A. A. Zohri

Antibacterial, antidermatophytic and antitoxigenic activities of onion (Allium cepa L.) oil

The inhibitory effect of onion oil against the growth of various isolates of bacteria representing Gram-positive (4 isolates) and Gram-negative (4 isolates) species were studied. Results show that onion oil was highly active against all Gram-positive bacteria tested and only one isolate (Klebsiella pneumoniae) of Gram-negative bacteria. The inhibitory effect of onion oil against nine different species of dermatophytic fungi were also studied. Onion oil (200 ppm) completely inhibited the growth of Microsporum canis, M. gypseum and Trichophyton simii while the growth of both, Chrysosporium queenslandicum and Trichophyton mentagrophytes was completely inhibited by 500 ppm of onion oil. The growth of four other species of dermatophytic fungi was gradually reduced by increasing the concentrations of onion oil. The inhibitory effect of onion oil was also tested against four toxigenic isolates of fungi. Onion oil at different concentrations (100, 200 and 500 ppm) tested gradually reduced fungal growth and aflatoxin production by Aspergillus flavus IMI 89,717 and A. parasiticus var. globosus IMI 120,920. Fungal growth and production of sterigmatocystin and rubratoxin A by A. versicolor IMI 16,139 and Penicillium rubrum IMI 136,127 were completely inhibited by the addition of 200 ppm onion oil.

Progesterone side-chain degradation by some species ofAspergillus flavus group

Seventy isolates belonging to 6 species and one variety ofA. flavus group were shown to degrade the progesterone side-chain to yield Δ4-androstene-3, 17-dione and testosterone. The isolates of five species (A. flavo-furcatis, A flavus. A oryzae, A parasiticus andA. parasiticus andA. tamarii) possessed enzyme systems catalyzing the opening of ring D and formed testololactone as final steroid metabolite in addition to their ability to produce the above mentioned two products 11β-Hydroxy-Δ4-androstene-3, 17-dione was formed by onlyA. flavus andA. tamaru while 11β-hydroxytestosterone was produced byA. flavo-furcatis. A. parasiticus andA. subolivaceus. The chromatographic resolution of the mixture products obtained (when the selective isolate of each species reacted with 1 g of progesterone) revealed that 60–75% of progesterone was converted into Δ4-androstene-3, 17-dione (8–30%). testosterone (7–33%), testololactone (14–37%) and other products (3–40%). The most bioconversion activity was exhibited byA. oryzae, followed byA. parasiticus. The highest values of Δ4-androstene-3, 17-dione (30% of added progesterone) and testosterone (33%) were formed byA. flavus varcolumnaris while those of testololactone (37%) were produced byA. oryzae. A systematic variation could be observed between the different tested species ofA. flavus group with respect to the transformation reactions of progesterone. Comparative biotransformation results showed that essential differences exist between the tested species in this group; this biochemical differentiation may supplement the morphological and other physiological criteria used in the identification of the different species in theA. flavus group.

Filamentous fungi and mycotoxin detected in coconut

Fifty-nine species and one variety belonging to 25 genera of fungi were isolated from 25 coconut samples on glucose-Czapeks (25 genera and 55 species + 1 variety) and dichloran-glycerol (8 genera and 32 species + 1 variety) agar media at 28 degrees C. The common fungi on both media used were Aspergillus flavus, A. niger, Penicillium chrysogenum and Cladosporium cladosporioides. On glucose-Czapeks agar, A. flavus var. columnaris, P. oxalicum, Alternaria alternata, Rhizopus stolonifer and Trichoderma hamatum were recorded as common fungi while A. sydowii and Eurotium chevalieri were isolated with high frequency only on dichloranglycerol medium. Chromatographic analysis of the chloroform extracts of the coconut samples revealed that 5 out of 25 samples tested were naturally contaminated with aflatoxin B1 (15-25 micrograms/kg) and 3 samples contaminated with ochratoxin A (50-205 micrograms/kg).

Mycotoxin production on different cultivars and lines of broad bean (Vicia faba L.) seeds in Egypt

One hundred different cultivars and lines of broad bean (Vicia faba L.) seed samples were inoculated with Aspergillus flavus Link (CMI 102135) to determine varietal differences which may support or resist aflatoxin production. Thin-layer chromatographic analysis of the chloroform extracts of the different seed samples revealed that 11 cultivars/lines were highly resistant to seed invasion and aflatoxin production while 9 cultivars/lines showed partial resistance. The remaining 80 samples were susceptible to the establishment of A. flavus and aflatoxin accumulation. All the resistant cultivars/lines seed samples were inoculated also with three local isolates of fungi namely; Stachybotrys chartarum (Ehrenb. ex Link) Hughes, Aspergillus ochraceus Wilhelm, and Fusarium oxysporum Schlecht. The resistant seed samples were also resistant for colonization with these fungi and mycotoxin formation.

Progesterone transformation as a biochemical aid in classification of the genus Emericella.

