Biotransformation of 1,1,1-trichloroethane, trichloromethane, and tetrachloromethane by a Clostridium sp

Abstract

A gram-positive, strictly anaerobic, motile, endospore-forming rod, tentatively identified as a proteolytic Clostridium sp., was isolated from the effluent of an anaerobic suspended-growth bioreactor. The organism was able to biotransform 1,1,1-trichloroethane, trichloromethane, and tetrachloromethane. 1,1,1-Trichloroethane was completely transformed (.99.5%) by reductive dehalogenation to 1,1-dichloroethane (30 to 40%) and, presumably by other mechanisms, to acetic acid (7%) and unidentified products. The reductive dehalogenation of tetrachloromethane led to the intermediate trichloromethane, which was further transformed to dichloromethane (8%) and unidentified products. The biotransformation occurred during the exponential growth phase, as well as during the stationary phase. Tetrachlorethene, trichloroethene, 1,1-dichloroethene, chloroethane, 1,1-dichloroethane, and dichloromethane were not biotransformed significantly by the organism.

Physiological meaning and potential for application of reductive dechlorination by anaerobic bacteria

“…The production of carbon dioxide from tetrachloromethane [16,17] and acetate from 1,1,1-trichloroethane [28] are overall substitutive reac-300 tions and seem to be exceptions to the rule that anaerobic bacteria transform halogenated compounds predominantly via reduction reactions. However, these transformations could involve a two-electron reduction to a carbenoid which would be hydrolysed to form carbon monoxide and acetaldehyde [29].…”

A Pseudomonas stutzeri gene cluster encoding the biosynthesis of the CCl4‐dechlorination agent pyridine‐2,6‐bis(thiocarboxylic acid)

“…Biological destruction of CCl 4 has been studied to identify transformation activities that may offer economical and effective remediation of this problem. CCl 4 dehalogenation activity has been identified among strictly anaerobic and facultative bacteria (Egli et al, 1987;1988;Galli and McCarty, 1989;Criddle et al, 1990;Mikesell and Boyd, 1990;Picardal et al, 1995). Our initial efforts were directed towards denitrification-linked CCl 4 dechlorination, not only because of the versatility of facultative bacteria but also because this was part of a larger effort aimed at remediation of a nitrate and CCl 4 contamination plume (Illman, 1993).…”

Enhanced Anaerobic Biotransformation of Carbon Tetrachloride in the Presence of Reduced Iron Oxides

“…Bacterial reductive dehalogenation has been studied extensively and can result from either microbial utilization of the chloroorganic compounds as terminal electron acceptors, or cometabolic transformation by microbial enzymes or cofactors [4]. Reductive dechlorination of CT has been demonstrated for a number of facultative or strict anaerobic bacteria [5][6][7][8], and evidence suggests a cometabolic mechanism involving * To whom correspondance may be addressed (picardal@indiana.edu).…”