Degradation of Epichlorohydrin and Halohydrins by Bacterial Cultures Isolated from Freshwater Sediment

Abstract

Three bacterial cultures, the Gram-negative strain AD1 and the Gram-positive strains AD2 and AD3, were isolated from freshwater sediment after enrichment with epichlorohydrin as sole carbon source. In batch cultures of strain AD1 and strain AD3, epichlorohydrin was rapidly degraded to 3-chloro-1,2-propanediol. Crude extracts of strain AD 1 contained epoxide hydrolase activity towards epichlorohydrin, epibromohydrin, glycidol and propylene oxide as substrates. In contrast, strain AD2 did not actively convert epichlorohydrin but utilized 3-chloro-1,2-propanediol produced by slow chemical hydrolysis. No epichlorohydrin epoxide hydrolase was found in extracts of this organism. Crude extracts of strains AD1 and AD2 dehalogenated a number of mono-and dihalogenated alcohols and ketones, such as 1,3-dichloro-2-propanol, 3-chloro-1,2-propanediol, 1 -chloro-2-propanol, 1,3-dibromo-2-propanol, chloroacetone and 1,3-dichloroacetone. Dehalogenation yielded epoxides as products. The results suggest that epichlorohydrin is converted by strain AD1 via 3-chloro-l,2-propanediol and glycidol by the action of an epoxide hydrolase and a dehalogenase, respectively. The same route for dehalogenation proceeds in strain AD2, which, however, is dependent on chemical hydrolysis of epichlorohydrin rather than enzymic conversion.

Cloning of Two Halohydrin Hydrogen–Halide–Lyase Genes ofCorynebacteriumsp. Strain N-1074 and Structural Comparison of the Genes and Gene Products

“…3) Similar enzyme activities have been found in Flavobacterium, 29) Pseudomonas, 26) and Arthrobacter. 26 ) Recently, Janssen and co-workers have purified and characterized an enzyme from Arthrobacter sp. strain AD2, and named haloalcohol dehalogenase.…”

“…Epoxide hydrolase activities have also been detected in several bacteria,24 26) but little information about the biochemical and genetical characteristics of prokaryotic epoxide hydro lases is available. Recently, Jacobs et al 27) purified the opoxide hydrolase from Pseudomonas sp., and found the amino acid sequence of the amino termini of the intact protein and cyanogen bromide-generated peptides.…”

Halohydrin Dehalogenases Are Structurally and Mechanistically Related to Short-Chain Dehydrogenases/Reductases

“…Hydrolytic dehalogenases have been studied extensively, which has resulted in detailed insight into the structure and mechanism of several enzymes of this class (8,33). For other dehalogenases, structural and mechanistic data are hardly available.Halohydrin dehalogenases, also referred to as haloalcohol dehalogenases or halohydrin hydrogen-halide lyases, occur in the degradation pathways of halopropanols and 1,2-dibromoethane, where they catalyze the nucleophilic displacement of a halogen by a vicinal hydroxyl group in halohydrins, yielding an epoxide, a proton, and a halide ion (7,22,30,31). These enzymes also efficiently catalyze the reverse reaction, the halogenation of epoxides, and the dehalogenation of vicinal chlorocarbonyls to hydroxycarbonyls (2, 14, 31).…”

Investigation of Halohydrins Degradation by Whole Cells and Cell-free Extract of Pseudomonas putida DSM 437: A Kinetic Approach

“…In concert with a well characterized epoxide hydrolase, the haloalcohol dehalogenase constitutes an efficient degradation pathway of 1,3-DCP and epichlorohydrin into non-toxic metabolites. 3-CPD, which is considered the next intermediate of the pathway, is transformed to glycidol by haloalcohol dehalogenase, whereas glycerol is the final product 15,28 . Haloalcohol dehalogenases have broad substrate specificity and enantioselectivity towards aliphatic as well as aromatic vicinal haloalcohols 27 .…”