Research Product

For bioremediation of chlorinated aliphatic compounds to succeed, microorganisms must be identified that are capable of metabolizing these compounds. Twenty years ago, most chlorinated compounds were considered to be nonbiodegradable. Recently, many microbial successes in metabolizing chlorinated compounds have been uncovered. Four general enzymatic mechanisms are enlisted to cleave carbon-chloride bonds of organohalides (Wackett et al., 1992)and these mechanisms can serve to funnel the carbon atoms into central metabolic pathways. The biological mechanism(s) operative with a specific chlorinated compound is predicated on the chemical reactivity of the substance and the ability of evolutionary forces to produce enzyme catalysts capable of exploiting that unique reactivity. An understanding of the mechanisms involved in organohalide metabolism is directly relevant to the design of bioremediation systems. For example, one of the first design decisions is to choose between aerobic or anaerobic biotreatment systems. This decision is dependent on the chlorinated compound(s) to be treated. A partially chlorinated alkene would likely be treated best aerobically, while perchlorinated alkanes and alkenes would be treated anaerobically. If the chlorinated compound to be degraded is not a carbon and energy source for the metabolizing organism, alternatie growth-sustaining compounds must be present at the site or supplemented as part of the bioremediation protocol. Chlorinated aliphatic compounds can be toxic to bacteria, either by their solvent effect, which disrupts biological membranes, or by metabolic activation that generates toxic intermediates which react with cellular macromolecules, or by both effects. A knowledge of the organism(s) and the reaction mechanisms involved in halocarbon metabolism is crucial to maximize the bioremediation potential of any system.