Aerobic biodegradation of 1,2-dichloroethane and 1,3-dichloropropene by bacteria isolated from a pulp mill wastewater effluent in South Africa

Large volumes of chlorinated aliphatic hydrocarbons are produced annually for a variety of industrial and commercial uses. They therefore constitute common contaminants of soil and groundwater causing serious environmental and human health problems. In this study, three bacteria were isolated from a pulp mill wastewater effluent in South Africa by culture enrichment technique and characterized for their ability to degrade 1,2-dichloroethane (1,2-DCE) and 1,3-dichloropropene (1,3-DCP). Specific growth rate constants of the organisms ranged between 0.864∼1.094 and 0.530∼0.585 d−1 in 1.2-DCE and 1,3-DCP, respectively, while the degradation rate constant of the compounds ranged variously between 0.33 and 1.006 d−1, with 1,2-DCE generally better utilized than 1,3-DCP. Gas chromatographic analysis revealed up to 75 and 80% removal of 1,2-DCE and 1,3-DCP, respectively, above that observed in the control bottles. These organisms also demonstrated high haloalkane dehalogenase activities with specific dehalogenase activities ranging between 0.25∼0.31 U (mg protein)−1. Analysis of their 16S rRNA gene sequences revealed that they belong to the generaPaenibacillus, Bacillus, andMicrobacterium.