity at the higher temperature. Aspergillus Cu,Zn SOD plays a hypothetical role in the avoidance of oxidative killing mechanisms, and our data suggest that the thermotolerant A. fumigatus Cu,Zn SOD would be more effective in such a protective system than, for example, the equivalent enzyme from the more rarely pathogenic A. nidulans.

Journal ArticleDOI
TL;DR: The results demonstrate that the initial steps of the secretory pathway are fast and that the excretion of the enzyme into the culture fluid was most likely delayed due to retention by the cell wall.
Abstract: The kinetics of glucose oxidase (GOD) excretion by recombinant Aspergillus niger NRRL-3 (GOD3-18) were investigated using enzymatic activity measurements as well as gel electrophoresis techniques. The majority of GOD was produced during rapid growth in the first phase of the cultivation. The high excretion rate during this phase did not prevent the endocellular accumulation of GOD up to 40% of the total soluble cell protein demonstrating that the production rate exceeded the excretion rate of the enzyme into the culture medium. During the second phase of the cultivation, excretion of GOD occurred at a slower rate, although the majority of GOD produced during the first phase was excreted during the second phase of the cultivation. At the end, about 90% of the total GOD produced was recovered from the culture medium. Two-dimensional gel electrophoresis provided evidence that endo- and exocellular GOD were indistinguishable, revealing identical posttranslational modifications (e.g., signal sequence cleavage, glycosylation pattern). The results demonstrate that the initial steps of the secretory pathway are fast and that the excretion of the enzyme into the culture fluid was most likely delayed due to retention by the cell wall.

Journal ArticleDOI
TL;DR: It is concluded that the low-affinity glucose transporter takes part in the mechanism by which Aspergillus niger responds to high extracellular glucose concentrations leading to citric acid accumulation.
Abstract: The filamentous fungusAspergillus niger accumulates large levels of citric acid in the medium when grown under conditions favouring a high rate of sugar catabolism. With the aim of understanding the mechanisms involved in this process we investigated glucose transport in this fungus. To this end a medium was designed that enables growth of the fungus into a fine, hairy filamentous mycelium, suitable for transport studies. It was found thatA. niger contains a single, high-affinity glucose transporter when grown on a low (1% w/v) glucose concentration, but forms an additional low-affinity transporter when grown on a high (15% w/v) glucose concentration. Both glucose transporters exhibit decreased activities at low pH and are inhibited by citric acid. However, the activity of the low-affinity transporter is much less affected by these conditions. Two 2-deoxyglucose-resistant (dgr) mutants ofA. niger, which produce citric acid at a much lower rate than the parent strain, are impaired in the formation of the low-affinity transporter, but form the high-affinity transporter with higher activities. We conclude that the low-affinity glucose transporter takes part in the mechanism by whichA. niger responds to high extracellular glucose concentrations leading to citric acid accumulation.

Journal ArticleDOI
TL;DR: Simultaneous saccharification and fermentation of Jerusalem artichoke tubers were conducted batchwise at 30°C using Aspergillus niger 817 and Saccharomyces cerevisiae 1200 to obtain Ethanol concentrations obtained.

Journal ArticleDOI
TL;DR: 1H‐NMR analysis of the action of endo‐(1 → 5)‐α‐l‐arabinanases from As pergillus niger and Aspergillus aculeatus showed that both hydrolyze linear arabinan with inversion of configuration, and may therefore act via a single displacement mechanism, consistent with the A. niger enzyme's classification in glycosyl hydrolase family 43.

Journal ArticleDOI
TL;DR: Three filamentous fungi were examined for the ability to biotransform phenanthrene to oxidative (phase I) and conjugative (phase II) metabolites and produced the glucose conjugates 1-phenanthryl β-d-glucopyranoside and 2-hydroxy-1-phenanthrenetrans-9,10-dihydrodiol, a novel metabolite.
Abstract: Three filamentous fungi were examined for the ability to biotransform phenanthrene to oxidative (phase I) and conjugative (phase II) metabolites. Phenanthrene metabolites were purified by high-performance liquid chromatography (HPLC) and identified by UV/visible absorption, mass, and1H NMR spectra.Aspergillus niger ATCC 6275,Syncephalastrum racemosum UT-70, andCunninghamella elegans ATCC 9245 initially transformed [9-14C]phenanthrene to produce metabolites at the 9,10-, 1,2-, and 3,4- positions. Subsequently, sulfate conjugates of phase I metabolites were formed byA. niger, S. racemosum, andC. elegans. Minor glucuronide conjugates of 9-phenanthrol and phenanthrenetrans-9,10-dihydrodiol were formed byS. racemosum andA. niger, respectively. In addition,C. elegans produced the glucose conjugates 1-phenanthryl β-d-glucopyranoside and 2-hydroxy-1-phenanthryl β-d-glucopyranoside, a novel metabolite. [9-14C]Phenanthrene metabolites were not detected in organic extracts from biotransformation experiments with the yeasts,Candida lipolytica 37-1,Candida tropicalis ATCC 32113, andCandida maltosa R-42.

