Investigation of the Use of Terpenes as Cosubstrates in the Cometabolic Biodegradation of PCBs by Comomonas Testosteroni

Abstract

Polychlorinated biphenyls (PCBs) have caused concern because of their widespread distribution, relative recalcitrance to natural degradation, and their adverse health effects. PCBs are formed by a biphenyl nucleus carrying 1 to 10 chlorines. There are 209 possible PCB congeners that differ in number and position of chlorines on the biphenyl ring [1]. Commercial mixtures of PCB congeners include Aroclors (Monsanto, USA), and Kanechlors (Kanegafuchi, Japan), each of which typicaly contain from 60 to 80 congeners [2]. PCBs were used extensively in dielectric fluids, lubricants, plasticizers, solvents, and paints due to their physical and chemical stability, but were banned by the U.S. Environmental Protection Agency (EPA) in 1979 when the accumulated evidence suggested that PCBs were potent carcinogens. PCBs are highly hydrophobic with low water solubility, and they migrate through soil very slowly. Such properties limit the spread of PCBs but also limit the use of soil-washing to remediate PCB contaminated soils. Their low solubility also limits their bioavailability to microorganisms that could degrade them [3]. Remediation of PCB contaminated sites is a national priority, but current technologies are expensive and often lead to byproducts that are environmentally problematic. Bioremediation is emerging as a potentially inexpensive and efficacious technology, although PCB bioremediation only occurs in the presence of cosubstrates.