Optimizing the medium components in bioemulsifiers production byCandida lipolyticawith response surface method

Abstract

A response surface methodology was used to study bioemulsifier production by Candida lipolytica. A 24full experimental design was previously carried out to investigate the effects and interactions of the concentrations of corn oil, urea, ammonium sulfate, and potassium dihydrogen orthophosphate on the emulsification activity (EA) of the bioemulsifier produced by C. lipolytica. The best EA value (3.727 units of emulsification activity (UEA)) was obtained with a medium composed of 0.4 g of urea, 1.1 g of ammonium sulfate, 2.04 g of potassium dihydrogen orthophosphate, 5 mL of corn oil, 50 mL of distilled water, and 50 mL of seawater. A curvature check was performed and revealed a lack of fit of the linear approximation. The proximity of the optimum point was evident, as was the need for quadratic model and second-order designs that incorporate the effect of the curvature. Medium constituents were then optimized for the EA using a three-factor central composite design and response surface methodology. The second-order model showed statistical significance and predictive ability. It was found that the maximum EA produced was 4.415 UEA, and the optimum levels of urea, ammonium sulfate, and potassium dihydrogen orthophosphate were, respectively, 0.544% (m/v), 2.131% (m/v), and 2.628% (m/v).Key words: emulsification activity, factorial design, central composite design, optimization, biosurfactant.