Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Botany and Microbiology

Spoiled food products and beverages were screened for biosurfactant-producing bacteria. One hundred and ten bacterial isolates have been successfully isolated and purified from twenty samples. The biosurfactant production ability of all the bacterial isolates was investigated by five different methods including heamolytic activity, methylene blue agar plate method, emulsification index, oil spreading and drop collapse test. Based on screening assay, 39 isolates were selected for their ability to produce biosurfactants. Further morphological, physicochemical, and 16S rRNA gene sequence analysis of the most promising isolates revealed that they are belonging to the genus bacillus, staphylococcus and Pseudomonas. The isolate Pseudomonas aeruginosa MS1 was found to be a potential strain for biosurfactant production. Initial fermentation studies using mineral salt medium supplemented with corn oil resulted in a maximum reduction of surface tension to 28.8 mN/m after 48 hours, the highest emulsification index 56% after 72 hours and maximum biosurfactant yield 285 mg/l after 96 hours. Characterization studies were done using thin layer chromatography (TLC), Fourier transform infrared spectroscopy (FTIR) and Nuclear magnetic resonance spectroscopy (NMR). TLC was visualized with molisch{u00B4} reagent to detect the presence of rhamnose sugar and two spots were observed with Rf value 0.79, 0.3 belonging to mono-rhamnolipid and di-rhamnolipid molecules respectively

Issued also as CD