Simultaneous degradation of p-nitrophenol and phenol by free and immobilized cells of nocardioides sp.

Abstract

A ρ-nitrophenol (PNP) mineralizing bacterium was isolated from industrial wastewater and identified as Nocardioides sp. strain PNP101. This strain could degrade PNP and phenol simultaneously by utilizing PNP as a sole nitrogen source. The addition of phenol enhanced the specific growth rate and specific PNP degradation rate by almost 100%. This seems to be due to the increased cell mass by utilizing different enzyme systems in the degradation of PNP and phenol. This also explains that in the case of low phenol concentration, 4-nitrocatechol was detected transiently after exhaustion of phenol and then disappeared concomitantly with nitrite release and PNP degradation. Calcium alginate immobilized cells enhanced the volumetric degradation rate of PNP and phenol compared to free cells. In semi-continuous cultures, the immobilized cells could mineralize up to 2.5 mM of PNP and phenol, and could be reused 16 times without losing the simultaneous degradation activity.