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 mothPrays 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.
Key words: Bacillus subtilis, biosurfactant, central composite design, optimization, Prays oleae.
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