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effect of initial ph on aflatoxin production.the effect of initial ph on aflatoxin production by aspergillus parasiticus nrrl 2999 was examined in a semisynthetic medium. maximal growth, aflatoxin production, and aflatoxin production per unit of growth occurred at initial ph levels of 5.0, 6.0, and 7.0 respectively. initial ph levels less than ph 6.0 favored production of the b toxins, whereas levels greater than ph 6.0 favored production of the g toxins.19752104
aflatoxin is degraded by mycelia from toxigenic and nontoxigenic strains of aspergilli grown on different substrates.the ability of 9-day-old mycelia of aspergillus parasiticus nrrl 2999 to degrade aflatoxin varied depending on the substrate used to grow the mold. substrates which allowed substantial mycelial growth yielded mycelia which actively degraded aflatoxin. substrates which allowed minimal growth of mycelia yielded mycelia with little ability to degrade aflatoxin. biodegradation of aflatoxin was also strain-dependent. a. parasiticus nrrl 2999 and nrrl 3000 actively degraded aflatoxin, a. flavus nrrl 3 ...197899656
[effect of sterigmatocystin on the toxinogenesis of the aspergillus flavus group].the aflatoxinogenesis of aspergillus parasiticus is significantly enhanced by the presence, in the medium, of sterigmatocystin at a high level (35--50 microgram/ml); low concentrations, in the order of 175 microgram/ml, have no effect on the production of aflatoxins. during the period where the aflatoxinogenesis of the culture is high, no variation of the sterigmatocystin level is noted, experiments with 14c-sterigmatocystin indicate that the mold does not utilize the metabolite itself as a prec ...1979119164
production of aflatoxin b1 and g1 by aspergillus parasiticus on silica gels.silica gels were prepared by acidifying alkaline silicate solutions with phosphoric or tartaric acid. various combinations of glucose, sucrose, yeast extract, and salts were included in the gels an nutrients. maximum production of aflatoxins b1 and g1 occurred when silica gel (0.4 to 0.5 cm deep in a petri dish) containing 20% sucrose and 2% yeast extract, and gelled with tartaric acid, was inoculated with approximately 120 to 12000 spores of aspergillus parasiticus per plate; and plates were in ...1977193316
effects of trace metals on the production of aflatoxins by aspergillus parasiticus.certain metals added as salts to a defined basal culture medium influenced the level of aflatoxin production by aspergillus parasiticus in the low micrograms-per-milliliter range of the added metal. in many cases no change or a relatively small change in mat weight and final ph of the medium accompanied this effect. with zinc at added levels of 0 to 10 mug/ml in the medium, aflatoxin increased 30-to 1,000-fold with increasing of zinc, whereas mat weight increased less than threefold. at 25 mug o ...1975238471
malonate as a precursor in the biosynthesis of aflatoxins.incorporation of [i-14c]acetate and [2-14c]malonate into aflatoxins by resting mycelia of aspergillus parasiticus resuspended in different buffers was studied. a decrease in ph from 5-8 to 2-8, as well as addition of edta, markedly stimulated the incorporation of malonate but the effect on acetate incorporation was less pronounced. mycelia took up comparatively more acetate than malonate, but more malonate (4-3%) entering mycelia was incorporated into aflatoxins than was acetate (1-6%). furtherm ...1975239093
aflatoxin production by aspergillus parasiticus in a competitive environment.aspergillus parasiticus nrrl 2999 was grown in the presence of rhizopus nigricans, saccharomyces cerevisiae, acetobacter aceti, or brevibacterium linens and aflatoxin concentration was determined after 3,5,7, and 10 days of incubation at 28c. r. nigricans and s. cerevisiae inhibited growth and aflatoxin production by a. parasiticus. b. linens caused slight inhibition and a. aceti stimulated growth and aflatoxin production by a. parasiticus.1977339094
inhibitory effects of condiments and herbal drugs on the growth and toxin production of toxigenic fungi.the effects of thirteen kinds of powdered herbal drugs and seven kinds of commercial dry condiments on the growth and toxin production of aspergillus parasiticus, a. flavus, a. ochraceus, and a. versicolor were observed by introducing these substances into culture media for mycotoxin production. of the twenty samples tested, cinnamon bark completely inhibited the fungal growth, while the others only inhibited the toxin production. the inhibitors were easily extracted from the samples with solven ...1979440403
aflatoxins and anthraquinones from diploids of aspergillus parasiticus.three spore colour, two mycelial colour and 12 auxotrophic mutants were isolated from an aflatoxigenic strain of aspergillus parasiticus. these mutants and heterozygous diploids formed by pairwise combinations of auxotrophs were assayed for aflatoxin production; norsolorinic acid and versicolorin a production were also assayed in the diploids. in general, introduction of an auxotrophic marker lowered aflatoxin production in haploids. the green-spored, prototrophic diploids resembled haploid wild ...1979501330
[effect of zinc ions and aeration on glucose catabolism in aspergillus parasiticus]. 1979517170
factors affecting aflatoxin production by aspergillus parasiticus in a chemically defined medium.the optimum levels of sucrose, (nh4)2so4, mgso4, kh2po4 and znso4 for aflatoxin production in a chemically defined medium have been established. the last two were found to be essential for fungal growth and aflatoxin production. the effect of various carbon sources on aflatoxin production was tested using the defined medium. asparagine was found to be essential for aflatoxin production. very little aflatoxin was produced in the absence of asparagine with any of the other inorganic nitrogen sourc ...1979541661
biosynthesis of aflatoxins.the role of zinc on the primary metabolism of aspergillus parasiticus in relation to aflatoxin biosynthesis was studied. zinc deficiency impaired growth and metabolism of nucleic acid and protein while stimulating that of lipid. the activities of enzymes of glycolytic cycle were affected indicating that these are zinc dependent enzymes. impaired glycolytic cycle tends to reduce the level of primary metabolites like pyruvate, citrate and oxaloacetate which trigger aflatoxin formation. during stat ...1977613925
isolation, purification, and antibiotic activity of o-methoxycinnamaldehyde from cinnamon.o-methoxycinnamaldehyde has been isolated and purified from powdered cinnamon. the compound inhibits the growth and toxin production of mycotoxin-producing fungi. the substance completely inhibited the growth of aspergillus parasiticus and a. flavus at 100 microgram/ml and a. ochraceus and a. versicolor at 200 microgram/ml. it inhibited the production of aflatoxin b1 by over 90% at 6.25 microgram/ml, ochratoxin a at 25 microgram/ml, and sterigmatocystin at 50 microgram/ml. the substance also dis ...1978708030
