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 Ks and Vmax values for degradation of phenol by cells were 8.5 microM and 466 nmol/min per mg of protein, respectively. At phenol concentrations greater than 50 microM, phenol degradation was inhibited, yielding an apparent second-order inhibitory value, KSI, of 0.45 mM as modeled by the Haldane expression. A partition coefficient for TCE was determined to be 0.40 +/- 0.02, [TCEair]/[TCEwater], 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 Ks and Vmax values determined for TCE degradation by intact cells were 3 microM and 8 nmol/min per mg of protein, respectively. Following a transient lag period, P. cepacia G4 degraded TCE at concentrations of at least 300 microM with no apparent retardation in rate. Consistent with Ks values determined for degradation, TCE significantly inhibited phenol degradation.