Fate of the methyl group during the conversion of sterigmatocystin into O-methylsterigmatocystin and aflatoxin B1 by cell-free preparations of Aspergillus parasiticus

The effect of two inhibitors on the formation of aflatoxin B1 synthetase activity in strain NRRL 2999 Aspergillus parasiticus has been studied. Aflatoxin B1 synthesizing activity was measured in vivo by incorporation of the 14C-methionine methyl group into aflatoxin B1. Cycloheximide at a concentration of 150 μg/ml blocks protein synthesis completely. If addition of cycloheximide is made before B1 synthetase appears, no activity accumulates; if added during accumulation, activity is frozen at the level reached at the time of addition. The cycloheximide effect is reversible since morphogenesis, total protein synthesis, and aflatoxin B1 synthetase activity all resume after removal of the inhibitor.DL-p-Fluorophenylalanine partially inhibits aflatoxin B1 synthesis in vivo; however, its effect upon macromolecular synthesis is incomplete even at high concentration levels. Once formed, the aflatoxin synthetase appears to maintain B1 synthesis when further protein synthesis is blocked; i.e., it is not rapidly degraded.

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Production of aflatoxins and aflatoxicols by Aspergillus flavus and Aspergillus parasiticus and metabolism of aflatoxin B1 by aflatoxin-non-producing Aspergillus flavus.

Eisei kagaku ◽

10.1248/jhs1956.37.107 ◽

1991 ◽

Vol 37 (2) ◽

pp. 107-116 ◽

Cited By ~ 6

Author(s):

MITSUO NAKAZATO ◽

SATOSHI MOROZUMI ◽

KAZUO SAITO ◽

KENJI FUJINUMA ◽

TAICHIRO NISHIMA ◽

...

Keyword(s):

Aspergillus Flavus ◽

Aflatoxin B1 ◽

Aspergillus Parasiticus

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Effects of Potassium Sorbate on Growth and Aflatoxin Production by Aspergillus parasiticus and Aspergillus flavus1

Journal of Food Protection ◽

10.4315/0362-028x-46.11.940 ◽

1983 ◽

Vol 46 (11) ◽

pp. 940-942 ◽

Cited By ~ 15

Author(s):

LLOYD B. BULLERMAN

Keyword(s):

Aspergillus Flavus ◽

Yeast Extract ◽

Aflatoxin B1 ◽

Spore Germination ◽

Mycelial Growth ◽

Aspergillus Parasiticus ◽

Aflatoxin Production ◽

Potassium Sorbate ◽

Mycelial Mass ◽

Yeast Extract Sucrose

Growth and aflatoxin production by selected strains of Aspergillus parasiticus and Aspergillus flavus in the presence of potassium sorbate at 12°C were studied. Potassium sorbate at 0.05, 0.10 and 0.15% delayed or prevented spore germination and initiation of growth, and slowed growth of these organisms in yeast-extract sucrose broth at 12°C. Increasing concentrations of sorbate caused more variation in the amount of total mycelial growth and generally resulted in a decrease in total mycelial mass. Potassium sorbate also greatly reduced or prevented production of aflatoxin B1 by A. parasiticus and A. flavus for up to 70 d at 12°C. At 0.10 and 0.15% of sorbate, aflatoxin production was essentially eliminated. A 0.05% sorbate, aflatoxin production was greatly decreased in A. flavus over the control, but only slightly decreased in A. parasiticus.

