ETHEROLYTIC CLEAVAGE OF 4-(2,4-DICHLOROPHENOXY)BUTYRIC ACID AND 4-(4-CHLORO-2-METHYLPHENOXY)BUTYRIC ACID BY SPECIES OF RHODOCOCCUS AND AUREOBACTERIUM ISOLATED FROM AN ALKALINE ENVIRONMENT

Bacterial strains were isolated from the concrete rubble of a demolish ed herbicide production plant. The predominant feature of these strain s was the etherolytic cleavage of 4-(2,4-dichlorophenoxy)butyric acid (DCPB)(1)) and 4-(4-chloro-2-methylphenoxy)butyric acid (MCPB) while l iberating 2,4-dichlorophenol (DCP) and 4-chloro-2-methylphenol (MCP) r espectively. Some of the isolates were identified by 16S rDNA sequence analysis and shown to belong to the genera Aureobacterium sp. (strain K2-17) and Rhodococcus (Rh. erythropolis K2-12). The other strains is olated clustered into these two groups according to fatty acid analysi s. Etherolytic cleavage proceeded under neutral to alkaline conditions with an optimum at around pH 8.5. With Aureobacterium sp. No. K2-17, the degradation rate was zero at a pH of 6 but as much as 60% of the m aximum activity was observed at pH 10.5. With Rh. erythropolis K2-12, by contrast, pronounced activity was detected at pH 6.5 while degradat ion was no longer observed at pH 10.5. The maximum rates of cleavage w ere about 1 mmol DCPB/h . g dry mass with Aureobacterium sp. No K2-17 and about 0.6 mmol DCPB/h . g dry mass with Rh. erythropolis K2-12. DC PB and MCPB were utilized to the same extent. Substrate cleavage and p roduct formation (DCP) proceeded at almost equal rates with Aureobacte rium sp. No. K2-17 and Rh. erythropolis K2-12, which indicates that th is compound was not further metabolized. Only phenoxybutyric acid comp ounds served as substrates; phenoxyacetic acid and phenoxypropionic ac id derivatives were not utilized by these strains.