a b s t r a c t
Surfactants are amphipathic molecules that accumulate at interfaces, decrease interfacial tensions, and
form aggregate structures such as micelles. Biosurfactants constitute one of the main classes of natural
surfactants produced by microorganisms, being classified in accordance with their chemical composition
or microbial origin. These polymers had attracted, in the last few years, considerable interest due to
biodegradable nature, low toxicity and diversity of applications. In this paper the biosurfactant from Candida
sphaerica UCP 0995 grown in distilled water supplemented with 9% ground-nut oil refinery residue
plus and 9% corn steep liquor was first produced in shake flasks and in a bioreactor. The biosurfactant
decreased the surface tension of water from 72 to 25 mN/m with a yield of 8.0 g/L when produced in
shake flasks while the biosurfactant produced in the bioreactor reduced the surface tension for 27 mN/m
with a yield of 21 g/L after 144 h. The biosurfactant was then tested for demulsification of motor oil emulsions,
showing values around 40%. The crude biosurfactant was capable of dispersing approximately 90%
of oil droplets in seawater and proved to be non-toxic to indigenous marine microbiota. The biosurfactant
acted as a solubilizer of motor oil in sea water as demonstrated by the acceleration and growth of
the indigenous microorganisms throughout the 30 days of cultivation. The present findings indicate the
application potential of the biosurfactant produced by C. sphaerica in the oil industry as a complement
to remediation processes involving contaminated water