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PubMed1988

Experimental aflatoxin production in home-made yoghurt.

Fungal growth and aflatoxin production by an aflatoxigenic strain during the manufacture of yoghurt are described. This completes previous studies which show that yoghurt may be a good substrate for aflatoxin production. Two factors were of special interest: (a) the temperature of the elaboration process (45 degrees C) and (b) the effect of lactic bacteria. Either during the elaboration of yoghurt or during its cooling from 45 degrees C to 4 degrees C, the necessary conditions required to start fungal growth are given; these are adequate enough for the synthesis of small quantities of aflatoxins. However our results do not clearly show that lactic bacteria have an influence on fungal growth and aflatoxin production.

Aflatoxins↗

PubMed1987

Effects of gamma irradiation on aflatoxins.

The effects of gamma irradiation on a mixture of aflatoxins B1, B2, G1, G2 were studied. Standard solutions of A and B were irradiated at 5, 10, and 20 kGy in a solution of water/DMSO (9 + 1, v/v) by using a 137Cs source. The control (0 kGy) and irradiated samples were subjected to RP-HPLC analyses with methanol/water (4 + 5, v/v) as the mobile phase. Aflatoxin B1 (AFB1) was the most radio-sensitive of the four compounds. The radiosensitivity of the other aflatoxins, was in increasing order: G2, B2, G1. Only about 5% of AFB1 remained after irradiation of solution A at 5 kGy. When the concentration of solution B was increased two-fold, trace amounts of AFB1 remained after irradiation doses of 10 and 20 kGy. Irradiation was found to be suitable for the destruction of aflatoxins in solution.

Aflatoxins↗

PubMed1993

Survey of aflatoxins and ochratoxin A in stored tubers of Cyperus esculentus L.

The mold incidence, moisture contents, pH and levels of mycotoxins (aflatoxins B1, G1 and ochratoxin A) on/of/in rootstock snack (tubers of Cyperus esculentus L.) samples were monitored during a 150-day storage period. Whereas the mold incidence, moisture and mycotoxin levels increased with storage time, the pH declined during the same period. Altogether, 12 fungal species, mostly toxigenic, including Aspergillus flavus, A. parasiticus and A. ochraceus were isolated. At collection period only 3 of the 9 snack samples analysed contained trace amounts of aflatoxins. By 120th day, all the 9 samples were contaminated and the average levels were 454 and 80 ppb for aflatoxin B1 and aflatoxin G1 respectively on the 150th day. Ochratoxin A was not detected before 120th day and then only at low levels, occurring in a maximum of four-samples and ranging between 10 and 80 ppb.

Aflatoxins↗

PubMed1976

Interaction of aflatoxin B1 with some biologically important substances.

The interaction of aflatoxin B1 with a number of biologically important substances has been investigated by spectrophotometric and fluorimetric techniques. The ultra-violet absorption of tryptophan, adenosine, RNA and DNA were altered by the addition of aflatoxin B1. Some amino-acids, purine and pyrimidine derivatives, bovine-serum albumin and DNA quenched the fluorescence of aflatoxin B1. Fluorescence polarization data suggested that the interaction of aflatoxin B1 with bovine-serum albumin was stronger than that with DNA.

Adenosine↗

PubMed1976

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. When the glucose-yeast extract medium was used, 3000 ppm of either oil were needed to achieve the same result. After 4 days at 28 degrees C, orange oil at 3500 ppm in either medium markedly inhibited mold growth (as evidenced by dry weight of mold mycelium) and aflatoxin production (only 14 and 1% of the amount normally produced in the juice and artificial medium, respectively). Higher concentrations of orange oil further reduced mold growth and aflatoxin production and also delayed the onset of sporulation, if it occurred. Although aflatoxin was detected in all samples, only 0.2 to 0.5% of the amount found in controls (without the citrus oil) was present when the medium contained 7000 ppm orange oil. The mold consistently grew, albeit very poorly, on the glass at the liquid-atmosphere interface even when the substrate contained a large amount of citrus oil.

Aflatoxins↗

PubMed1988

Growth and aflatoxin production by Aspergillus parasiticus in a medium at different pH values and with or without pimaricin.

