A total of 125 fungal isolates belonging to 47 species of Aspergillus, Penicillium, Alternaria, Fusarium and Trichoderma were screened for phytase-producing ability. Aspergillus niger was the most active in terms of phytase production, and the isolates produced extracellular phytase. Aspergillus niger isolate AUMC 134 showed the highest phytase production, followed by isolates AUMC 19A, AUMC 48A and AUMC 8A. The optimum environment for phytase production of Aspergillus niger was pH at 5.0-5.5, temperature of 45-55°C and substrate concentration of 0.8-0.16 mM. The hydrolytic action of the phytases indicated sequential hydrolysis of phosphate esters of phytic acid. The tested fungal phytases exhibited relatively high thermal stability.

A total of 125 fungal isolates belonging to 47 species of Aspergillus, Penicillium, Alternaria, Fusarium and Trichoderma were screened for phytase-producing ability. Aspergillus niger was the most active in terms of phytase production, and the isolates produced extracellular phytase. Aspergillus niger isolate AUMC 134 showed the highest phytase production, followed by isolates AUMC 19A, AUMC 48A and AUMC 8A. The optimum environment for phytase production of Aspergillus niger was pH at 5.0-5.5, temperature of 45-55°C and substrate concentration of 0.8-0.16 mM. The hydrolytic action of the phytases indicated sequential hydrolysis of phosphate esters of phytic acid. The tested fungal phytases exhibited relatively high thermal stability.

A total of 125 fungal isolates belonging to 47 species of Aspergillus, Penicillium, Alternaria, Fusarium and Trichoderma were screened for phytase-producing ability. Aspergillus niger was the most active in terms of phytase production, and the isolates produced extracellular phytase. Aspergillus niger isolate AUMC 134 showed the highest phytase production, followed by isolates AUMC 19A, AUMC 48A and AUMC 8A. The optimum environment for phytase production of Aspergillus niger was pH at 5.0-5.5, temperature of 45-55°C and substrate concentration of 0.8-0.16 mM. The hydrolytic action of the phytases indicated sequential hydrolysis of phosphate esters of phytic acid. The tested fungal phytases exhibited relatively high thermal stability.

Cereals are frequently infested by mycotoxin-producing fungi such as Gibberella zeae. G. zeae produces sexual spores (ascospores, dispersed by wind) and asexual spores (macroconidia, dispersed by rain droplets) to infect host plants. The production of the mycotoxin deoxynivalenol (DON) and the germination of ascospores and macroconidia of G. zeae were studied at 20 °C in relation to relative humidity (RH). The DON contents of wheat heads and autoclaved rice grain samples, artificially inoculated with ascospore or macroconidia suspensions of equal spore density, were determined at 35 days after inoculation by high-performance liquid chromatography (HPLC). The average DON production 35 days after inoculation was much lower on rice (3.95±1.34 mg kg−1) than on wheat heads (302.30±57.46 mg kg−1). Macroconidia inoculi produced more DON than ascospore inoculi at relative humidities >90%, but less DON between 53% and 80% RH. At RH ≤53%, no significant differences in DON production were observed between macroconidia and ascospore inoculi. DON production increased with RH irrespective of spore type. Germination of ascospores and macroconidia was monitored during incubation above six constant humidity solutions ranging from 30% to 93% RH. Ascospores only required a RH ≥53%, whereas macroconidia required RH of ≥80% for germination. The different humidity requirements of the two spore types for germination are discussed as a potential reason for the differential DON production of ascospore and macroconidia inoculi in relation to humidity. The results indicate that DON contamination levels partly dependent upon the interaction of spore type and RH and may confer an ecological advantage to G. zeae over other Fusarium head blight pathogens.

The natural occurrence of aflatoxin B1 (AFB1) and sterigmatocystin (ST) has been surveyed in 30 samples of commerical green and roasted coffee. AFB, and ST were found in one out of ten green coffee samples at levels of 25 and 64 ug/kg, respectively. No toxin was found in 20 samples of light and dark roasted coffee. The effect of caffeine on the growth and toxigenic potential of A. parasiticus and A. nidulans was examined in normal and decaffeinated coffee, as well as, in YES medium supplemented with different caffeine concentrations. Caffeine exhibit minor or no effect on fungal growth, but totally prevented the formation of AFB1 and ST in normal coffee. Decaffeinated green coffee induced the production of AFB1 and ST, but this stimulatory effect was decreased with roasted samples. Production of AFB1 and ST in caffeinated YES medium was depend on caffeine concentration and incubation time. AFB1 commenced to arise in small quantity after 21 days of incubation in the presence of 0.6% caffeine. Meanwhile, ST production decreased and delayed up to 14 days of incubation at 0.3% caffeine And completely inhibited at 0.6% caffeine. Data of this study help explain why coffee and other caffeine- containing commodities are poor substrates for mycotoxin production

The effects of fermentation and baking on the deoxynivalenol (DON) contamination level of rolls prepared with contaminated wheat flour were studied. Contaminated wheat was obtained from a field experiment where wheat heads were inoculated at anthesis using a Fusarium graminearum macroconidial suspension. The DON contamination level of dough decreased linearly by 45 % within a fermentation (32°C, 75 % relative humidity) period of 90 min. The decrease of the DON content in the dough due to fermentation was not related to yeast, starch or gluten. The DON contents of flour/ water mixtures were decreased under fermentation conditions, whereas no effect was observed if fermentation was omitted. After the centrifugation of flour/water mixtures, the effect of fermentation was observed in the supernatant, but not in the sediment, suggesting that a yet unidentified water-soluble compound of the flour was responsible for the reduction during fermentation. The DON content of rolls decreased almost linearly with baking time (0 - 20 min) but it was not significantly affected by baking temperature (220 vs. 250 °C). The DON content of the rolls decreased during baking at an average rate of 0.35 ′ 0.05 mg DON kg-1 dry mass min-1. Fermentation and baking decreased the DON content of the rolls to a similar extent, but a combination of both processes (fermentation with subsequent baking) did not result in a better reduction than one of the steps alone. The latter result suggests that the compound(s) responsible for the decrease of the DON content during fermentation is/are not heat stable. The DON contents of crust, dough and whole rolls did not differ significantly and the distribution of the DON within the rolls was not affected by yeast.

Soaking and boiling whole wheat kernels in water are the key steps in the preparation of an Egyptian dish called 'balila'. The effects of washing, soaking and boiling wheat kernels in tap water or in 0.1 M Na2CO3 solution on the deoxynivalenol (DON) content of the wheat kernels were studied. Boiling contaminated wheat kernels in water reduced the DON content of the grain by 70%. The mechanism of decontamination due to boiling is probably a leaching of DON out of the grain into the boiling medium. A combined treatment of soaking in 0.1 M Na2CO3 solution (pH 11) with subsequent boiling reduced the DON content of the grain by 93%. Data suggest that apart from leaching DON out of the kernels into the boiling medium, a degradation of DON occurred in alkaline medium. Modifying the traditional process of 'balila' preparation by using Na2CO3 solution may be useful to reduce the risk of mycotoxin exposure via 'balila'