Microbial degradation of PCBS by a two-stage process

There is considerable interest in the development of biological processes for PCB degradation. However, a consideration must be made for the effects of the accumulation of toxic intermediates on process design, and on release to the environment. Chlorobenzoates are the most noted intermediates of aerobic PCB degradation. Three hybrid bacterial strains have been constructed and shown to be able to utilise all of the monochlorobiphenyls as the sole source of carbon. Chloride was released in stoichiometric concentrations, suggesting that complete mineralisation had occurred. One of the strains, Pseudomonas cepacia JHR22, has been shown to be able to utilise 2, 3 and 4 mono-, and 2,4 and 3,5 dichlorobenzoate as carbon source. However, utilisation of chlorobiphenyls or chlorobenzoates was inhibited in the presence of 2,3 or 3,4 dichlorobenzoate. Preliminary data indicates that mixed cultures of the three hybrid strains are able to degrade most of the congeners present in Aroclor 1221, although the extent of mineralisation has not yet been established.