Microbial Degradation of Chlorinated Unsaturated Fatty Acids
Incomplete degradation of multiple halogenated aromatic compounds [e.g., polychlorinated biphenyls (PCBs)] through the meta-fission pathway may be due to accumulation of halogenated unsaturated fatty acids. In order to study their further degradation, the enrichment culture technique was applied to isolate a microorganism capable of growing on the model compound chlorocrotonic acid (3-chlorobutenoic acid). The isolated strain, called CC1, grows on cis-chlorocrotonic acid, trans-chlorocrotonic acid, 3-chlorobutanoic acid, 2-chlorobutanoic acid, 2-chloropropionic acid, and chloracetic acid as sole sources of energy and carbon. Experiments with both resting cells and cell-free extract assays revealed that CC1 produces constitutively a 2-chloroalcanoic acid dehalogenase which acts on mono- and dichloroacetate, 2-chloropropionate, 2, 2-dichloropropionate, and 2-chlorobutanate. The specific activities in terms of chloride release that were measured with cell-free extracts were highest for 2-chloropropionate and 2-chloroacetate—ranging from 0.6 to 1.6 μMol/min/mg protein. Dehalogenase activity on β-chloro-C4 acids was not observed from cell-free extracts of cells grown on chlorinated or nonchlorinated acids, whereas it was observed from whole cells.