Abstract

In this study, an aerobic bacterial strain capable of utilizing di-n-butyl phthalate (DBP) as sole carbon source and energy was isolated from activated sludge collected from a plastic molding plant. Based on its morphology, physiochemical characteristics, and 16S rDNA sequence, the strain was identified as Serratia marcescens C9. The Taguchi method was used for determining the optimum condition of DBP degradation from aqueous solution by S. marcescens C9. An orthogonal array experimental design L₉ (3³) was chosen to employ the experiment and L₉ (3³) is consisted of three control factors (Temperature, pH and initial DBP concentration) and each factor has three different levels. DBP degradation rate was investigated as the quality characteristic to be optimized. In order to determine the optimum levels of the control factors precisely, range analysis and analysis of variance were performed. The optimum condition for DBP degradation was found to be temperature =37°C, pH= 7, C₀= 50 mg/l. In addition, first-order kinetic model was used to evaluate the degradation process of DBP at different initial concentrations in liquid medium. The results showed that the degradation half-life was about 1.35 d when the concentration of DBP was lower than 100 mg/l. This work suggested that the isolated strain C9 may have potential for use in bioremediation of DBP contaminated water.

Key words: Degradation, Taguchi method, first-order kinetic model, di-n-butyl phthalate,Serratia marcescens.