Total Degradation of 4-Chlorobenzoic Acid by an Acinetobacter sp.

Abstract

An organism isolated from a soil sample with 4-chlorobenzoic acid (4-CBA) as the sole carbon and energy source was tentatively identified as an Acinetobacter sp. This organism, strain ST-1, could completely mineralize 4-CBA in pure culture. The strain hydrolytically dehalogenated 4-CBA as the first step in the degradation pathway. The product, 4-hydroxybenzoic acid, was further metabolized via protocatechuic acid (PCA) under aerobic conditions. The conversion of 4-CBA into 4-hydroxybenzoic acid occurred with a yield greater than 80% under anaerobic conditions with continuous passage of nitrogen into the culture, so molecular oxygen was not essential for dehalogenation. Spectrophotometrical studies showed that the strain oxidized PCA to form β-carboxy-cis, cis-muconic acid as the ortho-ring fission product. Cell extracts converted PCA to β-ketoadipic acid, which was evidence that PCA was cleaved by ortho fission and further degraded in the β-ketoadipate pathway.