the parasexual cycle in aspergillus parasiticus. 1978723913
[effect of cultivation conditions on aflatoxin biosynthesis by aspergillus parasiticus]. 1978747121
production of aflatoxins b1 and g1 by aspergillus flavus and aspergillus parasiticus isolated from market pecans.one hundred and forty-eight isolates of aspergillus flavus and a. parasiticus were isolated from 5,608 pecans obtained from chicago and georgia markets. the percentage of internal contamination by these species was 7.3% in the chicago market pecans and 1.7% in those from markets in georgia. of the 148 isolates, 93% of the a. parasiticus, but only 54% of the a. flavus, were capable of producing aflatoxin. overall, 57% of the isolates were potentially aflatoxigenic. a. parasiticus isolates general ...1975811163
effect of temperature cycling on the production of aflatoxin by asperfillus parasiticus.aspergillus parasiticus (nrrl 2999) was grown under cycling temperature conditions on rice and nutmeat substrates. under conditions of diurnal and nocturnal time-temperature sequencing, total heat input is an important factor of toxin production. when expressed in degree hours per day, thermal input becomes more definitive and provides a finite number, which can be related to observable changes in the culture such as sporulation and toxin biosynthesis. three well-defined levels of response were ...1976825039
aflatoxin biosynthetic pathway: elucidation by using blocked mutants of aspergillus parasiticus. 1977836036
production of aflatoxin by aspergillus parasiticus nrrl-2999 during growth in the presence of curing salts.aspergillus parasiticus nrrl-2999 was inoculated into meat mixtures with curing salts and into yeast extractsucrose (yes) and sucrose-ammonium salts (sas) broth with and without curing salts to determine if the presence of curing salts significantly affected growth and aflatoxin production by the mold. the effect of individual curing salts or curing salt mixtures on growth and toxin elaboration by the aspergillus was substrate dependent. when yes broth contained 100 ppm of nano2, 2% nacl, or 1 o ...1977917104
effect of acetone on production of aflatoxins and versicolorin pigments by resting cell cultures of aspergillus parasiticus.resting cell cultures of aspergillus parasiticus were grown in medium containing four different concentrations of glucose, with and without acetone. in addition, the effect of different equimolar concentrations of acetone, acetic acid, ethanol, and sodium acetate was compared at two glucose levels. aflatoxin and versicolorin pigment production increased in resting cell medium containing increasing concentrations of glucose. in the presence of glucose high concentrations of acetone (1.0 and 0.25 ...1976934261
[effect of aflatoxin b1, of some of its metabolites and of culture extracts from "aspergillus parasiticus" on virulent bacteriophages (author's transl)].aflatoxin b1 has different effects on bacteriophages: it inhibits some virulent strains and induces lysogenic bacteria. in this experiments we have used several classes of phages of enterobacteria, streptococci, staphylococci and bacillus. we have tested different substances: cristallized aflatoxin b1, metabolites of the same mycotoxin and culture extracts from a toxinogenic strain of aspergillus parasiticus. the inhibitory effects observed are different for each strain, and for a given phage th ...19761035487
biosynthesis of averufin from acetate by aspergillus parasiticus. 19751150990
production of aflatoxin on soybeans.probable factors influencing resistance to aflatoxin synthesis in soybeans have been investigated by using cultures of aspergillus parasiticus nrrl 3240. soybeans contain a small amount of zinc (0.01 mug/g) bound to phytic acid. autoclaving soybeans at 15 pounds (6803.88 g) for 15 min increases the aflatoxin production, probably by making zinc available. addition of zinc to both autoclaved and nonautoclaved soybeans promotes aflatoxin production. however, addition of varying levels of phytic aci ...19751171654
excretion of carbon-14-labeled aflatoxin b1 via bile, urine, and intestinal contents of the chicken.carbon-14-labeled aflatoxin b1 was prepared by growing aspergillus parasiticus in medium containing sucrose-14-c as the sole carbon source. the 14-c-labeled aflatoxin b1 was extracted with chloroform and purified by thin-layer chromatography (tlc) followed by precipitation from solution and washing. the 14-c-labeled aflatoxin b1 was intravenously given to anesthetized dwarf white leghorn or rhode island red hens with cannulated ureters and bile ducts. the 14-c had a calculated plasma half-life o ...19751147354
inhibition of aflatoxin formation by 2-mercaptoethanol.2-mercaptoethanol inhibits growth of aspergillus parasiticus nrrl 3240 and aflatoxin formation by the fungus. when added to the resuspended medium, 2-mercaptoethanol inhibited [1-14c]acetate incorporation into both aflatoxins and neutral lipids, thereby showing that it acts at an early stage of aflatoxin biosynthesis. the inhibition is probably due to its chelating action on zinc, which is essential for aflatoxin production. it is proposed that any chelating agent that selectively binds to zinc ...1976984814
synthesis of aflatoxins by the non-growing mycelia of aspergillus parasiticus and the effect of inhibitors. 19751206377
the effect of inorganic salts and some biologically important compounds on the incorporation of 1-14c acetate into aflatoxins by resting mycelia of aspergillus parasiticus.zn++, mg++, and mn++ ions at certain concentrations, stimulated the incorporation of [1-14c] acetate-into aflatoxins by resting mycelia of aspergillus parasiticus suspended in tris-hcl buffer of ph 7.2. ba++ gave consistant stimulation over a wide range of concentrations. ethanol markedly inhibited the incorporation. of the tricarboxylic acid cycle intermediates, citric acid gave the maximum stimulation.19751224789
aflatoxin can be degraded by the mycelium of aspergillus parasiticus.aflatoxins b1, b2, g1, and g2 were degraded by the 8- and 16-day old but not by the 4-day old mycelium of a toxigenic strain of aspergillus parasiticus. the 16-day old mycelium degraded the toxin more rapidly than did the 8-day old mycelium. degradation of toxin by the mycelium was similar at ph 2.5 and 6.0.19751229716
the effect of zinc and phytic acid on the incorporation of 1-14c-acetate into aflatoxin by resting mycelia of aspergillus parasiticus.the effect of zinc and phytic acid on [1-14c]-acetate incorporation into aflatoxins by resting mycelium was studied. when different levels of znso4 were used to study its effect on the incorporation of [1-14c]-acetate into aflatoxins, it was found that the specific radioactivity incorporation into aflatoxins was maximum at the level of 10 mm-znso4. at this concentration the change in the specific radioactivities of aflatoxins b1 + b2 and aflatoxins g1 + g2 were +74.61% and +29.66%, respectively. ...19751229717