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Preparation of 14C-Labeled Aflatoxin B1

Journal of AOAC INTERNATIONAL ◽

10.1093/jaoac/56.3.643 ◽

1973 ◽

Vol 56 (3) ◽

pp. 643-646

Author(s):

Grant L Schoenhard ◽

Russell O Sinnhuber ◽

Donald J Lee

Keyword(s):

Trace Metals ◽

Primary Culture ◽

Silica Gel ◽

Aflatoxin B1 ◽

Aspergillus Parasiticus ◽

Specific Activity ◽

Ultraviolet Spectrum ◽

Reference Standard ◽

Chemical Purity ◽

Chloroform Methanol

Abstract A successful method to obtain 14C-labeled aflatoxin B1 from Aspergillus parasiticus ATCC 15517 was developed. The nitrogen-free resting culture contained mycelia from a 72 hr primary culture, 0.02M glucose, 0.005M (1 mCi/mmole) acetate-1-14C, salts, and trace metals. It was incubated 12 hr at 30°C. Aflatoxin B1-14C was isolated from chloroform extracts of the resting culture by column chromatography on silica gel H eluted under pressure with a continuous gradient of chloroform to chloroform-methanol (98+2). The ultraviolet spectrum of the 14C-labeled aflatoxin was examined. The ratios of the absorbances at 220/265 and 362/265 nm compared to established values and a reference standard were used as criteria of chemical purity. Label integrity was verified by chromatography, hydrogenation to the tetrahydrodeoxoaflatoxin B1, and conversion to the hemiacetal and the epimeric acetates. After purification, 1.37 mg 14C-labeled aflatoxin B1 of specific activity 744 μCi/mmole was obtained from 2 mCi acetate-1-14C of specific activity 1 mCi/mmole.

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Individual reaction requirements of two enzyme activities, isolated from Aspergillus parasiticus, which together catalyze conversion of sterigmatocystin to aflatoxin B1

Canadian Journal of Microbiology ◽

10.1139/m87-193 ◽

1987 ◽

Vol 33 (12) ◽

pp. 1108-1112 ◽

Cited By ~ 15

Author(s):

Thomas E. Cleveland ◽

Deepak Bhatnagar

Keyword(s):

Aflatoxin B1 ◽

Enzyme Activities ◽

Microsomal Fraction ◽

Aspergillus Parasiticus ◽

Heat Treated ◽

Individual Reaction ◽

Aflatoxin B

Individual reaction requirements were determined for each of two enzyme activities present in Aspergillus parasiticus mycelia which together catalyze conversion of sterigmatocystin (ST) to aflatoxin B1 (AFB1). A postmicrosomal activity (PMA) catalyzed conversion of ST to O-methylsterigmatocystin (OMST) and a microsomal activity (MA) catalyzed conversion of OMST to AFB1. PMA was stimulated two- to three-fold in the presence of S-adenosylmethionine. Addition of NADPH promoted the maximum MA; this activity was not detected when FAD, FMN, NAD, or NADH were utilized individually as cofactors in reaction mixtures. A substantial amount (62%) of MA was lost during isolation of the microsomal fraction, but the activity was completely restored by reconstitution with a heat-treated (100 °C) postmicrosomal fraction. The reaction catalyzed by MA was optimum at pH 7.0 and at 17–23 °C, whereas the PMA reaction was optimum at pH 8.0–8.5 and at 35–40 °C. Apparent Km values of approximately 2.6 × 10−6 M (for ST) and 6.6 × 10−7 M (for OMST) were determined for PMA and MA, respectively.

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Growth and Aflatoxin Production by Aspergillus parasiticus NRRL 2999 in the Presence of Acetic or Propionic Acid and at Different Initial pH Values

Journal of Food Protection ◽

10.4315/0362-028x-50.11.909 ◽

1987 ◽

Vol 50 (11) ◽

pp. 909-914 ◽

Cited By ~ 14

Author(s):

GULAM RUSUL ◽

FATHY E. EL-GAZZAR ◽

ELMER H. MARTH

Keyword(s):

