Microbial metabolism of alkylbenzene sulphonates. Variance in enzyme complement of a Bacillus in response to growth substrate.

Growth of a Bacillus species at the expense of an alkylbenzene sulphonate (ABS) synthetic detergent homologue (1-phenylundecane-p-sulphonate, 11-ABS) containing an odd number of carbon atoms in the alkyl side chain induced an enzyme complement able to biodegrade 11-ABS by alkyl side-chain oxidation, and "ortho cleavage" aromatic-ring oxidation reactions. Growth of the Bacillus at the expense of an ABS homologue containing an even number of carbon atoms in the alkyl side chain (1-phenyldodecane-p-sulphonate, 12-ABS) induced an enzyme complement able to biodegrade 12-ABS by alkyl side-chain oxidation, and "meta cleavage" aromatic-ring oxidation reactions. The results of a number of different growth and enzyme induction experiments confirm that both 11-ABS and 12-ABS are initially biodegraded by an identical complement of enzymes catalysing the alkyl-side-chain oxidation reactions, but that the subsequent metabolism of the aromatic moieties remaining after the removal of the alkyl side chain from 11-ABS and 12-ABS occurs by two separate pathways requiring the de novo induction of different substrate-specific enzyme complements. The detection of the predicted changes in enzyme complement subsequent to changes in the growth substrate of the Bacillus provide confirmation of the biodegradation pathways operating in the microorganism.