A total of 65 isolates representing 13Emericella taxa (5 isolates of each of 12 species and 1 variety) had the ability to transform progesterone into 11α-hydroxyprogesterone. A systematic variation could be observed between the different testedEmericella taxa with respect to the transformation products. The isolates were divided according to the transformation types into six groups: (1) progesterone was hydroxylated into 6β-hydroxyprogesterone, 11α-hydroxyprogesterone and 6β, 11α-dihydroxyprogesterone— found inEmericella acristata andE. dentata; (2) E. aurantio-brunna andE. parvathecia hydroxylated progesterone into 11α-hydroxyprogesterone, 17α-hydroxyprogesterone and 11α,17α-dihydroxyprogesterone; (3)E. nidulans andE. quadrilineata formed the same three products as members of group (2) and form epicortisol; (4)E. nidulans var.lata, E. bicolor andE. variecolor transformed progesterone into a mixture of mono- di-and trihydroxy products; (5)E. striata andE. sublata exhibited an oxidative splitting of the progesterone side chain in position C-17 and hydroxylated progesterone into mono-and dihydroxy products; (6)E. rugulosa andE. unguis had the ability to degrade progesterone side-chain and to hydroxylate it into mono-, di- and trihydroxy products. This biochemical differentiation may supplement the morphological and other biochemical criteria used in the classification of theEmericella taxa.

Confirmation of the relationships of Aspergillus egyptiacus and Emericella nidulans using progesterone transformation

Isolates of Emericella nidulans (7 isolates), Aspergillus egyptiacus (7) and A. versicolor (5) were tested for their ability to transform progesterone. Consistent results were obtained between isolates of the same species. Whilst A. egyptiacus and E. nidulans possessed the enzyme system catalysing the transformation of progesterone into 11‐α‐hydroxyprogesterone, A. versicolor did not. Thus, progesterone transformation could be considered as further diagnostic evidence that A. egyptiacus is related to the Emericella group.

Progesterone transformations by three species ofHumicola

Five isolates belonging to three species of the genusHumicola were tested in this study for their ability to transform progesterone. An oxidative splitting of the side chain of progesterone with the formation of androst-4-ene-3,17-dione, testosterone and testololactone was achieved by all isolates tested ofH. fuscoatra andH. grisea. H. hyalothermophila transformed progesterone to 11α-, 11β-, 17α- and 21-hydroxyprogesterone and a dihydroxyl product (11α, 17α-dihydroxyprogesterone) with the addition of two trihydroxyl products,viz. cortisol and epicortisol. Qualitative and quantitative analysis of the different products obtained when a selective isolate of each species acted on progesterone were conducted. The chromatographic resolution of the mixture products obtained when the selective isolate of each ofH. fuscoatra andH. grisea had acted individually on 1 g progesterone revealed the presence of 25 and 20% unchanged progesterone, 20 and 22% androst-4-ene-3,17-dione, 25 and 23% testosterone and 30 and 35% testololactone, respectively. Seventy-four % of progesterone were bioconverted byH. hyalothermophila into 21-hydroxyprogesterone (6%), 17α-hydroxyprogesterone (5%), 11α-hydroxyprogesterone (11%), 11β-hydroxyprogesterone (12%), 11α,17α-dihydroxyprogesterone (5%), cortisol (21%) and epicortisol (13%). This is the first record of conversion of progesterone to both cortisol and epicortisol byH. hyalothermophila.

Effect of selenite and tellurite on the morphological growth and toxin production of Aspergillus parasiticus var. globosus IMI 120920

Aspergillus parasiticus var. globosus IMI 120920 was able to grow in presence of different concentrations tested (0.052–4.0%) of sodium selenite or concentrations up to 2.0% potassium tellurite. Growth of the fungus was decreased greatly by the increase of metals concentrations. Dark colour colony and black reverse were formed in presence of tellurite while reddish gray to grayish red colony colour and brownish red to orange red reverse were formed in presence of selenite. The fungal biomass was slightly decreased at lower concentrations and highly inhibited at higher concentrations of selenite or tellurite. Selenite slightly stimulated aflatoxin formation at lower concentrations and highly inhibited it at higher concentrations. Aflatoxin production was decreased greatly by increasing tellurite concentrations. Obvious malformations were observed in the morphological features of the fungus in presence of different levels of selenite or tellurite.

Aflatoxin formation and varietal difference of cow pea (Vigna unguiculata (L.) Walp.) and garden pea (Pisum sativum L.) cultivars.

Different cultivars of cow pea and garden pea seeds were surveyed for susceptibility or resistance towards the toxigenic and aflatoxin-producing mould (Aspergillus flavus IMI 102135). The results show that aflatoxin production varied among the different cultivars of both cow pea and garden pea. Morphological and histological characters of the different cultivars tested did not show any relation between colour, shape and size of seeds and the amount of aflatoxin produced.The chemical analysis of the different constituents obtained from both seed coats and seed kernels with susceptible, partially resistant and resistant cow pea and garden pea cultivars revealed that the resistant cultivars of cow pea (namely: Balady cultivar) and garden pea (namely: Melting Sugar cultivar) contained lower levels of sodium and higher levels of phosphate and potassium.

Based on biochemical and physiological behavior, where isAspergillus egyptiacus better placed?

Physiological and biochemical properties were tested in 45 isolates ofAspergillus egyptiacus (16 isolates),Emericella nidulans (16) andAspergillus versicolor (13). The three fungal species exhibited common and similar features. The big similarity betweenA. egyptiacus andE. nidulans was greater than betweenA. egyptiacus andA. versicolor. It included the inability to produce base either from sodium citrate or lactic acid media, growth at 45 °C (thermophilicity), and production of very similar pigmentations onAspergillus flavus andparasiticus agar.A. egyptiacus is therefore better placed in theAspergillus nidulans-Emericella assemblage.