effects of fungus (aspergillus parasiticus) toxins on the chromosomes of human lymphocytes in vitro. 1977906035
effect of zinc on tricarboxylic acid cycle intermediates and enzymes in relation to aflatoxin biosynthesis.the stimulatory action of zinc on aflatoxin production by aspergillus parasiticus nrrl3240 has been investigated by studying the levels of tricarboxylic acid (tca) cycle intermediates and related enzymes in the fungal mycelium. during the stationary phase of growth, the levels of alpha-keto acids declined in zinc-sufficient cultures compared with those in zinc-dificient cultures. tca cycle enzymes did not show any significant changes due to zinc availability. in zinc-deficient cultures, enzymes ...1977864436
aflatoxin is degraded by heated and unheated mycelia, filtrates of homogenized mycelia and filtrates of broth cultures of aspergillus parasiticus.steaming one-half of a lot of 9-day-old mycelia of aspergillus parasiticus nrrl 2999 for 6 min resulted in little or no subsequent degradation of aflatoxin b1 or g1 by these mycelia. the other half of these mycelia was not heat-treated and degraded aflatoxins b1 and g1. filtrates of the growth substrate which remained after the mycelium was removed from 8- to 15-day old cultures of a. parasiticus nrrl 2999 did not degrade substantial amounts of aflatoxin b1 or g1, whereas mycelia originally prod ...1978714150
inhibition of aflatoxin biosynthesis by tolnaftate.tolnaftate [2-napthyl-n-methyl-n-(m-tolyl)thionocarbamate], an antifungal drug, is widely used to control superficial fungal infections in humans and other animals. in this study the effect of tolnaftate on aflatoxin biosynthesis by aspergillus parasiticus nrrl 3240 was investigated. tolnaftate changed the morphology of a. parasiticus to yeastlike forms and inhibited aflatoxin formation. the formation of aflatoxin g was blocked considerably, indicating a metabolic block in the conversion of afla ...1978697362
aflatoxin at several initial concentrations is degraded by different amounts of mycelium of aspergillus parasiticus.increasing amounts of a blendure of 9-day-old mycelia of aspergillus parasiticus nrrl 2999 added to aflatoxin-salts reaction mixtures resulted in increased rates at which aflatoxin b1 and g1 were degraded. similarly, increasing the amount(s) of aflatoxin b1 and/or g1 in the aflatoxin-salts reaction mixture resulted in increased rates of degradation of aflatoxins b1 and g1 by mycelia. this mycelial blendure degraded aflatoxin g1 approximately 1.6 times more rapidly than aflatoxin b1 when comparab ...1978695964
degradation of aflatoxin by lactoperoxidase.three concentrations of lactoperoxidase, 5, 50, and 500 units/ml of reaction mixture, degraded aflatoxin in the presence of 225 micrometer nacl and 50 micrometer h2o2 at 28 degrees c. increasing the amount of lactoperoxidase from 50 to 500 units/ml of reaction mixture resulted in increasing the rate of degradation of aflatoxin b1 from 3.6 to 5.1%/24 h. when comparable amounts of lactoperoxidase were present, aflatoxin g1 was degraded approximately 1.5 times faster than was aflatoxin b1. at a giv ...1978685475
[comparison of methods for the quantitative detection of moulds in foods. iii. comparison of different culture media for the mould plate count (author's transl)].the mould plate count and taxonomical grouping of the mould flora of 9 moulded non-fluid foods were compared on totally 12 different media, which are commonly used for the detection of moulds.--in contrary to the bacteriological practice, moulds should only be counted on plates with 20-50 colonies, as on plates covered densely with a mixed mould flora, simple colonies are often no more detectable. mould plate counts of all tested products were in the same range on all media with a sugar content ...1978568864
[influence of cooling temperatures on aflatoxin formation in milk products (author's transl)].in the literature several contradictionary results have been published on the aflatoxin formation at temperatures below 10 degrees c. therefore experiments with pastes made from milk and cheese powder artificially contaminated with aspergillus parasiticus, were performed at temperatures of 1 degree c, 5 degrees c, and 10 degrees c for 28 days at a relative humidity of 90--95%. even at 1 degree c, the aflatoxins b1, b2, g1, g2, and m1 could be determined quantitatively. the lactose content did no ...1977562043
aflatoxin production via cross-feeding of pathway intermediates during cofermentation of aflatoxin pathway-blocked aspergillus parasiticus mutants.cofermentation of aspergillus parasiticus strains (srrc 163 and srrc 2043) blocked at different steps in the aflatoxin b1 (afb1) biosynthetic pathway in a synthetic liquid medium or on seeds (cottonseed, corn kernels, and peanuts) resulted in production of afb1. strain srrc 2043 accumulated o-methylsterigmatocystin (omst), a late precursor in afb1 biosynthesis, whereas srrc 163 accumulated averantin, an early precursor in the pathway. strain srrc 2043 secreted large amounts of omst in culture re ...19911746952
a metabolic grid among versiconal hemiacetal acetate, versiconol acetate, versiconol and versiconal during aflatoxin biosynthesis.dichlorvos treatment of aflatoxigenic aspergillus parasiticus sys-4 (nrrl 2999) or a verscolorin a-accumulating mutant, niah-9, resulted in accumulation of versiconol acetate (voac) and versiconal hemiacetal acetate (vha), whereas the production of aflatoxins, versicolorin a (va), and versiconol (voh) decreased. in feeding experiments using another non-aflatoxigenic mutant, niah-26, aflatoxins were newly produced from each of vha, voac, voh, versicolorin b (vb) and versicolorin c (vc). in these ...19911770361
influence of trace elements and nitrogen sources on versicolorin production by a mutant strain of aspergillus parasiticus.a mutant strain of aspergillus parasiticus blocked in aflatoxin biosynthesis accumulates versicolorin a and versicolorin c. the effect of trace elements on the growth and versicolorin production by this strain was studied in a defined medium. the omission of manganese was slightly stimulatory to versicolorin production; when zinc was omitted from the medium, no detectable versicolorins were produced. experiments on nitrogen sources in a high-sucrose medium indicated that fourfold to fivefold inc ...1979530298
production of aflatoxin in cocoa beans.aflatoxin was produced in both non-autoclaved and autoclaved ivory coast cocoa beans inoculated with aspergillus parasiticus nrrl 2999 under optimum laboratory growth conditions. total aflatoxin levels ranged from 213 to 5597 ng/g substrate. aflatoxin was quantitated by using high pressure liquid chromatography (hplc). raw, non-autoclaved cocoa beans, also inoculated with aspergilli, produced 6359 ng aflatoxin/g substrate. variation in aflatoxin production between bean varieties was observed. to ...1979528451
