AEROBIC MINERALIZATION OF CHLOROBENZOATES BY A NATURAL POLYCHLORINATED BIPHENYL-DEGRADING MIXED BACTERIAL CULTURE

A natural mixed aerobic bacterial culture, designated MIXE1, was found to be capable of degrading several low-chlorinated biphenyls when 4-c hlorobiphenyl was used as a co-substrate. MIXE1 was capable of using a ll the three monochlorobenzoate (CBA) isomers tested as well as 2,5-, 3,4- and 3,5-dichlorobenzoate (dCBA) as the sole carbon and energy sou rce. During MIXE1 growth on these substrates, a nearly stoichiometric amount of chloride was released: 0.5 g/l of each chlorobenzoate was co mpletely mineralized by MIXE1 after 2 or 3 days of culture incubation. Two strains, namely CPE2 and CPE3, were selected from MIXE1: CPE2, re ferred to the Pseudomonas genus, was found to be capable of totally de grading both 2-CBA and 2,5-dCBA, whereas Alcaligenes strain CPE3 was c apable of mineralizing 3-, 4-CBA and 3,4-dCBA. Substrate uptake studie s carried out with whole cells of strain CPE2 suggested that 2-CBA was metabolized through catechol, while 2,5-dCBA was degraded via 4-chlor ocatechol. 3-CBA, 4-CBA, and 3,4-dCBA appeared to be degraded through 3,4-dihydroxybenzoate by the CPE3 strain. MIXE1, which is capable of d egrading several chlorobenzoates, should therefore be able to minerali ze a number of low-chlorinated congeners of simple and complex polychl orinated biphenyl mixtures.