A glucose-yeast extract-salt medium containing 0, 5, 7.5, 10, 15 or 20 micrograms pimaricin/ml with an initial pH of 3.5 or 5.5 was inoculated with Aspergillus parasiticus WB 108 and incubated at 15 degrees or 28 degrees C. The pH, weight of mycelium and amount of aflatoxin produced were determined after 3, 7, and 10 days and after 14, 21, and 30 days when incubation was at 28 degrees or 15 degrees C, respectively. Increasing the concentration of pimaricin in the medium with an initial pH of 5.5 decreased the amounts of aflatoxin B1 and G1 produced after 3 days of incubation. When the initial pH of the medium was 3.5, no growth or toxin production occurred after 3 days of incubation in the medium containing 7.5 micrograms or more of pimaricin/ml. The presence of 20 micrograms of pimaricin/ml inhibited growth and toxin production after 7 days of incubation. When cultures were incubated at 15 degrees C, there was a lag phase which extended from 9 to 16 days, and the amounts of aflatoxin produced decreased with an increasing concentration of pimaricin. Pimaricin did not completely inhibit the growth and aflatoxin production by A. parasiticus. Pimaricin, in combination with a low pH, low temperature or 4% or 6% NaCl, initially caused slow mycelial growth and low toxin production, but the mold overcame the inhibitory effects and produced substantial amounts of mycelium and toxin.

Aflatoxins↗

PubMed1977

[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 not have a significant influence on the aflatoxin values. Even storage of cheese (camembert and cottage cheese) in a 10% salt solution did not inhibit aflatoxin formation at 20 degrees C.

Aflatoxins↗

PubMed1992

A rapid, sensitive and economic method for the detection, quantification and confirmation of aflatoxins.

A rapid, sensitive and economic method for the detection, quantification and confirmation of aflatoxins is described. Aflatoxins B1, B2, G1, and G2, are extracted by methanol/water (85 + 15) and partitioned into methylene dichloride. The methylene dichloride solution is cleaned up on a polypropylene column, filled with 0.5 g silica gel 60. The aflatoxins are eluted with chloroform-acetone (90:10) and are detected using bidirectional thin-layer chromatography (TLC) with aluminium silica gel foil. The mean recovery of aflatoxins B1, B2, G1, and G2 in corn samples was 73, 78, 80, and 64%, respectively; the limit of detection was 0.5 micrograms/kg. The results can also be confirmed by derivative formation using trifluoroacetic acid on the TLC plate. The method has been applied to a wide range of foods with good results.

Aflatoxins↗

PubMed1977

Examination of fungal growth and aflatoxin production on marihuana.

Under favorable growth conditions, Aspergillus flavus and A. parasiticus produced aflatoxins on marihuana. Cultures of A. flavus ATCC 15548 produced both aflatoxin B1 (AFB1) and G1 (AFG1). The production of AFG1 was substantially greater than that of AFB1. Cultures of A. flavus NRRL 3251 and A. parasiticus NRRL 2999 produced only AFB1. All natural flora cultures tested negative for aflatoxins. No Aspergilli sporulations were observed in these cultures. In the cultures inoculated with known toxigenic fungi, the highest mean level for total aflatoxins was 8.7 microgram/g of medium. Marihuana appears not to yield large quantities of these mycotoxins but sufficient levels are present to be a potential health hazard for both the user and the forensic analyst who is in daily contact with such plant material. Careful processing, storage, and sanitation procedures should be maintained with marihuana. If these conditions are disregarded due to the illicit status of marihuana, the potential for mycotoxin contamination must be considered.

Aflatoxins↗

PubMed1980

Hormonal influences on chemical carcinogenesis: studies with the aflatoxin B1 hepatocarcinoma model in the rat.

The role of adrenocorticotropin, cortisol, and corticosterone on chemical carcinogenesis was investigated using the rat aflatoxin B1 hepatocarcinoma model. The animals were divided into untreated controls and various experimental groups receiving the carcinogen alone or the carcinogen with a hormone. Animals lost during the treatment period died mostly of massive hepatic necrosis. The results following 65 weeks of observation show that: (1) hormones decrease the toxicity of aflatoxin B1; (2) adrenocorticotropin possibly exerts its influence on aflatoxin B1 hepatocarcinogenesis through adrenal stimulation, and (3) in aflatoxin B1-adrenocorticotropin treated animals, hepatocellular carcinoma, cholangiocarcinoma, and malignant lymphoma may be observed.

