Effects of surfactants and temperature on PCP biodegradation

The effects of temperature and surfactant concentration on the degradation of pentachlorophenol (PCP) by a pure culture of Sphingomonas chlorophenolicum sp. Strain RA2 were studied. An anionic, a cationic, and two nonionic surfactants were tested at concentrations above and below their critical micellar concentrations (CMC). Each surfactant was tested at four temperatures between 10 and 25 degrees C. PCP degradation curves were modeled based on Monod growth kinetics. Degradation curves were also fit using inhibition models accounting for the effects of temperature and surfactant concentration. No PCP degradation activity was observed in the presence of the cationic surfactant. The anionic surfactant had a more inhibitory effect at lower concentrations than the nonionic surfactants, which occurred at surfactant concentrations well below the CMC at all temperatures. Nonionic surfactants showed no inhibition at sub-CMC concentrations and higher temperatures. In general, the surfactants caused more inhibition at lower temperatures. The exception was a slight enhancement of PCP degradation at 10 degrees C for low concentrations of the nonionic surfactants.