BIODEGRADATION OF RECALCITRANT CHLOROPHENOLS BY COMETABOLISM

Under normal conditions in the environment a significant proportion of xenobiotic biodegradation involves cometabolism. Using the cometabolic principle, a procedure was developed to achieve accelerated biodegradation of persistent chemicals. Three stable chlorophenols [3,5-dichlorophenol (DCP), 3,4,5-trichlorophenol (TCP), and 2,3,5,6-tetrachlorophenol (TRCP)], which showed a total resistance to the biodegradation potential of a pentachlorophenol-degrading bacterial culture, were found to be biodegradable using the cometabolic technique. When a low-chlorinated monochlorophenol (3-MCP) was the cometabolite, only the medium-low chlorinated 3,5-DCP was biodegraded, while the medium chlorinated 3,4,5-TCP and the medium-high chlorinated 2,3,5,6-TRCP were not degraded by the culture. However, all three stable chlorophenols could be rapidly biodegraded when a highly chlorinated pentachlorophenol (PCP) cometabolite was used. If dual cometabolites (3-MCP and PCP) were used, all three stable chlorophenols were biodegraded, but at much slower rate. Maximizing biodegradation by use of the cometabolic technique to achieve accelerated biodegradation of stable chemicals is discussed.