Cometabolism of pentachlorophenol by microbial species

Abstract

Pentachlorophenol (PCP) cometabolism in the presence of dextrose was investigated with a pure culture Pseudomonas cepacia and an acclimated mixed culture developed from a local activated sludge plant. The Ps. cepacia cells degraded PCP up to 50 mg/l without any significant lag, but at higher PCP concentrations (>50 mg/l and up to 100 mg/l) there was a significant lag period (up to 30 h) before the degradation started. Overall, PCP degradation was about 80% in these systems. PCP was found to be a non-competitive inhibitor of Ps. cepacia with an inhibition constant (Ki) of 222 mg/l. The Ps. cepacia cells were unable to use PCP as a sole carbon and energy source.The mixed culture cometabolized PCP in the presence of dextrose at rates somewhat similar to that of Ps. cepacia up to PCP concentrations of 100 mg/l. These cells, acclimated to PCP at a particular concentration, degraded PCP up to the acclimation concentration fairly rapidly, but at PCP concentrations higher than the acclimation concentration, the degradation rates were much slower. The mixed culture cells could be progressively acclimated to using up to 100 mg/l PCP as sole carbon and energy source with degradation rates similar to those when dextrose was present as a primary metabolite. The PCP and dextrose utilization by the mixed culture was characterized by a diauxic growth pattern.