Statistical optimization of low-cost medium for economical production of Bacillus subtilis biosurfactant, a biocontrol agent for the olive moth Prays oleae

Abstract

Biosurfactants are currently not a feasible alternative to chemically synthesized surfactants as a result
of their potentially high production costs. In this work, Bacillus subtilis SPB1 biosurfactant was shown
to be efficient in the biocontrol of the olive moth Prays oleae. Its production was improved by
optimizing the medium components using inexpensive substrates. The effect of orange peels, soya
bean and diluted sea water on SPB1 biosurfactant production was studied and was adjusted using
central composite design. The experimental results were fitted to a second-order polynomial model that
yielded a determination coefficient of R2
=0.932. The optimal medium for biosurfactant production was
found to be composed only by orange peels (15.5 g/L), soya bean (10 g/L) and diluted sea water (30%).
The predicted and observed response were 4.3 g/L (with desirability = 0. 21) and 4.45 g/L, respectively.
In comparison to original level production, two fold increases had been obtained.