Background:
This study investigated the 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.
Results:
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. 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 from
C. sphaerica were
able to remove high percentages of motor oil from packed columns (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 reached almost 100% after 90 d in the
presence of
Bacillus 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 d, indicating that biosurfactants acted as efficient enhancers for hydrocarbon biodegradation.
Conclusions:
The results indicated the biosurfactants enhancing capability on both removal and rate of motor oil
biodegradation in soil systems.
