Potential Removal of Styrene by the Aerobic Microorganism Rhodococcus erythropolis PTCC 1767

Biodegradation of styrene by an aerobic microorganism (namely, Rhodococcus erythropolis PTCC 1767) as well as the effects of bacterial cultures non-adapated and adapted to 90 mg/l styrene were investigated. In both cases, an initial biomass concentration of 0.31 mg/l and styrene concentrations of 10, 20, 30, 50, 70, 90, and 150 mg/ l were used and the tests were carried out at 32 °C and at pH 7. The results showed that the unadapted bacterial cultures were capable of biodegrading 10 mg/l in 15 h; however, removal efficiency was observed to decrease with increasing initial styrene concentration such that at a concentration of 150 mg/l, only 17% of the biomass was degraded over 48 h. On the other hand, the adapted microorganisms were capable of completly degrading Styrene at various initial concentrations of 10 to 150 mg/l over 2.7‒45 h. The kinetics of styrene biodegradation by R. erythropolis PTCC 1767 was also studied. The styrene bioremoval data fitted to the Monod model and to five inhibition kinetic models (namely, Haldane, Webb, Yano, Aiba, and Teissier-type). Among these models, the Haldene one was found to fit satisfactorily the kinetic data (R2>0.99, SSE=0.008) with the following Haldane model parameters: qm=4.235 mg/g dry cell h; Ks= 7.594 mg/l; and Ki= 34.58 mg/l.