Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Aspergillus parasiticus  (18)
  • 1
    ISSN: 1573-0832
    Keywords: Aspergillus parasiticus ; derivatives ; specificity ; sterigmatocystin ; synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Seven alkyl and aryl homologues of O-methylsterigmatocystin (OMST) were synthesised and fed in separate experiments to a mutant of Aspergillus parasiticus capable of converting sterigmatocystin (ST) to aflatoxin B1 (AFB1). Their conversion to AFB1 was followed over a time period and it was found that O-propylsterigmatocystin (OPRST) was converted to AFB1 more rapidly than O-ethylsterigmatocystin (OEST) or OMST or ST itself. The aryl derivative O-benzoylsterigmatocystin (OBzST) was converted at the slowest rate. These results show that alkyl and aryl homologues of OMST may be converted to AFB1, suggesting that the methylation of ST is not an absolute requirement for its conversion to AFB1. It seems likely that whatever enzyme(s) are involved in this process exhibit relative specificity. As to whether alkylation of ST is an obligatory step in AFB1 biosynthesis is neither supported nor disproved as the fungal cells used are presumably capable of methylating ST. The fact that the propyl derivative showed fastest conversion is not necessarily significant as this may be due to faster diffusion of the least polar of the derivatives through the cell membrane.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 2
    ISSN: 1573-0832
    Keywords: Aflatoxin B1 ; zearalenone ; deoxynivalenol ; irradiated maize grain ; Fusarium graminearum ; Aspergillus parasiticus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The influence of inoculum size in the production of aflatoxin B1 (AFB1), zearalenone (ZEN) and deoxynivalenol (DON) was determined when Aspergillus parasiticus NRRL 3000 and Fusarium graminearum ITEM 124 were cultured alone and in pairs on irradiated corn kernels at 28 °C and 0.97 water activity (aw). The highest levels of AFB1 produced by A. parasiticus were produced at the lowest levels of the inoculum (103 spores/ml). No significant differences were observed in ZEN and DON production at any inoculum level during the experimental period. When A. parasiticus was co-inoculated with F. graminearum both to the same inocula (106 spores/ml), AFB1 inhibition percentage were 60, 72 and 56% at 10, 20 and 35 days of incubation respectively, while at 106 spores/ml the percentages of inhibition were 34, 84 and 93% at 10, 20 and 35 days. In the mixture cultures A. parasiticus 103 × F. graminearum 106 spores/ml the percentage of inhibition of AFB1 oscillated in 99% during all the incubation. In the interaction A. parasiticus 106 spores/ml × F. graminearum 103 spores/ml the accumulation of AFB1 decreased in 80, 94 and 86% at 10, 20 and 35 days of incubation respectively. In single culture F. graminearum was inoculated with 103 or 106 spores/ml and the highest levels of ZEN and DON were detected at 35 days of incubation. The levels oscillated in 538–622 μg/kg for ZEN and 870–834 μg/kg for DON respectively. In paired cultures there were no significant differences in the levels regardless of the spore concentrations during the incubation time.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 3
    ISSN: 1573-0832
    Keywords: aflatoxin ; sunflower seeds ; Aspergillus parasiticus ; Alternaria ; alternariol ; alternariol monomethyl ether ; interaction of microorganisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 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 °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 infected from the 7th day. When Aspergillus parasiticus and Alternaria alternata were simultaneously inoculated the infection level of the seeds was 100% for Aspergillus parasiticus following 7 days of inoculation and 0% for Alternaria alternata. After the 14th day of inoculation there was no significant difference in the infection percentage of both strains (approximately 80% of each one). As far as toxin production is concerned a remarkable decrease was observed when seeds were inoculated with both strains simultaneously. In accordance to the results, Alternaria alternata would not compete with Aspergillus parasiticus in colonization of seeds but would either degrade the aflatoxins by Aspergillus parasiticus or compete for aflatoxin biosynthesis precursors. Alternaria alternata could also secrete some substance that specifically inhibits aflatoxin synthesis.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 4
    ISSN: 1573-0832
    Keywords: Peanut ; groundnut ; aflatoxin ; resistance ; testae ; tannins ; Aspergillus parasiticus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 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, Toalson x UF 73-4022 (selections TX-798731 and TX-798736), A72118, SN 55-437, PI337409, and Florunner. Genotypes with low levels of colonization also had the lowest aflatoxin contamination. The coefficient of correlation between infection frequency and aflatoxin contamination was 0.66. Higher levels of tannins were detected in the testae (23.9–97.2 mg g tissue) compared to the cotyledons (0.17–0.82 mg g tissue). Some of the methanol-extracted and water-soluble tannin extracts from testae and cotyledons, when incorporated in yeast extract sucrose liquid medium (100 mg l), significantly inhibited A. parasiticus growth and reduced the levels of aflatoxin produced. There was no overall correlation between the peanut genotypes and the influence of tannin extracts on A. parasiticus growth and aflatoxin production. However, correlations were higher for specific genotypes. For example, the coefficient of correlation between the ability of tannin extracts from testae of genotypes PI337409 and TX-798736 to inhibit aflatoxin production was 0.93 and 0.85 respectively.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 5
