Three biosurfactants produced by bacterial isolates from polluted soil,
i.e. Bacillus subtilis, P. aeruginosa, and B. cereus were studied and compared
from diverse points of view. Among these bacteria, Bacillus subtilis
could be positioned well, by taking into account the overall biosurfactant
production rate, resistance and stability at extreme conditions and
influence on oil recovery. The biosurfactant produced by B. subtilis also
attained an emulsion index of 75% for crude oil. It showed good
surface activity with a decrease on surface tension of medium from 72
to 25 mN/m. The results of biosurfactant flooding experiment using
B. subtilis showed 25% oil recovery. This work was another demonstration
of usefulness of traditional screening and isolation of indigenous
microorganisms for industrial applications. Genetically engineered
microorganisms could also be used for production of biosurfactants
with special design in MEOR application. The ex situ production could
decrease the concerns related to the field applications of genetically
modified microorganisms and this could be the subject for future studies