Adenoma, Bile Duct↗

PubMed1994

Mycoflora and aflatoxins in a west African corn-groundnut based convenience food.

A total of 14 fungal species, mostly toxigenic, were isolated from 50 samples of 'donkwa' snack obtained from 16 producers. All of the isolates recorded substantial growth, though at varying rates, on the 2% snack agar provided. They also induced a reduction in the oil and an increase in free fatty acids of the substrate suggesting their participatory roles in deterioration. Most of the snack samples analysed contained initial amounts of aflatoxins above the 'safe' permissible level (30 ppb). The initial toxin levels increased substantially with storage time under 79.5, 89.5 and 100% ambient relative humidities but increased only slightly when samples were kept at 71% relative humidity. Almost constant toxin levels were recorded throughout the study period under 51% relative humidity. Accumulation of aflatoxin B1 in samples was most enhanced at 89.5% relative humidity. Comparatively, greater amounts of aflatoxin B1 accumulated under all conditions than the amounts recorded for aflatoxin G1.

Aflatoxins↗

PubMed1976

The response of dietary stressed Periplaneta americana to chronic intake of pure aflatoxin B.

In general these studies seem to indicate that adult male P. americana are not particularly sensitive, toxicologically, to aflatoxin B1, even when maintained on a marginally inadequate diet containing a low level of sucrose and no protein. Also they may be capable of detecting low levels of aflatoxin B1 in their diet (12 mug/ml) and seem not to concentrate aflatoxin B1 in their bodies. Even in dietary stressed conditions adult male American cockroaches showed a very limited potential as a bioassay organism for this toxin. Actually it appears that they may be quite resistant to the toxin. Currently there is no definite answer as to the advantages or disadvantages of insufficient dietary proteins or even carbohydrates providing protection against this toxin. The results show that the toxin would not be an effective cockroach-killing agent and thus could not serve as a bioassay system. However, this insect could serve as a model system in further investigating the mode of action and possible detoxification of aflatoxin B1.

Aflatoxins↗

PubMed1993

Influences of chemical fertilizers (in vitro) on aflatoxin and citrinin synthesis by two strains of aspergilli.

The selective effect of various levels of phosphate and nitrate (as fertilizers) on biosynthesis of aflatoxin by Aspergillus parasiticus var. globosus, and citrinin by A. terreus var. aureus was studied in defined culture medium. Phosphate at 35-175 mmol per 50 mL decreased aflatoxin production, but increased citrinin synthesis. Nitrate at 73-365 mmol per 50 mL stimulated the synthesis of aflatoxin but depressed that of citrinin. A rise in the levels of nitrate and phosphate led to a decrease in aflatoxin production, an increase in citrinin production and an accumulation of mycelial phosphate and nitrate contents.

Aflatoxins↗

PubMed1980

The relationship between Pleurotus ostreatus and Aspergillus flavus and the production of aflatoxin.

The relationship between Pleurotus ostreatus and Aspergillus flavus in common mixed culture on various substrates was investiaged. It was found that P. Ostreatus, similarly to some other higher fungi, can liquidate colonies of A. flavus. This fungus does not produce aflatoxin and chromatographically similar compounds. On straw, corn cobs, millet and wheat A. flavus produced aflatoxin after a 3-week cultivation. A subsequent cultivation of P. ostreatus led to detoxication of straw and corn cobs but millet and wheat were not detoxicated. Cultivation of P. osteatus in the presence of 40-100 micrograms of aflatoxin B1 per g substrate did not result in detoxication of the material even after 34 d but the results showed that the aflatoxin concentration decreased to about one-fourth of the added amount.

Aflatoxins↗

PubMed2006

Aspergillus oryzae strains with a large deletion of the aflatoxin biosynthetic homologous gene cluster differentiated by chromosomal breakage.

