الفهرس 
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Abstract
SUMMARY
Mycotoxins are toxic secondary metabolites produced by toxigenic molds. Almost all toxigenic molds produce spores and are widely distributed in our environment. They can contaminated and produce mycotoxins in human food or animal feed during production, transport, processing and storage. Consumption of mycotoxins by humans or animals causes adverse health effects such as liver and kidney damage, cancer, and death.
In this investigation, a total of eighty molds were isolated from different food samples. Seven A.flavus isolates were found to be AFs producers. Isolate No.66 was found to give the highest amount of AFB1 1900µg/100ml, medium. So, it was selected to carry a series of experiments such as (environmental, nutritional requirements, detoxification effect of preservative salts, essential oils (Eos) and lactic acid bacteria (LAB) and aflR gene expression).
The reached results can be summarized as follow:
1- A total of 80 molds were isolated from cardamom, peanut 1, peanut 2, maize flour, corn flour, wheat flour1, and wheat flour2. These molds belonging to 7 genera include: Aspergillus , Alternaria , Cladosporium, Curvularia , Fusarium, Penicillium, Mucor, and Rhizopus.
2- All Aspergillus flavus isolates were screened for their ability to produce aflatoxins, 7 ones were able to produce AFs, but the isolate No. 66 was found to be the highest of them 1900µg/100ml, medium.
3- The highest level of aflatoxin produced in broth culture by A.flavus (No. 66) isolated from wheat flour was observed at 30ºC after 7 days 1960 µg/100ml medium, while low levels observed after 21 day at 15ºC and 45ºC, there were no growth and no aflatoxin production.
4- The initial pH of the medium is another important factor; the maximal toxin production was observed at pH 5.0 2000 µg/100ml medium, and was reduced at lower 2, 3, & 4or higher pH 6, 7, 8, 9,& 11 values.
5- The tested simple sugars such as glucose, fructose and sucrose were excellent carbon sources for both growth and aflatoxin production 2000, 1950, 2000 µg/100ml medium, respectively of the A.flavus. In contrast, more- complex sugars like lactose and mannitol did not support A. flavus aflatoxin production.
6- When yeast extract, casein were used as sole nitrogen sources, they supported toxin production more than peptone, beef extract, KNO3, NaNO3, and NH4Cl,which did not support both growth and aflatoxin production. However, yeast extract stimulated both growth and aflatoxin production 1.63g/100ml, 1960 µg/100ml medium, respectively of the experimental isolate.
7- Among the amino acids tested, L-lysine gave the highest aflatoxin production 1340 µg/100ml medium. On the other hand, L-methionine, L- asparagine and L- Aniline completely inhibited the production of aflatoxin.
8- Both sodium benzoate and potassium sorbate completely inhibited the growth and AFB1 productions of A. flavus isolate No.66. They have fungistatic and fungicide effects, respectively at pH 4.0.
9- Among the tested essential oils, anise oil had the inhibitoriest effect on the growth and AFB1 production at 150 µl/100ml medium with fungicide effect. As well as, caraway and fennel had the same effect at 150 µl/100ml medium but with fungistatic effect. While Nigella inhibited both growth and AFB1 production with fungicide action at concentration 2000 µl/100ml medium.
Three (LAB) strains, Lactobacillus rhamnosus , Lactobacillus bulgaricus, Streptococcus thermophilus were used as detoxification agents to prevent or reduce AFs production by A.flavus isolate No.66 at different temperature, pH , incubation period, media, and inoculation treatment.
10- When A.flavus co –cultivated with used LAB strains, there was high detoxification activity at 30, 37ºC, pH 4.0, 6.0 inculation period 3, 5,& 7 day, and (YES) medium.
11- When A.flavus co –cultivated with used LAB strains, there was no difference of detoxification activity with different inoculation treatments (after, before, and simultaneous).
12- There was no thermal stability for heated antifungal metabolites of LAB when used with both high temperatures 70, 121 ºC and incubation time prolongation.
13- All strains of LAB tested had the ability to bind AFB1; however, they varied in the rate of binding. Strep. thermophilus> Lb.rhamnosus > Lb. bulgaricus. There binding capacity was increased when bacterial pellets were treated with acid or heat.
14- By using quantitative real time- PCR to evaluate aflR gene expression, our result showed that detection of transcription level of aflR gene was not always correlated to the actual toxicity of samples.