الفهرس 
Marine environmentOnly 14 pages are availabe for public view
 |  | from | 236 |  |  |
| | | from | 236 | | |
Abstract
The potential of marine fungi to produce a vast array of secondary metabolites that are gaining importance for their biotechnological as well as medical and pharmaceutical applications has attracted our attention. However, the aim of this study to highlight the occurance of local marine fungal isolates having the chemical potential of producing bioactive metabolites with antimicrobial activity.
In our study, eighty eight marine- derived fungal isolate have been collected from different marine environments (Red Sea, Meditteranean Sea and Bitter Lakes) in Egypt and were tested for their antimicrobial activities against a panel of pathogenic microorganisms. The results showed that seventeen marine- derived fungal isolate were active against the tested bacterial pathogens only. Three marine- derived fungal isolates (No. 9, 10 and 16) were shown to be more active against most of the tested bacterial pathogens. Isolate No, 9 proved to be the most potent among them and for this reason, it was selected for further studies.
Upon traditional identification of the seventeen active marine-derived fungal isolate, it was shown that Aspergillus genus was the most dominant genus. Identification of the most potent marine-derived fungal isolate was confirmed by molecular tools and was identified as Aspergillus welwitschiae. Optimization of some factors affecting the antibacterial activity of Aspergillus welwitschiae revealed that A. welwitschiae gave maximum antibacterial activity when grown on Czapek- dox broth medium, pH 9 with agitation speed 150 rpm at incubation temperature of 25°C for three days of incubation period. A culture of A. welwitschiae was prepared with the optimized conditions and was subjected to extraction process by using different organic solvents. Results showed that ethyl acetate was the only effective solvent among other tested organic solvents in extracting antibacterial metabolites from A. welwitschiae. The crude organic extract was purified using thin layer chromatography technique and then was subjected to structural elucidation using different spectroscopic techniques as FTIR, MS and NMR. Results showed that the antibacterial activity of A. welwitschiae was by the action of two compounds an ester (bis-2-(ethylhexyl) phthalate) and acid Mono (2-ethylhexyl) phthalate. The separation of these two compounds from each other resulted in the loss of the antibacterial activity by A. welwitschiae, which reflected the synergistic pattern of the two compounds together Upon evaluating cytotoxic activity of the extracted antibacterial metabolites (ester and acid together) against WI- 38 cell line (human lung fibroblast normal cell); there was a very weak inhibitory activity against human fibroblast normal cells suggesting the possibility of considering these metabolites as a safe compound for further steps as a pharmaceutical product.