Cometabolism of cis-1,2-Dichloroethene by Aerobic Cultures Grown on Vinyl Chloride as the Primary Substrate

Abstract

An aerobic enrichment culture was grown on vinyl chloride (VC) as the sole source of carbon and energy. In the absence of VC, the enrichment culture cometabolized cis-1,2-dichloroethene (cDCE) and, to a lesser extent, trans1,2-dichloroethene (tDCE), beginning with oxidation to the corresponding DCE-epoxides. When provided with VC (1.3 mM) and cDCE (0.2-0.3 mM), the enrichment culture cometabolized repeated additions of cDCE for over 85 days. Cometabolism of repeated additions of tDCE was also demonstrated but at a lower ratio of nongrowth substrate to VC. VC-grown Pseudomonas aeruginosa MF1 (previously isolated from the enrichment culture) also readily cometabolizes cDCE, with an observed transformation capacity (Tc,obs) of 0.82 micromol of cDCE/mg of total suspended solids (TSS). When provided with VC and cDCE, MF1 did not begin cometabolizing cDCE until nearly all of the VC was consumed. The presence of cDCE reduces the maximum specific rate of VC utilization. A kinetic model was developed that describes these phenomena via Monod parameters for substrate and nongrowth substrate, plus inactivation and inhibition coefficients. MF1 did not show any cometabolic activity on tDCE or trichloroethene and very limited activity on 1,1-DCE (Tc,obs = 2 x 10(-5) micromol/mg TSS). Above 40 microM, tDCE and TCE noticeably increased the maximum specific rate of VC utilization, even though neither compound was consumed during or after VC consumption. High concentrations of 1,1-DCE (950 microM) completely inhibited VC biodegradation. As there is currently no evidence for aerobic biodegradation of cDCE as a sole source of carbon and energy, the results of this study provide a potential explanation for in situ disappearance of cDCE when the only other significant substrate available is VC. It is fortuitous that the VC-grown cultures tested exhibit their highest cometabolic activity toward cDCE, because it is the predominant DCE isomer formed during anaerobic reductive dechlorination of trichloroethene and tetrachloroethene.

Epoxyalkane:Coenzyme M Transferase in the Ethene and Vinyl Chloride Biodegradation Pathways of Mycobacterium Strain JS60

“…In addition, several ethene-assimilating strains have been evaluated as biocatalysts for the production of epoxides (17,46). Much research has focused on the kinetics of VC and ethene oxidation and on the cometabolism of related substrates (7,24,49), while fundamental questions concerning the catabolic pathways and enzymes involved have been somewhat neglected. The biochemical traits that distinguish bacteria that grow on both substrates from those that grow on ethene alone are unknown, as are most of the metabolic intermediates in both pathways.…”

Distribution of the Coenzyme M Pathway of Epoxide Metabolism among Ethene- and Vinyl Chloride-Degrading Mycobacterium Strains

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Aerobic bacteria that grow on ethene and vinyl chloride (VC) are widely distributed in the environment and have attracted interest because of their potential applications in bioremediation and biocatalysis (5,6,11,12,32,33). The first step in ethene and VC assimilation is known to be a monooxygenase reaction yielding epoxyethane from ethene (5, 7) and chlorooxirane from VC (12, 33), but the downstream pathways are not well understood.

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Characterization of Microbes Capable of Using Vinyl Chloride and Ethene as Sole Carbon and Energy Sources by Anaerobic Oxidation

“…Oxygen was consumed concurrently with VC. In both bottles, cDCE was also consumed, suggesting possible aerobic cometabolic activity with VC serving as the primary substrate (Verce et al, 2002). Over 345 days of incubation, VC declined by 19% in an autoclaved control bottle, demonstrating that the substantially higher consumption rate of VC in the live bottles was a biotic process.…”