Thesis (Ph.D.) - Cairo University - Faculty of Agriculture - Department of Microbiology

Due to the presence of many microbes has a high ability to produce biosurface tension reducer from inexpensive renewable substrates. Recently it was reported that biosurfactants have many properties and applications. This study aimed to isolate biosurfactant producer{u2019}s microbes with heavy metals tolerance using different screening methods from different districts in Egypt. Hundred and seventy-one isolates were isolated from 10 different soil samples in different regions in Egypt. Soil analysis was performed to check for soil nutrients, pH level, the percentage of organic matter, and the volumetric distribution of soil granules. The total microbial count has assessed, and the morphological characterization of microbial isolates has identified. The lipase activity, the Parafilm-M method, Oil spreading technique, and the Emulsification index (E24), were performed. Organic matter percentage of soil samples were ranged from 0.07 % to 0.35 %. The most soil types were respectively, silt clay soil and sandy soil while the pH level was found to be neutral to alkaline. Out of 171 isolates, 80 (46.78 %) isolates were showed a high ability to degrade the used oil completely, while 91 (53.22 %) isolates have a low ability to degrade the oil. Among those 80 isolates, only 21 isolates were categorized as strong isolates according to their results in oil degradation, ParafilmM-and oil spreading tests. Our study reveals the high ability of biosurfactant production among Egyptian isolates isolated from highly nutrient-rich soils from different regions in Egypt. High resistance to different heavy metals was also shown which makes our isolates a promising source for different applications

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