effect of graded doses of gamma-irradiation on aflatoxin production by aspergillus parasiticus in wheat. 1979520984
enzymatic conversion of norsolorinic acid to averufin in aflatoxin biosynthesis.5'-hydroxyaverantin (havn) was isolated from a mold, emericella heterothallica ifo 30842. aspergillus parasiticus niah-26, a uv-irradiated mutant of a. parasiticus sys-4, produced neither aflatoxins nor precursors in yeast extract-sucrose (yes) medium. when the postmicrosome (cytosol) fraction of niah-26, which had been prepared from the culture in yes medium, was incubated with norsolorinic acid (na) in the presence of nadh or nadph, averantin (avn) was produced. the reverse reaction from avn t ...19911854196
effect of peanut tannins on percent seed colonization and in vitro growth by aspergillus parasiticus.the relationship between tannin content of mature, intact, cured peanut seed and percent seed colonization by aspergillus parasiticus was examined. tannin content in 9 cultivars, 7 of which were grown in both tifton, georgia and puerto rico, was significantly correlated with percent seed colonization. for data expressed as mg tannin/g intact seed and mg tannin/g seed coat, correlation coefficients with percent colonization were 0.74 and 0.76, respectively. seed coat tannin, methanol-extracted, w ...1979440404
the effect of various antifungal agents on aflatoxin production and growth characteristics of aspergillus parasiticus and aspergillus flavus in liquid medium.various antifungal agents were added to a medium of 2% yeast extract-4% sucrose. spores of a toxigenic strain of aspergillus parasiticus were inoculated into the medium and incubated at 26 degrees c. for 10 days. growth of the mold and aflatoxin formation were monitored every 48 hours during the experiment. of the antifungal agents evaluated, propionic acid and crystal violet were the most effective compounds in retarding mold growth. propionic acid was fungicidal at concentrations greater than ...1977415299
aflatoxins in food: occurrence, biosynthesis, effects on organisms, detection, and methods of control.aflatoxins are secondary metabolites produced by species of aspergilli, specifically aspergillus flavus and aspergillus parasiticus. these molds are ubiquitous in nature and grow on a variety of substrates, thereby producing aflatoxins. aflatoxins are of great concern due to their biochemical and biological effects on living organisms. in this article, the occurrence of aflatoxins, their biosynthesis, factors influencing their production, their effects on living organisms, and methods of detecti ...19911910523
aflatoxin localization by the enzyme-linked immunocytochemical technique.visualization of aflatoxin deposits within aspergillus parasiticus atcc 15517 hyphae was made possible by using an enzyme-linked immunocytochemical technique.1977329764
regulation of aflatoxin biosynthesis. 1 comparative study of mycelial composition and glycolysis in aflatoxigen and nonaflatoxigenic strains.a comparative biochemical study of an aflatoxigenic strain aspergillus parasiticus nrrl 3240 and a nonaflatoxigenic strain a. flavus nrrl 3237 was carried out in order to have a better idea of regulation of aflatoxin biosynthesis. the results obtained revealed continuous primary metabolic activity (protein synthesis) in the nonaflatoxigenic strain while the aflatoxigenic stain showed inhibition of protein and nucleic acid synthesis. the aflatoxigenic strain showed higher levels of oxygen uptake, ...1977204853
growth of, and aflatoxin production by aspergillus parasiticus when in the presence of either lactococcus lactis or lactic acid and at different initial ph values.aspergillus parasiticus was grown in a modified lab-lemco tryptone broth both as a single culture and in association with lactococcus lactis. total aflatoxin (b1 + g1) production was higher in the mixed cultures. this stimulation persisted when different batches of media, inoculation procedures and makes of ingredients were used. aflatoxin yields increased in media with an initial ph of 4.2 compared with a ph close to neutrality. hydrochloric and/or lactic acid had little effect. the substitutio ...19902127265
regulation of aflatoxin biosynthesis. 2 comparative study of tricarboxylic acid cycle in aflatoxigenic and non-aflatoxigenic strains of aspergillus flavus.the presence of a functional tca cycle and its intermediates has been shown in aspergillus parasiticus and aspergillus flavus. the role of the tca cycle in aflatoxin biosynthesis has been studied. in a. parasiticus the tca cycle was activated on the second day of growth (exponential growth phase) resulting in the onset of aflatoxin biosynthesis. pyruvate accumulation to toxic levels in a. parasiticus is suggested to shift the growth phase from exponential to stationary with the onset of aflatoxi ...197799644
versicolorin a hemiacetal, hydroxydihydrosterigmatocystin, and aflatoxin g2 alpha reductase activity in extracts from aspergillus parasiticus.versicolorin a hemiacetal was converted to versicolorin c in cell-free systems from aspergillus parasiticus. the rate of reaction catalyzed by the 35-70% ammonium sulfate fraction was 0.43 nmol min-1 mg-1 with nadph as cosubstrate and 0.17 nmol min-1 mg-1 with nadh at 25 degrees c at ph 7.4. the product from incubation of 17-hydroxy-16,17-dihydrosterigmatocystin with the 35-70% ammonium sulfate fraction and nadph was a polar compound which was converted to dihydrosterigmatocystin by 0.4 m hcl. t ...19902233978
a pathway of polygalactosamine formation in aspergillus parasiticus: enzymatic deacetylation of n-acetylated polygalactosamine.1. an enzyme which hydrolyzes the acetamido groups of n-acetylgalactosamine residues in n-acetylated polygalactosamine was found in the supernatant fraction of aspergillus parasiticus ahu 7165, a polygalactosamine-producing strain. 2. n-acetylated polygalactosamine was used as a substrate in the purification and characterization of this enzyme. a 140-fold purification was obtained by means of ammonium sulfate fractionation followed by chromatography on carboxymethylcellulose and deae-cellulose. ...197942541
enzymatic conversion of sterigmatocystin into aflatoxin b1 by cell-free extracts of aspergillus parasiticus.a cell-free extract, prepared from aspergillus parasiticus atcc 15517 grown in synthetic medium, was active in converting 14csterigmatocystin into aflatoxin b1 in the presence of reduced nicotinamide adenine dinucleotide phosphate. the activity was demonstrated by the time course of conversion and the linear dependence of the yield of product on enzyme concentrations. optimum activity was obtained at ph 7.5 to 7.8 at 27 c. the results confirm sterigmatocystin as a biogenetic precursor of aflatox ...19765954
