Abstract
Accidents in petroleum platforms happen because of the absence of an effective fluid control inside the pipes, as occurred in 2010, when the scientists were not prepared to treat the oil spill in the Deepwater Horizon platform. In such environmental accident, non-biodegradable chemical dispersants were applied. As a safe alternative for the environment, the combination of the biotechnological potential of the microorganisms and the low cost waste materials results in the production of biosurfactants, known as the petroleum bioremediators. Thus, the optimization of operational parameters for biosurfactant production by Candida guilliermondii UCP 0992 grown in a low-cost medium and formulated with 4.0 % of corn steep, 2.5 % of molasses and 2.5 % of soybean residual oil was carried out in a 1.2 L bioreactor using response-surface methodology. The application of a Rotate Central Composed Design (RCCD) led to the identification of agitation speed, aeration, time and inoculum size as significant variables affecting the fermentation process. The optimal levels of the aforementioned variables were 250 rpm agitation speed, 132 h of cultivation time, 0.5 L/min of filtrated air and 4 % inoculum size. The experimental verifications allowed a maximum relative surface tension reduction to 31.45 mN/m and interface tension reduction to 9.04 mN/m, which was found to be equivalent to about 30.2 g/L isolated biosurfactant as estimated gravimetrically, thereby resulting in an improved production. Besides the optimization of operational parameters, the economic cost of € 22.37 was estimated to the biosurfactant produced according to the local price of the kWh. This work, therefore, showed that the fermentation time spent in flasks (144 h), could be reduced in 12 hours, increasing 3.6 times the yield and keeping the surface and interface tensions at the lowest level. Moreover, the biosurfactant produced by C. guilliermondii shows potential to be applied in oil spills.
