Optimization study for maximizing 2,4-dichlorophenol degradation by Kocuria rhizophila strain using response surface methodology and kinetic study

Abstract

In the present study, the combined effect of four experimental parameters i.e. pH, temperature (°C), inoculum size % (v/v) and ammonium sulphate concentration (g L−1) at different levels on biodegradation of 2,4-dichlorophenol (2,4-DCP) by newly isolated Kocuria rhizophila strain 11Y was investigated using the central composite design. The maximum of 98% degradation for 50 mg L−1 2,4-DCP was observed at an optimized condition, i.e. pH 7.45, temperature 36°C, inoculum size 10% (v/v) and (NH4)2SO4 concentration 1.6 g L−1 which is 15.2% higher than unoptimized condition. Also, the strain was able to utilize high concentration of 2,4-DCP up to 400 mg L−1 at an optimized condition which is much higher than at unoptimized condition and the degradation efficiency increased significantly. The biodegradation kinetic of 2,4-DCP at different initial concentrations shows that the degradation rate increases up to 350 mg L−1 and after that it started to decrease. The biodegradation kinetic parameters calculated for 2,4-DCP up to 400 mg L−1 were maximum rate of degradation (Rm) = 1.17 mg DCP h−1 L−1, half-saturation constant (Ks) = 568.1 mg L−1 and inhibition constant (Ki) = 215.63 mg L−1.