Influence of phenol on biodegradation of p-nitrophenol by freely suspendedand immobilized Nocardioides sp NSP41

The effect of the presence of an alternate toxic compound (phenol) on the p -nitrophenol (PNP)-degrading activity of freely suspended and calcium algin ate immobilized Nocardioides sp. NSP41 was investigated. In the single subs trate experiments, when the concentration of phenol and PNP was increased t o 1400 mg l(-1) and 400 mg l(-1), respectively, the initial cell concentrat ions in the freely suspended cell culture should be higher than 1.5 g dry c ell weight l(-1) for complete degradation. In the simultaneous degradation experiment, when the initial concentration of phenol was increased from 100 to 400 mg l(-1), the specific PNP degradation rate at the concentration of 200 mg l(-1) was decreased from 0.028 to 0.021 h(-1). A freely suspended c ell culture with a high initial cell concentration resulted in a high volum etric degradation rate, suggesting the potential use of immobilized cells f or simultaneous degradation. In the immobilized cell cultures, although sim ultaneous degradation of PNP and phenol was maintained, the specific PNP an d phenol degradation rate decreased. However, a high volumetric PNP and phe nol degradation rate could be achieved by immobilization because of the hig h cell concentration. Furthermore, when the immobilized cells were reused i n the simultaneous degradation of PNP and phenol, they did not lose their P NP- and phenol-degrading activity for 12 times in semi-continuous cultures. Taken together, the use of immobilized Nocardioides sp. NSP41 for the simu ltaneous degradation of PNP and phenol at high concentrations is quite feas ible because of the high volumetric PNP and phenol degradation rate and the reusability of immobilized cells.