effect of zinc on adenine nucleotide pools in relation to aflatoxin biosynthesis in aspergillus parasiticus.the adenylic acid systems of aspergillus parasiticus were studied in zinc-replete and zinc-deficient media. the adenosine 5'-triphosphate levels of the fungus were high during exponential phase and low during stationary phase in zinc-replete cultures. on the other hand, the levels of adenosine 5'-diphosphate and adenosine 5'-monophosphate were low during exponential phase of growth and high during stationary phase. the adenosine 5'-triphosphate levels during exponential phase may indicate higher ...19761008554
14c-labeled aflatoxin b1 prepared with yeastlike cultures of aspergillus parasiticus.a simple method was developed to produce 14c-labeled aflatoxin b1 by using the yeastlike phase of aspergillus parasiticus nrrl 2999. yeastlike cultures resulted from absence of manganese in a synthetic medium. sodium acetate-1-14c had a 0.22% average incorporation; sodium acetate-1,2-14c, 0.70%. the average yield of labeled b1 was 10 mg/500 ml medium with an average specific activity of either 63.3 mci/mole (c-1 label) or 194.3 mci/mole (c-1, 2 label).19761002952
inhibitory effects of anethole and eugenol on the growth and toxin production of aspergillus parasiticus.the antifungal and antiaflatoxigenic activity of anethole and eugenol which are active components of commonly used spices was studied against two strains of aspergillus parasiticus. anethole, up to concentration of 400 micrograms/ml where complete inhibition was observed, delayed growth and reduced mycelial weight but it showed a stimulative effect on the toxin production of both strains. at a concentration of 300 micrograms/ml, eugenol inhibited the growth of both strains; levels of eugenol bel ...19902397152
intracellular hydrolases of aspergillus parasiticus and aspergillus flavus.when the distribution profile of hydrolases in mycelial homogenates and culture filtrates of a. parasiticus and a. flavus was examined, six hydrolytic enzymes viz. n-acetyl-beta-glucosaminidase, aryl sulfatase, alkaline proteinase, cathepsin b, cathepsin d and aminopeptidase were detected in homogenate. the culture filtrates were devoid of any activity of these enzymes. the enzyme levels varied with the stage of incubation. the most abundant fungal exopeptidase showing preference for basic amino ...19892494993
direct visual detection of aflatoxin synthesis by minicolonies of aspergillus species.single-spore colonies of aspergillus flavus and aspergillus parasiticus, grown for 4 to 5 days at 25 degrees c on a coconut extract agar containing sodium desoxycholate as a growth inhibitor, produced aflatoxin, readily detectable as blue fluorescent zones under long-wave (365 nm) uv light. over 100 colonies per standard petri dish were scored for aflatoxin production by this procedure. progeny from some strains remained consistently stable for toxin production after repeated subculture, whereas ...19892504116
biosynthesis of aflatoxin b1. conversion of versicolorin a to aflatoxin b1 by aspergillus parasiticus. 19761002895
inhibition of growth and aflatoxin production of aspergillus parasiticus by citrus oils.aspergillus parasiticus was inoculated into grapefruit juice and a glucose-yeast extract medium; both contained 500-7000 ppm of citrus oils that were incorporated into the media by sonication. orange and lemon oil were more inhibitory to mold growth and aflatoxin production than was dlimonene, the main constituent of the two peel oils. after 7 days at 28 degrees c, 2000 ppm of lemon and 3000 ppm of orange oil in grapefruit juice afforded maximum suppression of mold growth and toxin formation. wh ...1976973437
synthesis of versicolorin a by a mutant strain of aspergillus parasiticus deficient in aflatoxin production. 19751194578
mycotoxins and reproduction in domestic livestock.molds are parasitic plants that are ubiquitous in livestock feedstuffs. even though molds themselves reduce the quality of grains, their synthesis of chemical substances termed mycotoxins causes the greatest monetary loss to the animal industry. five major mycotoxins that impair growth and reproductive efficiency in north america are aflatoxins, zearalenone, deoxynivalenol, ochratoxin, and ergot. aflatoxins are produced by aspergillus flavus and aspergillus parasiticus. consumption of grains con ...19921388147
aflatoxins in sunflower seeds: influence of alternaria alternata on aflatoxin production by aspergillus parasiticus.the aim of the present work was to determine the influence of alternaria alternata upon aflatoxin production by aspergillus parasiticus. a mixture of spores of both strains was inoculated in sunflower seeds at 0.90 aw and incubated for 42 days at 28 degrees c +/- 1. the cultures were observed and analyzed every 7 days to determine the infection level of the seeds and the production of aflatoxins. results showed that when the seeds were inoculated only with aspergillus parasiticus, 100% were infe ...19892615799
production of aflatoxin and its partition between the medium and the mycelium of aspergillus parasiticus during incubation under various conditions.spores of an aflatoxigenic strain of aspergillus parasiticus were inoculated into a glucose-salts medium which was incubated with and without shaking at 28 degrees c for 15 days. without shaking, maximal production of total aflatoxin and aflatoxins b1, g1, and g2 occurred at 5 days, whereas the maximal amount of b2 appeared after 7 days. initially approximately 5% of the total toxins appeared in the mycelium but this increased to more than 60% after 5 days. shaking of cultures during incubation ...19751189619
effect of some inhibitors on aflatoxin-production in a synthetic medium and on the incorporation of acetate-1- 14c into aflatoxins by resting mycelia of aspergillus parasiticus.the effect of a number of metabolic inhibitors on the incorporation of acetate-1-14c into aflatoxins was investigated, using resting mycelia of aspergillus parasiticus suspended in phosphate buffer. malonate, iodoacetate, sodium arsenite, 2:4 dinitrophenol, sodium fluoride and p-aminosalicylate stimulated the incorporation at low concentrations and inhibited the same at high concentrations. p-nitrobenzoic acid was inhibitory at all the concentrations tried. fluoride, arsenite, arsenate and iodoa ...19761260151
effect of some food preservatives on aflatoxin production.the effect of some food preservatives, such as sorbic (sa) and propionic (pa) acids, on aflatoxin production in synthetic media or in moistened (20%) wheat seeds, was investigated. the preservatives tested, added to synthetic media at sublethal concentrations both at the inoculum and after 5 days of incubation, stimulated aflatoxin production by aspergillus parasiticus. sorbic and propionic acids are metabolized by the fungus in vivo and in vitro. lower concentrations of pa and sa (0.05 to 0.1% ...19921298645
