Optimization of Antibacterial Compounds Production by Aspergillus fumigatus Isolated from Sudanese Indigenous Soil

The purposes of the present study were to screen the ability of Aspergillus fumigatus to produce antibacterial compounds using different growth parameters namely, pH, temperature, agitation and time of fermentation and investigate the effect of the yield against bacterial isolates. A. fumigatus was isolated from arable lands in Sudan and identified macroscopically and microscopically. The pure fungal culture was inoculated in fermentation medium with different growth parameters. The fungal metabolites were extracted in intervals of 7, 8, and 9 days incubation period. No yield was observed at pH values of 6 and 8. A relatively high yield of active compounds was observed at pH 7, agitation speed of 75 rpm and 7 days contact time, while the highest yield was exhibited at
pH 7, agitation speed of 100 rpm and 8 days contact time. These metabolites were investigated for their inhibitory effects against indicator bacterial species. All indicator bacterial species showed resistance to 2.5% concentration of the crude extract. The 5% crude extract concentration exhibited small inhibitory effect (8 mm) against Salmonella typhimurium, moderate inhibitory effect (19 mm) against Listeria monocytogenes and high inhibitory effect (25 mm) against Pseudomonas aeruginosa. The pronounced inhibitory effect was observed with 10% concentration against Pseudomonas aeruginosa (40 mm) followed by Listeria monocytogenes (30 mm). A moderate inhibitory effect of the 10% crude extract was observed with Salmonella typhimurium (13 mm). The indicator bacteria Staphylococcus aureus showed resistance to all tested concentrations. The present study show that the growth parameters affect the yield but not the viability of Aspergillus fumigatus. The fungal metabolites have antibacterial effects.