Phenol and trichloroethylene degradation by Pseudomonas cepacia G4: Kinetics and interactions between substrates

Abstract

Intact cells of Pseudomonas cepacia G4 completely degraded trichloroethylene (TCE) following growth with phenol. Degradation kinetics were determined for both phenol, used to induce requisite enzymes, and TCE, the target substrate. Apparent K(s) and V(max) values for degradation of phenol by cells were 8.5 μM and 466 nmol/min per mg of protein, respectively. At phenol concentrations greater than 50 μM, phenol degradation was inhibited, yielding an apparent second-order inhibitory value, K(SI), of 0.45 mM as modeled by the Haldane expression. A partition coefficient for TCE was determined to be 0.40 ± 0.02, [TCE(air)]/[TCE(water)], consistent with Henry's law. To eliminate experimental problems associated with TCE volatility and partitioning, a no-headspace bottle assay was developed, allowing for direct and accurate determinations of aqueous TCE concentration. By this assay procedure, apparent K(s) and V(max) values determined for TCE degradation by intact cells were 3 μM and 8 nmol/min per mg of protein, respectively. Following a transient lag period, P. cepacia G4 graded TCE at concentrations of at least 300 μM with no apparent retardation in rate. Consistent with K(s) values determined for degradation, TCE significantly inhibited phenol degradation.