Degradation Kinetics of Trichloroethylene by Methylosinus trichosporium PP358

Abstract

Degradation kinetics of trichloroethylene(TCE) by the resting-cell of the mathanotroph Methylosinus trichosporium PP358 was studied. When 20 mM formate was present in the reaction mixture as a reducing agent, the rate of TCE degradation followed the Michaelis-Menten kinetics and the maximum specific degradation rate(Vmax) and saturation constant (Km) were 14.0 nmol/min·mg cell and 124 μM, respectively. Methane and methanol inhibited the TCE degradation in a competitive mode and their inhibition constants(Ki) were estimated to be 107 μM and 3.4 mM, respectively. In the absence of formate, methane and methanol showed a more complex effect on the TCE degradation. At low concentrations, both substrates stimulated the degradation, while at high concentrations, they inhibited the degradation. The maximum specific degradation rate with methane or methanol was about 60 % or 80 % of the maximum specific degradation rate obtainable with added formate. Kinetic equations describing the complex effect of methane or methanol were proposed and the relevant kinetic constants were determined.