Recently we divided Aspergillus oryzae RIB strains into group 1, having seven aflatoxin biosynthesis homologous genes (aflT, nor-1, aflR, norA, avnA, verB, and vbs), and group 2, having three homologues (avnA, verB, and vbs). Here, partial aflatoxin homologous gene cluster of RIB62 from group 2 was sequenced and compared with that of RIB40 from group 1. RIB62 showed a large deletion upstream of ver-1 with more than half of the aflatoxin homologous gene cluster missing including aflR, a positive transcriptional regulatory gene. Adjacent to the deletion of the aflatoxin homologous gene cluster, RIB62 has a unique sequence of about 8 kb and a telomere. Southern analysis of A. oryzae RIB strains with four kinds of probe derived from the unique sequence of RIB62 showed that all group 2 strains have identical hybridizing signals. Polymerase chain reaction with specific primer set designed to amplify the junction between ver-1 and the unique sequence of RIB62 resulted in the same size of DNA fragment only from group 2 strains. Based on these results, we developed a useful genetic tool that distinguishes A. oryzae group 2 strains from the other groups' strains and propose that it might have differentiated from the ancestral strains due to chromosomal breakage.

Aflatoxins↗

PubMed2000

Molecular and physiological aspects of aflatoxin and sterigmatocystin biosynthesis by Aspergillus tamarii and A. ochraceoroseus.

Until recently, only three species (Aspergillus flavus, A. parasiticus and A. nomius) have been widely recognized as producers of aflatoxin. In this study we examine aflatoxin production by two other species, A. tamarii and A. ochraceoroseus, the latter of which also produces sterigmatocystin. Toxin-producing strains of A. tamarii and A. ochraceoroseus were examined morphologically, and toxin production was assayed on different media at different pH levels using thin layer chromatography and a densitometer. Genomic DNA of these two species was probed with known aflatoxin and sterigmatocystin biosynthesis genes from A. flavus, A. parasiticus and A. nidulans. Under the high stringency conditions, A. tamarii DNA hybridized to all four of the A. flavus and A. parasiticus gene probes, indicating strong similarities in the biosynthetic pathway genes of these three species. The A. ochraceoroseus DNA hybridized weakly to the A. flavus and A. parasiticus verB gene probe, and to two of the three A. nidulans probes. These data indicate that, at the DNA level, the aflatoxin and sterigmatocystin biosynthetic pathway genes for A. ochraceoroseus are somewhat different from known pathway genes.

Aflatoxins↗

PubMed2006

Mycotoxins in Australia: biocontrol of aflatoxin in peanuts.

The major mycotoxin problem in Australia is the formation of aflatoxins in peanuts by Aspergillus flavus and A. parasiticus. This is controlled by good farm management practice, segregation into grades on aflatoxin content at intake to shelling facilities, colour sorting and aflatoxin assays. A second problem is the potential presence of ochratoxin A in grapes and grape products, resulting from infection by Aspergillus carbonarius. Good quality control before and during wine making ensures ochratoxin A is kept to very low levels, but in dried vine fruit, ochratoxin A levels may be higher. Biocontrol by competitive exclusion has been developed as the most promising means of controlling aflatoxins in peanuts. Some details of the process are given, including some basic laboratory experiments.

Aflatoxins↗

PubMed2006

Mycobiota in poultry feeds and natural occurrence of aflatoxins, fumonisins and zearalenone in the Rio de Janeiro State, Brazil.

The intake of mycotoxin-contaminated feeds can lead to nutrient losses and may have adverse effects on animal health and on productivity. The aims of this study were (1) to determine the mycobiota present in poultry feed samples, and (2) to evaluate the natural occurrence of aflatoxin B(1), fumonisin B(1) and zearalenone. Fungal counts were similar between all culture media tested (10(3 )CFU g(-1)). The most frequent genus isolated was Penicillium spp. (41.26%) followed by Aspergillus spp. (33.33%) and Fusarium spp. (20.63%). High precision liquid chromatography was applied to quantify aflatoxin B(1) and fumonisin B(1). Thin layer chromatography was used to determine zearalenone levels. Aflatoxin B(1 )values ranged between 1.2 and 17.5 microg kg(-1). Fumonisin B(1) levels ranged between 1.5 and 5.5 microg g(-1). Zearalenone levels ranged between 0.1 and 7 microg g(-1). The present study shows the simultaneous occurrence of two carcinogenic mycotoxins, aflatoxin B(1) and fumonisin B(1), together with another Fusarium mycotoxin (zearalenone) in feed intended for poultry consumption. Many samples contained AFB(1 )levels near the permissible maximum and it could affect young animals. A synergistic toxic response is possible in animals under simultaneous exposure.

Aflatoxin B1↗