Serratia marcescens P25, A New Strain Isolated From The Phycoplane of the Red Marine Alga Punctaria sp Produced Potent Biosurfactant Used for Enhancing the Bioremediation of Spent Motor Oil-Polluted Soil

Abstract

Samples of marine algae were collected from a coastal area at Abokir, Alexandria, and identified as: Punactraia sp (brown alga), Colpomenia sp (brown alga), Jania sp (red alga) and Ulva sp (green alga). 25 bacterial strains were isolated and purified from the phycoplane of Punctaria sp and were screened for the production of biosurfactants using cheap substrate (waste frying oil). The production of biosurfactants was tested by the plug agar and the ODA method. 60% and 80% of the tested strains were biosurfactant producers when the plug agar and the ODA method respectively used. Five red pigmented strains were very active biosurfactant producers (158-167.6 Cm 2 ODA) were selected and studied for their emulsification activity and their stability at wide range of temperature (0-121°C), pH values (2-12) and salinity (5-25% NaCl-W/V). The selected five bacterial strains were identified as members of Serratia marcescens. Strain P25 was characterized by producing a biosurfactant of more stability at wide range of temperature, pH and salinity, this is in addition to its ability to produce high emulsion activity against spent motor oil. The produced emulsion was stable at 7-30 days. The above characters give this Serratia marcescens P25 strain a potential application in petroleum industry such as cleaning oil storage tanks, recovery of oil from oily sludge, microbial enhanced oil recovery (MEOR),washing oilcontaminated soil and enhancing the bioremediation of hydrocarboncontaminated sites. The cell free culture broth (supernatant) containing the biosurfactant that was produced by strain P25 was sterilized and applied for the bioremediation of spent motor oilcontaminated soil. The result show that the addition of the sterilized supernatant alone increased the biodegradation of the oil to 65.0±5.2%. Addition of NP fertilizer alone failed to increase the biodegradation more than 46.0±2.0%, while in the presence of a mixture of biosurfactant and NP (BRNP) the biodegradation increased to 60.0±5.0%. Statistically, no significant difference between the result in presence of BR in the presence of BRNP (P>0.05). It can be concluded that the promising factor in the biodegradation of spent motor oil is the addition of BR alone or in combination with NP.