Side-chain degradation of certain ω-phenoxyalkanecarboxylic acids byNocardia coeliacaand other micro-organisms isolated from soil

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Abstract
Five micro-organisms were isolated from a garden soil by a selective culture technique in which ϵ -(2:4:5-trichlorophenoxy) caproic acid was used as sole carbon source. The capacity of these organisms to degrade the side-chain of certainω-plienoxyalkanecarboxylic acids C6H5O(CH2)nCOOH was then determined using chromatographic methods for the separation of the products of metabolism. Three of the organisms, viz.Nocardia coeliaca, Pseudo­monassp. andMicrococcussp. were found to effect side-chain breakdown readily. All the subsequent investigations here reported were carried out withN. coeliaca.Tenω-phenoxyalkanecarboxylic acid homologues were incubated with this organism and the chromato­graphic pattern was shown to be consistent withβ-oxidation, some hindrance being apparent with shorter chain lengths. In addition, with those homologues containing 9 and 10 methy­lene groups, there was evidence of another type of breakdown which could arise from anα-oxidation mechanism which Stumpf has shown to operate with fatty acids of a certain chain length. Phenol was not detected in metabolized solutions of any of the phenoxy homologues. The cells of the organism, however, which had been incubated with the pro­pionic, valeric or heptanoic acids (n= 2, 4 or 6), i. e. those acids theoretically able to yield phenol byβ-oxidation, were found to have an increased capacity for metabolizing phenol. It was therefore concluded that phenol is, in fact, produced in the metabolism of these phenoxy acids byN. coeliaca.Metabolism experiments were also carried out with members of six homologous series of chloro-substituted phenoxyalkanecarboxylic acids. The corresponding phenol was estimated in solutions after metabolism in each case and the results were readily explicable in terms ofβ-oxidation of the side-chain. The breakdown patterns on chromatograms were also typical of this type 'of oxidation. Certain types of ring substitution were shown to hinderβ-oxidation in a manner to that found in our earlier investigations in which wheat coleoptile and pea stem tissues were used.

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