Effect of pH on the toxicity and biodegradation of pentachlorophenol by Sphingomonas sp strain P5 in nutristat culture

Abstract

A polychlorinated‐phenol degrading bacterium, Sphingomonas sp. strain P5, was grown in nutristat culture (i.e., a continuous culture at a controlled substrate concentration) with pentachlorophenol (PCP) as the sole carbon and energy source. During steady state conditions, the effect of the medium pH on the growth of strain P5 on PCP was established. At lower pH values PCP exhibited a stronger toxicity than at higher pH values. Inhibition of the growth of strain P5 by PCP was correlated to the concentration of the undissociated phenol in the system, rather than to the dissociated or total PCP concentration. The results indicate that acidification of natural environments may enhance the toxicity of chlorophenols and suggest that treatments to increase environmental pH may reduce risk of chlorophenol toxicity at acidified sites.