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 Cm2 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 oil- contaminated soil and
enhancing the bioremediation of hydrocarbon- contaminated 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 oil- contaminated 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.