Journal ArticleDOI
TL;DR: All three Aspergillus polygalacturonases belong to the so‐called inverting glycanases, i.e. they utilize the single displacement mechanism of hydrolysis of the glycosidic linkage.

Journal ArticleDOI
TL;DR: Myristic acid analogs that are putative inhibitors of N‐myristoyl‐transferase were tested in vitro for activity against yeasts and filamentous fungi and exhibited potent activity against C. albicans, Cryptococcus neoformans and Aspergillus niger.
Abstract: Myristic acid analogs that are putative inhibitors of N-myristoyl-transferase were tested in vitro for activity against yeasts (Saccharomyces cerevisiae, Candida albicans, Cryptococcus neoformans) and filamentous fungi (Aspergillus niger). Several (+/-)-2-halotetradecanoic acids including (+/-)-2-bromotetradecanoic acid (14c) exhibited potent activity against C. albicans (MIC = 39 microM), C. neoformans (MIC = 20 microM), S. cerevisiae (MIC = 10 microM), and A. niger (MIC < 42 microM) in RPMI 1640 media. Improved synthetic methods have been developed for the synthesis of 12-fluorododecanoic acid (12a) and 12-chlorododecanoic acid (12c). Three novel fatty acids, 12-chloro-4-oxadodecanoic acid (8a), 12-phenoxydodecanoic acid (12i), and 11-(4-iodophenoxy)-undecanoic acid (13d) were also synthesized and tested.

Journal ArticleDOI
TL;DR: Of the fungal isolates tested, Aspergillus niger A-20 proved to be the most potent and produced highly active multienzyme systems after 5 days in shaken cultures, suggesting potential uses in the extraction of the major components of plant materials.

Journal ArticleDOI
TL;DR: No differences in the initiation or rate of citric acid accumulation were observed between the three strains, and the possible mechanisms by which ggsA controls glycolytic flux in A. niger in the presence of high sugar concentrations are discussed.
Abstract: Accumulation of citric acid by Aspergillus niger depends on a high flux through glycolysis. We have investigated the possibility of control of this flux by trehalose 6-phosphate, an inhibitor of hexokinase of Saccharomyces cerevisiae and other eukaryotes (Blasquez et al., FEBS Lett. (1993) 329, 51-54). Hexokinase of A. niger was shown in vitro to be only weakly inhibited by trehalose 6-phosphate (KI 1.5-2 mM). To investigate the in vivo relevance of this inhibition, we used isogenic strains of A. niger, carrying either a disruption or an amplification of the trehalose-6-phosphate synthase A (T6PSA)-encoding gene (ggsA) and exhibiting corresponding differences in T6PSA activity. These strains produced citric acid at comparable rates and with similar yields on 1 or 2.5% (w/v) sucrose. At 5-14% (w/v) sucrose, the ggsA disrupted strain initiated citric acid accumulation earlier, whereas the multicopy strain showed the reverse effect. When sucrose was replaced by lactose, which enabled only low rates of catabolism irrespective of its concentration (1-8%), no differences in the initiation or rate of citric acid accumulation were observed between the three strains. The possible mechanisms by which ggsA controls glycolytic flux in A. niger in the presence of high sugar concentrations are discussed.