aflatoxin production by entomopathogenic isolates of aspergillus parasiticus and aspergillus flavus.fourteen isolates of aspergillus parasiticus and 2 isolates of aspergillus flavus isolated from the mealybug saccharicoccus sacchari were analyzed for production of aflatoxins b1, b2, g1, and g2 in liquid culture over a 20-day period. twelve aspergillus isolates including 11 a. parasiticus and 1 a. flavus produced aflatoxins which were extracted from both the mycelium and culture filtrate. aflatoxin production was detected at day 3 and was detected continually for up to day 20. aflatoxin b1 prod ...19902112577
two distinct o-methyltransferases in aflatoxin biosynthesis.the substances belonging to the sterigmatocystin group bear a close structural relationship to aflatoxins. when demethylsterigmatocystin (dmst) was fed to aspergillus parasiticus niah-26, which endogenously produces neither aflatoxins nor precursors in yes medium, aflatoxins b1 and g1 were produced. when dihydrodemethylsterigmatocystin (dhdmst) was fed to this mutant, aflatoxins b2 and g2 were produced. results of the cell-free experiment with s-adenosyl-[methyl-3h]methionine showed that first t ...19892802602
enzymological evidence for separate pathways for aflatoxin b1 and b2 biosynthesis.aflatoxins b1 (afb1) and b2 (afb2) are biologically active secondary metabolites of aspergillus flavus and aspergillus parasiticus. these toxins are synthesized by the fungi from pathway precursors: sterigmatocystin (st)----o-methylsterigmatocystin (omst)----afb1; dihydrosterigmatocystin (dhst)----dihydro-o-methylsterigmatocystin (dhomst)----afb2. the late stages of afb1 synthesis are carried out by two enzyme activities, a methyltransferase (mt) (st----omst), and an oxidoreductase (or) (omst--- ...19911902378
nitrate induces enzymes of the mannitol cycle and suppresses versicolorin synthesis in aspergillus parasiticus.addition of sodium nitrate to growing cultures of aspergillus parasiticus (atcc 36537) induces the synthesis of enzymes involved in nitrate assimilation (no3- reductase), of enzymes in the pentose pathway (glucose-6-phosphate dehydrogenase), and of enzymes in the mannitol cycle (mannitol- and mannitol-1-phosphate dehydrogenases). addition of no3- also causes a dose-dependent suppression of synthesis of the polyketide secondary metabolite, versicolorin a. we suggest that in the presence of no3- p ...19892615792
nitrogen metabolism in aspergillus parasiticus nrrl 3240 and a. flavus nrrl 3537 in relation to aflatoxin production.the relationship between nitrogen assimilation, metabolism and aflatoxin formation has been investigated in a toxigenic and a non-toxigenic strain of aspergillus parasiticus. ammonia from the medium is mainly assimilated via nadp-requiring glutamate dehydrogenase. during growth nad-requiring glutamate dehydrogenase followed an inverse pattern of activity with respect to nadp glutamate dehydrogenase. alpha-ketoglutarate, the product of nad glutamate dehydrogenase, stimulated acetate incorporation ...19862872196
mycotoxin-producing fungi from house associated with leukemia.fungi were isolated from a house associated with four leukemic patients from three families because of the possibility that mycotoxin-producing strains might be present. extracts of several of the isolated fungal species produced toxic effects in one or more species of animals. aflatoxin-producing aspergillus parasiticus was isolated from non-leukemia-associated houses with the exception of trichoderma, verticillium, and monotospora. we believe that certain mycotoxins may be related to pathogene ...19751239242
a versiconal hemiacetal acetate converting enzyme in aflatoxin biosynthesis.conversion of the aflatoxin biosynthetic intermediate versiconal hemiacetal acetate (vha) in a cell free extract of aspergillus parasiticus atcc 15517 is investigated. the enzymatic reaction is monitored by a method using high performance liquid chromatography (hplc). the major product of the enzymatic reaction is a water soluble compound not chloroform-extractable at ph 7.5. the product becomes chloroform extractable upon acidification of the reaction medium and is separated and quantitated by ...19892615791
purification and properties of versiconal cyclase from aspergillus parasiticus.versiconal cyclase catalyzes the dehydration of versiconal to versicolorin b or versicolorin c [versicolorin b(c)]. the enzyme was purified from mycelia of aspergillus parasiticus by deae-cellulose, hydroxylapatite, and mono q column chromatography. the protein contains two identical subunits of molecular weight 72,000 per molecule of native protein. the pi of the enzyme is 3.95. the ph activity curve had a broad maximum with a peak at 5.5. the km and vmax for versiconal at 30 degrees c and ph 6 ...19921731640
averufanin is an aflatoxin b1 precursor between averantin and averufin in the biosynthetic pathway.wild-type aspergillus parasiticus produces, in addition to the colorless aflatoxins, a number of pigmented secondary metabolites. examination of these pigments demonstrated that a major component was an anthraquinone, averufanin. radiolabeling studies with [14c]averufanin showed that 23% of the label was incorporated into aflatoxin b1 by the wild type and that 31% of the label was incorporated into o-methylsterigmatocystin by a non-aflatoxin-producing isolate. in similar studies with blocked mut ...19873103529
identification of o-methylsterigmatocystin as an aflatoxin b1 and g1 precursor in aspergillus parasiticus.an isolate of aspergillus parasiticus cp461 (srrc 2043) produced no detectable aflatoxins, but accumulated o-methylsterigmatocystin (omst). when sterigmatocystin (st) was fed to this isolate in a low-sugar medium, there was an increase in the accumulation of omst, without aflatoxin synthesis. when radiolabeled [14c]omst was fed to resting mycelia of a non-aflatoxin-, non-st-, and non-omst-producing mutant of a. parasiticus avn-1 (srrc 163), 14c-labeled aflatoxins b1 and g1 were produced; 10 nmol ...19873111363
improved method of screening for aflatoxin with a coconut agar medium.nine isolates of aspergillus flavus and aspergillus parasiticus were screened for aflatoxin production on a coconut extract agar medium. aflatoxin-producing colonies were detected under long-wave uv light (365 nm) by blue fluorescence on the reverse side after 2 to 5 days of growth. aflatoxin production was verified by chemical analysis. several types of shredded coconut available in the united states were tested and found to be satisfactory. no additives were required. various parameters affect ...19873116928
appearance of enzyme activities catalyzing conversion of sterigmatocystin to aflatoxin b1 in late-growth-phase aspergillus parasiticus cultures.two activities involved in terminal pathway conversion of sterigmatocystin to aflatoxin b1 were isolated from an aflatoxin-nonproducing mutant of aspergillus parasiticus (avn-1), and the time course of appearance of the activities in culture was determined. subcellular fractionation of fungal mycelia resolved the two activities into a postmicrosomal activity which catalyzed conversion of sterigmatocystin to o-methylsterigmatocystin and a microsomal activity which converted o-methylsterigmatocyst ...19873116930
