Description
The biosurfactants, tension active compounds produced by
microorganisms, have been successfully used in bioremediation processes and soil washing since the efficiency of these biomolecules in increasing the dispersion and the biodegradation of hydrocarbons. Their properties such as low toxicity and biodegradability are also very attractive for environmental applications. Thus, this study investigated potential application of two biosurfactants for enhanced removal capability and biodegradation of motor oil contaminated sand under laboratory conditions. The biosurfactants were produced by the yeast Candida sphaerica and by the bacterium Bacillus sp. cultivated in low-cost substrates. The ability of removing motor oil from soil by
the two biosurfactants was identified and compared with that of the synthetic surfactants Tween 80 and Triton X-100. Both crude and isolated biosurfactants showed excellent effectiveness on motor oil removal from contaminated sand under kinetic conditions (70-90%), while the synthetic surfactants removed between 55 and 80% of the oil under the same conditions. The increase in biosurfactants and synthetic surfactants concentration did not enhance the removal of oil. A contact time of 5-10 min under agitation seemed to be enough
for oil removal with the biosurfactants and synthetic surfactants tested. The crude and the isolated biosurfactant produced by C. sphaerica were able to remove high percentages of motor oil from packeded comumns (around 90%) when compared to the biosurfactant from Bacillus sp. (40%). For the degradation experiments conducted in motor oil contaminated sand enriched with sugar cane molasses, however, oil degradation was approximately 100% after 90 days in the presence of B. sp. cells, while the percentage of oil degradation did not exceed 50 % in the presence of C. sphaerica. The presence
of the biosurfactants increased the degradation rate in 10-20%, especially during the first 45 days of the experiments, indicating that biosurfactants acted as efficient enhancers for hydrocarbon biodegradation. The results indicated the biosurfactants enhancing capability on both removal and rate of motor oil biodegradation in soil systems.