Journal ArticleDOI
TL;DR: A recombinant wine yeast strain has been constructed expressing the gene coding for alpha-L-arabinofuranosidase B from Aspergillus niger under the control of the yeast actin gene promoter, allowing its purification and characterisation.
Abstract: A recombinant wine yeast strain has been constructed expressing the gene coding for a-L-arabinofuranosidase B from Aspergillus niger under the control of the yeast actin gene promoter. The protein is efficiently secreted by the recombinant yeast, allowing its purification and characterisation. The heterologous α-l-arabinofuranosidase B shows similar physico-chemical properties to the native enzyme. The wine produced in microvinification experiments using the recombinant yeast presents the same oenological characteristics as obtained with the untransformed strain. The a-L-arabinofuranosidase B protein is detected throughout the fermentation.

Journal ArticleDOI
TL;DR: Evidence is presented that ochratoxin A accounts for the activity of the methanol extract against larvae of the detritivorous beetle Carpophilus hemipterus (Nitidulidae) and corn ear worm Helicoverpa zea when incorporated into a pinto bean diet at levels less than those occurring naturally in the sclerotia.
Abstract: Ochratoxin A, a known mycotoxin with demonstrated toxicity to insects, has been isolated from the sclerotia of the fungus Aspergillus carbonarius NRRL 369. The sclerotia, harvested from a solid substrate fermentation of corn kernels at 28 degrees C, produced quantities of ochratoxin A exceeding 50 ppm/g dry weight of sclerotia. Evidence is presented that ochratoxin A accounts for the activity of the methanol extract against larvae of the detritivorous beetle Carpophilus hemipterus (Nitidulidae) (75% reduction in feeding rate) and corn ear worm Helicoverpa zea (50% mortality with 99% reduction in weight gain among surviving larvae) when incorporated into a pinto bean diet at levels less than those occurring naturally in the sclerotia.

Journal ArticleDOI
TL;DR: Results show that SBP does not contain the inducer for FAE-III, but does induce novel esterases, although there was an increase in esterase activity with added polygalacturonase.
Abstract: A ferulic acid esterase (FAE-III), which was induced by growth of Aspergillus niger CBS 120.49 on oat-spelts xylan, was capable of releasing ferulic acid from wheat bran but not from sugar-beet pulp (SBP) (Faulds CB, Williamson G (1994) Microbiology 140:779—787). Growth of this strain on SBP gave low levels of ferulic acid esterase activity (using methyl ferulate as substrate). A similar growth with a di⁄erent A. niger strain (CS 180) gave tenfold higher levels of esterase activity. Assaying culture filtrates obtained from A. niger CS 180 grown on SBP over a 3 to 10-day period against four simple phenolic methyl esters dem- onstrated that at least two esterases were produced, and, by comparison of substrate specificity, FAE-III was either absent or present only at low levels. Further- more, immunodetection of proteins did not detect the presence of FAE-III in culture supernatants of SBP- grown cultures, whereas it did in cultures grown on oat-spelts xylan. These results show that SBP does not contain the inducer for FAE-III, but does induce novel esterases. When A. niger CS 180 cultures were grown on di⁄erent carbon sources, esterase activity was in- duced on SBP, sugar-beet arabinan and oat-spelts xylan, but not on simple sugars or de-esterified sugar- beet pectin. Further, SBP-grown cultures co-inoculated with arabinanase, galactanase or xylanase did not ex- hibit increased levels of extracellular FAE activity or an earlier appearance of esterase activity, although there was an increase in esterase activity with added poly- galacturonase. These results show that novel esterases are induced by growth of A. niger on SBP.

Journal ArticleDOI
TL;DR: Glucoamylases produced by Aspergillus niger grown on wheat bran in solid cultures were purified and activity was strongly inhibited by Hg2+ while Mn2+ and Fe2+ were stimulatory.
Abstract: Glucoamylases produced by Aspergillus niger grown on wheat brain in solid cultures were purified. Four different forms, GA I, GA I', GA II and GA III, were found having apparent molecular weights of 112,000, 104,000, and 74,000 and 61,000 Da respectively. The enzymes are glycoproteins with a carbohydrate content of 16%, and optimal activity at 60 degrees C and pH 4.4. Activity was strongly inhibited by Hg2+ while Mn2+ and Fe2+ were stimulatory. The Km values for the degradation of starch and maltose were 3.5 and 7.8 mg ml-1, respectively.

Journal ArticleDOI
TL;DR: Both endoglucanase and β-glucosidase activities were found in cell wall, cell-free extracts and extramycelial fractions of Trichoderma reesei cultures grown on amorphous cellulose.