[culture of aspergillus parasiticus in apple juice. ii. the effect of butylhydroxyanisole (bha) and butylhydroxytoluol (bht) on fungal growth and aflatoxin biosynthesis].aspergillus parasiticus (nrrl 2999) was incubated in apple juice (from syrup), quiescently at 25 degrees c for up to 15 days in the presence of butylated hydroxyanisole (bha) or butylated hydroxytoluene (bht) at concentrations of 100, 200, 300, or 400 mg/l. mycelial dry weight, ph and concentration of aflatoxin b1 and g1 were measured every 3 days with the initial ph of 2.5 remaining unchanged in all samples. bha suppressed fungal growth and toxin accumulation during the observed incubation peri ...19873125696
[ability of bentonite and natural zeolite to adsorb aflatoxin from liquid media].the adsorption of aflatoxin (af) b1, contained in aqueous medium or in synthetic medium left after the cultivation of aspergillus parasiticus nrrl 2999, was studied in two samples of bentonite, two samples of natural zeolite, and three kinds of adsorption coal added to water, to saline, to the blood serum of pigs, to the stomach fluid of pigs or rumen fluid of cows at concentrations of 5 to 50 mg per litre. unlike retinol-propionate and beta-carotene, af was readily adsorbable in vitro. the init ...19892547262
reversal of aflatoxin induced liver damage by turmeric and curcumin.the effect of certain food additives on aflatoxin production by aspergillus parasiticus has been studied in vitro. extracts of turmeric (curcuma longa), garlic (allium sativum) and asafoetida (ferula asafoetida) inhibited the aflatoxin production considerably (more than 90%) at concentrations of 5-10 mg/ml. similar results were also seen using butylated hydroxytoluene, butylated hydroxyanisole and ellagic acid at concentration 0.1 mm. curcumin, the antioxidant principle from curcuma longa did no ...19921394115
cloning of a gene associated with aflatoxin b1 biosynthesis in aspergillus parasiticus.a cosmid library was constructed by inserting genomic dna isolated from a wild-type aflatoxin-producing strain of aspergillus parasiticus (su-1) into a cosmid vector containing an homologous nitrate reductase (niad) gene as a selectable marker. one cosmid was isolated which complemented an aflatoxin-deficient, nitrate-nonutilizing mutant strain, a. parasiticus b62 (nor-1, niad), to aflatoxin production. deletion and complementation analyses showed that a 1.7 kb bglii-sphi dna fragment isolated f ...19921563048
the affinity purification and characterization of a dehydrogenase from aspergillus parasiticus involved in aflatoxin b1 biosynthesis.a two step scheme has been developed for the purification of a dehydrogenase from mycelia of 84 hours old aspergillus parasiticus (1-11-105 wh 1), which catalyzes the conversion of norsolorinic acid (na) to averantin (avn). the dehydrogenase was purified from cell-free extracts using reactive green 19-agarose and norsolorinic acid-agarose affinity chromatography. the latter affinity matrix was synthesised by attaching norsolorinic acid to omega-aminohexylagarose. the purified protein was shown t ...19911798691
biosynthetic origin of aflatoxin g1: confirmation of sterigmatocystin and lack of confirmation of aflatoxin b1 as precursors.the origin of aflatoxin g1 was studied using mutant strains of aspergillus parasiticus blocked early in the pathway and by tracing 14c-labelled aflatoxin b1 (afb1) in wild-type a. flavus and a. parasiticus strains. sterigmatocystin (st) was a precursor of afb1, afg1 and afg2 in the four mutants examined. the identity of afg1 was confirmed by mass spectrometry. no evidence for conversion of afb1 to afg1 was found. a rigorously controlled study of conversions of radioactivity based on preparative ...19883141572
inactivation of aflatoxin b1 in corn meal, copra meal and peanuts by chlorine gas treatment.more than 75% degradation of aflatoxin b1 (afb1) was achieved after treatment of afb1-spiked corn meal, spiked copra meal (the residue of the kiln-dried coconut kernels after mechanical expulsion of oil) and peanuts artificially infected with aspergillus parasiticus, with 11, 16 and 35 mg chlorine gas per g meal or peanuts, respectively. at these chlorine gas treatment levels, extension of the exposure period of the corn meal and copra meal beyond 2.5 hr, and the peanuts beyond 1 day, did not in ...19911900253
isolation and characterization of aspergillus parasiticus mutants with impaired aflatoxin production by a novel tip culture method.a convenient procedure consisting of uv photography (k. yabe, y. ando, m. ito, and n. terakado, appl. environ. microbiol. 53:230-234, 1987) and a tip culture method has been devised for the isolation and characterization of aspergillus parasiticus mutants relating to aflatoxin production. with the latter procedure, the production of aflatoxins excreted into the culture medium and precursors in the mycelium were easily measured quantitatively or semiquantitatively. a total of 38 mutants in which ...19883178213
diminution of aflatoxicosis in growing chickens by the dietary addition of a hydrated, sodium calcium aluminosilicate.the amelioration of aflatoxicosis in broiler and leghorn chickens was examined by feeding a hydrated, sodium calcium aluminosilicate (hscas) or activated charcoal. in three experiments, hscas or activated charcoal at a concentration of .5% of the total diet were incorporated into diets for broiler and leghorn chicks containing either no added, purified aflatoxin b1 (afb1), 7.5 mg of afb1 per kg, or 5 mg of aflatoxin (af) per kg (produced by aspergillus parasiticus on rice). compared to the contr ...19901973286
transformation of aspergillus parasiticus with a homologous gene (pyrg) involved in pyrimidine biosynthesis.the lack of efficient transformation methods for aflatoxigenic aspergillus parasiticus has been a major constraint for the study of aflatoxin biosynthesis at the genetic level. a transformation system with efficiencies of 30 to 50 stable transformants per microgram of dna was developed for a. parasiticus by using the homologous pyrg gene. the pyrg gene from a. parasiticus was isolated by in situ plaque hybridization of a lambda genomic dna library. uridine auxotrophs of a. parasiticus atcc 36537 ...19902176447
development of a homologous transformation system for aspergillus parasiticus with the gene encoding nitrate reductase.the nitrate reductase structural gene (niad) and an niad mutant strain were isolated from aspergillus parasiticus and used to develop a homologous transformation system. a transformation frequency of 110 to 120 transformants per microgram linear dna was obtained with the 10.9 kb plasmid psl82, which contained the niad gene of a. parasiticus. plasmid psl82 was also capable of complementing aspergillus nidulans fgsc a691, a niad mutant, though at lower frequencies. southern hybridization analyses ...19902277647
