DEGRADATION OF CHLOROBENZOATES IN SOIL SLURRY BY SPECIAL ORGANISMS

The microbial degradation of 2-chloro-, 3-chloro-, 4-chloro-, 3,4-dichloro- and 3,5-dichlorobenzoate was examined either as single compounds or as mixtures in soil slurry. The influence of water content, rotation frequency, supplementation of mineral salts and acetate and the addition of specialized bacterial cultures (Pseudomonas sp. strain B13, P. ruhlandii strain WR912, P. cepacia strain JH230) to the soil on the degradation rate was studied. Only 4-chlorobenzoate was completely degraded within 17 days by the original soil population. In contrast, the total degradation of all other compounds, i.e. stoichiometric elimination of chloride, was only observed when specialized organisms were inoculated into the soil slurry. Small amounts of specialized bacteria (500 colony-forming units/ml) led to rapid and complete degradation. Even 3,4-dichlorobenzoate, which cannot be used by our strains as a growth substrate, was degraded in a mixture with other chlorobenzoates. Nitrite, which sometimes appeared during the incubations, inhibited the degradation.