Statistical Optimization of Phenol Degradation by Bacillus pumilus OS1 Using Plackett–Burman Design and Response Surface Methodology

Abstract

Parameters such as initial phenol concentration, pH, temperature, inoculum size, and concentration of various medium components largely affect the phenol degradation ability of microbes; hence, these parameters must be optimized in order to achieve maximum phenol degradation. The present study is an attempt to optimize phenol degradation by Bacillus pumilus OS1, isolated from soil of crude oil spillage site. Experimental design methodology has been adopted for the optimization study. The Plackett–Burman design has determined five significant factors [pH, temperature, phenol concentration, inoculum size, and (NH4)2SO4 concentration] out of the nine variables, important for phenol degradation. Response surface analysis using central composite design has been used to study mutual interactions between these variables and to find their optimum levels. The predicted result shows that maximum phenol degradation (99.99 %) could be achieved at pH 7.07, temperature 29.3 °C, phenol 227.4 mg/l, inoculum size 6.3 % (v/v), (NH4)2SO4 392.1 mg/l. The correlation coefficient (R 2 = 0.9679) indicates an excellent agreement between the experimental values and predicted ones. A fairly good agreement between the model predicted value and the one obtained from subsequent experimentation at the optimized conditions confirms the validity of the model.