water activity influence on aflatoxin accumulation in corn.the influence of water activity on the production of b1, b2, g1 and g2 aflatoxins in corn has been examined. viable corn kernels were conditioned at three water activity levels (0.87, 0.90 and 0.97) and inoculated with aspergillus parasiticus at 30 degrees c. aflatoxin accumulation was determined at selected times by thin-layer chromatography. for the strain used total aflatoxin accumulation was greater at water activity 0.90 than at 0.87 and 0.97 for the incubation times studied.19883275305
evidence for de novo synthesis of an aflatoxin pathway methyltransferase near the cessation of active growth and the onset of aflatoxin biosynthesis in aspergillus parasiticus mycelia.the accumulation of both activity and protein of a methyltransferase (mtase) from aspergillus parasiticus, which catalyzes conversion of sterigmatocystin to o-methylsterigmatocystin in the aflatoxin pathway, was detected in fungal mycelia slightly before the onset of aflatoxin biosynthesis in the same cultures. mtase protein was identified in mycelial postmicrosomal (soluble protein) fractions by electrophoresis and subsequent immunoblotting using antiserum raised against purified mtase protein; ...19902334871
conversion of versiconal acetate to versiconal and versicolorin c in extracts from aspergillus parasiticus.the primary product of hydrolysis of versiconal acetate catalyzed by porcine liver esterase and the 35-70% ammonium sulfate fraction from a soluble extract from mycelia of aspergillus parasiticus was versiconal. versiconal was stable at neutral ph for several hours and was rapidly converted to versicolorin c by treatment with 0.4 m hcl. the addition of nadph to the 35-70% ammonium sulfate fraction resulted in conversion of versiconal acetate to both versiconal and versicolorin c. the conversion ...19902352549
isolation and characterization of a gene from aspergillus parasiticus associated with the conversion of versicolorin a to sterigmatocystin in aflatoxin biosynthesis.dna isolated from the wild-type aflatoxin-producing (afl+) fungus aspergillus parasiticus nrrl 5862 was used to construct a cosmid genomic dna library employing the homologous gene (pyrg) encoding orotidine monophosphate decarboxylase for selection of fungal transformants. the cosmid library was transformed into an afl- mutant, a. parasiticus cs10 (ver-1 wh-1 pyrg), deficient in the conversion of the aflatoxin biosynthetic intermediate versicolorin a to sterigmatocystin. one pyrg+ afl+ transform ...19921339261
occurrence of aflatoxins and aflatoxin-producing moulds in fresh and processed meat in egypt.a survey was carried out to detect aflatoxins and isolate aflatoxigenic moulds contaminating fresh and processed meat products. the fungal contamination was examined in 215 samples of fresh and processed meat products and 130 samples of spices used in the meat industry collected from different local companies in cairo, egypt. processed meat products such as beefburger, hot-dog, kubeba, sausage, luncheon meat had the highest count of moulds as compared with fresh and canned meat. out of 150 sampl ...19911778268
interaction of water activity and temperature on aflatoxin production by aspergillus flavus and a. parasiticus in irradiated maize seeds.the effects of aw (0.90, 0.95, 0.98) and temperature (25 degrees c, 30 degrees c, 35 degrees c) on aflatoxin production by aspergillus flavus and aspergillus parasiticus growing on irradiated maize seeds, were examined. highest levels of aflatoxin were produced by a. parasitious at 25 degrees c and 0.98 aw and by a. flavus at 30 degrees c at 0.95 and 0.98 aw. at 0.90 aw toxin production was consistently low for both species at all temperatures. temperature cycling of a. flavus between 25 degrees ...19911812020
color mutants of aspergillus flavus and aspergillus parasiticus in a study of preharvest invasion of peanuts.a comparison of the invasion of flowers, aerial pegs, and kernels by wild-type and mutant strains of aspergillus flavus or a. parasiticus along with aflatoxin analyses of kernels from different drought treatments have supported the hypothesis that preharvest contamination with aflatoxin originates mainly from the soil. evidence in support of soil invasion as opposed to aerial invasion was the following. a greater percentage of invasion of kernels rather than flower or aerial pegs by either wild- ...19863098167
aflatoxins in sunflower seeds: effect of zinc in aflatoxin production by two strains of aspergillus parasiticus.growth and aflatoxin production by aspergillus parasiticus nrrl 2999 and aspergillus parasiticus rc 12 were studied both in sunflower seed and a synthetic culture medium (with and without zinc enrichment). on a synthetic culture medium the strains behaved in different ways according to the zinc concentration. in sunflower seed medium the influence of zinc was not so evident. thus the results show that the influence of zinc is not the same for different strains and substrates.19873657905
conversion of dihydro-o-methylsterigmatocystin to aflatoxin b2 by aspergillus parasiticus.dihydro-o-methylsterigmatocystin (dhomst) was identified in cultures of aspergillus parasiticus srrc 2043, an aflatoxin (af) non-producer, by comparison of its mass spectrum to that of authentic dhomst. in addition to dhomst, srrc 2043 is known to produce two other chemically related compounds in culture: o-methylsterigmatocystin (omst) which is an afb1 precursor and a hydrated-vinyl ether analogue of omst (homst) which is an afb2 precursor. in the present study, dhomst also was shown to be an a ...19892730159
effect of peanut tannin extracts on growth of aspergillus parasiticus and aflatoxin production.twenty-three peanut (arachis hypogaea l.) genotypes were evaluated for kernel resistance to aspergillus parasiticus spear. colonization and aflatoxin contamination when incubated under high relative humidity. also, tannin-containing extracts from kernel coats (testae) and cotyledons of these genotypes were prepared and tested for their effect on a. parasiticus growth and aflatoxin production in vitro. the lowest degree of colonization, less than 30%, was noted in kernels from the genotypes, toal ...19902388679
enzymes in aflatoxin b1 biosynthesis: strategies for identifying pertinent genes.recent work on the aflatoxin biosynthetic pathway is reviewed, with special emphasis on the enzymes of the late stages of the pathway involving conversion of sterigmatocystin (st) to aflatoxin b1 (afb1) through an o-methylsterigmatocystin intermediate. two enzyme activities were discovered in subcellular fractions of cell-free extracts of a mutant strain of aspergillus parasiticus (srrc 163): 1) a post-microsomal methyltransferase (mt) catalyzed conversion of st to omst, and 2) a microsomal-asso ...19892515439
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