TRANSFORMATION KINETICS OF CHLORINATED ETHENES BY METHYLOSINUS-TRICHOSPORIUM OB3B AND DETECTION OF UNSTABLE EPOXIDES BY ONLINE GAS-CHROMATOGRAPHY

A rapid and accurate method for the determination of transformation ki netics of volatile organic substrates was developed. Concentrations we re monitored by on-line gas chromatographic analysis of the headspace of well-mixed incubation mixtures. With this method, the kinetics of t ransformation of a number of C-1 and C-2 halogenated alkanes and alken es by Methylosinus trichosporium OB3b expressing particulate methane m onooxygenase or soluble methane monooxygenase (sMMO) were studied. App arent specific first-order rate constants for cells expressing sMMO de creased in the order of dichloromethane, vinyl chloride, cis-1,2-dichl oroethene, trans-1,2-dichloroethene, 1,1-dichloroethene, trichloroethe ne, chloroform, and 1,2-dichloroethane. During the degradation of tric hloroethene, cis-1,2-dichloroethene, trans-1,2-dichloroethene, and vin yl chloride, the formation of the corresponding epoxides was observed. The epoxide of vinyl chloride and the epoxide of trichloroethene, whi ch temporarily accumulated in the medium, were chemically degraded acc ording to first-order kinetics, with half-lives of 78 and 21 s, respec tively. Cells expressing sMMO actively degraded the epoxide of cis-1,2 -dichloroethene but not the epoxide of trans-1,2-dichloroethene. Metha ne and acetylene inhibited degradation of the epoxide of cis-1,2-dichl oroethene, indicating that sMMO was involved.