    ISSN: 1573-0832
    Keywords: Aspergillus parasiticus ; averantin ; norsolorinic acid ; secondary metabolic enzyme
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The activity of the enzyme responsible for the conversion of norsolorinic acid to averantin was studied in two strains of Aspergillus parasiticus. Cell-free extracts of the enzyme were purified from different aged mycelia and little activity was found prior to 24 hours after inoculation but this quickly reached a maximum at 48 hours and declined thereafter. Both strains of A. parasiticus, one in aflatoxin producing strain, the other a versicolorin A accumulating mutant, showed this trend. It was concluded that the enzyme responsible for this conversion was a secondary metabolic enzyme and was distinct from alcohol and mannitol dehydrogenases.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 6
    ISSN: 1573-0832
    Keywords: corn genotypes ; corn meal ; Aspergillus flavus ; Aspergillus parasiticus ; aflatoxin B1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract A study has been carried out in Argentina on samples of corn genotypes from a breeding station as well as in commercially available corn meal. All samples were analyzed for fungal infection and aflatoxin B1.Mycological analysis of corn genotypes showed the presence of three principal genera of filamentous fungi Fusarium (100%), Penicillium (67%) and Aspergillus (60%). In the genus Fusarium three species were identified, F. moniliforme (42%), F. nygamai (56%) andF. proliferatum (1.8%). Eight species ofPenicillium were identified, the predominant species isolated were P. minioluteum, P. funiculosum and P. variabile. In the genus ranked third in isolation frequency, two species were identified, A. flavus and A. parasiticus, the percentage of infection was 78% and 21%, respectively. Only one corn genotype was contaminated with aflatoxin B1 at a level of 5 ppb. The cornmeal samples showed great differences in fungal contamination, the values ranging from 1 × 101 to 7 × 105 cfu g−1. Fusarium (68%), Aspergillus (35%) and Penicillium (21%) were the most frequent genera isolated. Among the genus, Aspergillus, A. parasiticus (38%) was the most frequent species isolated. All the samples of corn meal were negative to aflatoxin B1. These results indicate a low degree of human exposure to aflatoxins in Argentina through the ingestion of maize or corn meal.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 7
    ISSN: 1573-0832
    Keywords: Aflatoxin ; aflR ; Aspergillus parasiticus ; repressor ; sclerotia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Regulation of aflatoxin (AF) biosynthesis likely involves a complex interplay of positive- and negative-acting factors that are affected by physiological cues responsive to internal and external stimuli. These factors, presumably, modulate the expression of the AF pathway-specific regulatory gene, aflR, whose product, AFLR, a zinc cluster transcription factor, then turns on or off the transcription of other AF genes. To determine if the AFLR carboxyl region (AFLRC) interacts with positive-or negative-acting proteins, we fused the Aspergillus parasiticus aflR carboxyl coding region(aflRC) to the promoter of A. parasiticusnitrite reductase gene (niiA(p)::aflRC), and transformed it into A. parasiticus SRRC 2043. Transformants that contained two copies of niiA(p)::aflRC, one at the niaD locus and another at the aflR locus, over produced AF precursors independent of the nitrogen source. The higher copy number of the integrated niiA(p)::aflRC correlated with increased production of AF precursors by the transformants as well as increased expression of both aflRC and native aflR in potato dextrose broth and A & M medium. Since aflRC does not encode a DNA-binding domain, the expressed AFLRC should not bind to the promoters of AF pathway genes and affect transcription directly. The results are consistent with AFLRC titrating out a putative repressor that interacts with AFLR under different growth conditions and modulates AF biosynthesis. This interaction also indirectly affects sclerotial development.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 8
    ISSN: 1573-0832
    Keywords: Aflatoxins ; Versicolorins ; Aspergillus parasiticus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 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 M) inhibited secondary biosynthesis and low concentrations of acetone (0.1, 0.025 and 0.01 M) stimulated secondary biosynthesis of aflatoxins and versicolorin pigments.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 9
    ISSN: 1573-0832
    Keywords: Aspergillus parasiticus ; moisture content ; mixed feeds ; aflatoxins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Minimal moisture content for growth and aflatoxin production by Aspergillus parasiticus in mixed feeds was studied. Minimal moisture content for growth is 16.51%+/−0.45. Very low amounts of aflatoxins are accumulated at days 1 or 2 after the growth started when the initial moisture content of the mixed feed was 17% or lower; on the other hand, significant amounts of aflatoxin are detected when it was 18% or higher.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
  • 10
    ISSN: 1573-0832
    Keywords: aflatoxin ; sunflower seeds ; Aspergillus parasiticus ; zinc
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract 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.
    Type of Medium: Electronic Resource
    Signatur Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...