Acetic Acid ◽

Propionic Acid ◽

Aflatoxin B1 ◽

Maximum Concentration ◽

Aspergillus Parasiticus ◽

Dry Weight ◽

Aflatoxin Production ◽

Lag Phase ◽

Significant Difference ◽

Initial Ph

Experiments were done to determine effects of different concentrations of acetic or propionic acid in a glucose-yeast extract-salts medium with an initial pH value of 4,5 or 5.5 on growth and aflatoxin production by Aspergillus parasiticus NRRL 2999. Amounts of aflatoxin were measured with reversed-phase high-performance liquid chromatography. The maximum concentration of acetic or propionic acid that permitted growth at an initial pH of 5.5 was 1% after 7 d of incubation and 0.25% after 3 d of incubation, respectively. When the initial pH of the medium was 4.5, the maximum concentration of acetic or propionic acid that permitted growth was 0.25 or 0.1%, respectively. There was no significant difference (p>0.05) in amount of mycelial (dry weight) produced by cultures in the presence of 0.0, 0.25, 0.50 or 0.75% acetic acid. Amounts of aflatoxin B1 and G1 produced decreased with an increasing concentration of acetic acid. Increasing concentrations of propionic acid caused a decrease in the amount of mycelial dry weight and aflatoxin produced by cultures growing in the medium with an initial pH of 5.5. At an initial pH of 4.5 mycelial growth was slow and at 3 d of incubation amounts of aflatoxin B1 and G1 produced were reduced as concentrations of acetic acid increased. This also was true for propionic acid in the medium with an initial pH of 4.5. Cultures with an extended lag phase in the presence of acetic or propionic acid overcame this and then produced large amounts of aflatoxin B1 and G1 at 7 and 10 d of incubation.

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Inhibition of aflatoxin B1, B2, G1 and G2 production by Aspergillus parasiticus in nuts using yellow and oriental mustard flours

Food Control ◽

10.1016/j.foodcont.2014.07.008 ◽

2015 ◽

Vol 47 ◽

pp. 154-160 ◽

Cited By ~ 29

Author(s):

C. Hontanaya ◽

G. Meca ◽

F.B. Luciano ◽

J. Mañes ◽

G. Font

Keyword(s):

Aflatoxin B1 ◽

Aspergillus Parasiticus ◽

Oriental Mustard

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PRODUCTION OF AFLATOXIN IN CONCENTRATED AND DILUTED GRAPEFRUIT JUICE1

Journal of Milk and Food Technology ◽

10.4315/0022-2747-37.7.395 ◽

1974 ◽

Vol 37 (7) ◽

pp. 395-398 ◽

Cited By ~ 3

Author(s):

G. G. Alderman ◽

E. H. Marth

Keyword(s):

Aspergillus Flavus ◽

Aflatoxin B1 ◽

Grapefruit Juice ◽

Aspergillus Parasiticus ◽

Soluble Solids ◽

Soluble Solids Content ◽

Initial Value ◽

Visible Growth ◽

Solids Content

Commercial concentrated and diluted (1:1, 1:2, 1:3; juice: water) steamed grapefruit juice was inoculated with known aflatoxigenic aspergilli and sampled after 10 and 14 days of incubation at 28 C. When Aspergillus flavus grew in juice, most aflatoxin B1 (0.211 μg/ml appeared in concentrated juice and least (0.013 μg/ml) in single strength juice. Juices diluted 1:1 and 1:2 yielded 0.078 and 0.020 μg B1/ml, respectively. Results were more striking when Aspergillus parasiticus grew in samples of juice. After 10 days, amounts of aflatoxin B1 in concentrated juice and in concentrated juice diluted 1:1, 1:2, and 1:3 were 7.5, 1.59, 0.69, and 0.56 μg/ml, respectively. Aflatoxins B2, G1, and G2 were also produced and greatest amounts also developed in concentrated juice. Amounts of these toxins decreased markedly when the percentage of soluble solids in the juices decreased. Fourteen instead of 10 days of incubation resulted in increases in the amount of each toxin in concentrated juice and in concentrated juice diluted 1:1. Although the greatest amount of aflatoxin occurred in concentrated juice, appearance of visible growth and onset of sporulation by the molds was slower in this than in diluted juices. The pH of the concentrated juice did not change appreciably after 10 and 14 days of incubation, but the pH of diluted juices rose progressively from the initial value as the percent soluble solids content in the juice decreased.

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