Thesis (M.Sc.) - Cairo University - Faculty of Agriculture - Department of Microbiology

The present work was performed to investigate the isolation of biosurfactants producing bacteria, from hydrocarbon burned oilof 2 fuel stations at Giza governorate, having the ability to degrade one of fungicides,Topsin.Two segregates were distinguished as Bacillus cereus strain AM12605 and Serratia marcescenssp. marcescens ATCC13880 strain DSM 30121 by comparing its 16S rRNA sequence with those available in GATC Center in Germany.The strains were selected due to their capacities to create extracellular products (biosurfactants) able to reduce surface tension. To prove the potency of these isolates to produce biosurfactant, a screening method including emulsification was applied. The emulsification index E24 was 65% significance. Results demonstrated that the biosurfactant activity was steady at elevated temperature (25-40{u00B0}C) with wide domain of pH (5-8).To study the effect of these bacterial isolates on the growth of Zea mays in the presence of fungicide ,Topsin, data showed that the use of Bacillus cereus strain AM12605 with 0.5 g Topsin/l gave the best growth of Zea mays. While it was observed by 2.0g Topsin /l by using Serratiamarcescens ATCC 13880 strain DSM 30121 after 30 and 60 days from cultivation.With respect to the biodegradation of Topsin by abovementioned bacteria, results showed that the genus Bacillus (H2) was the most representative, with 99.74% removal after 3 days incubation while it was 99.68% after 5 days.So, under this study, these bacteria can apply for biodegradation of Topsin and use with some crops cultivation such as maize to increase the growth and eliminate some fungicides in soil

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