Biodegradation of a high molecular weight aliphatic ether--indications of an unusual biodegradation pathway

An aliphatic ether (1-phytanyl-1-octadecanyl-ether) of high molecular weight was used as a sole carbon source in degradation experiments with different aerobic bacteria. The enriched culture B5, obtained from fuel contaminated soils, was able to degrade the substance for more than 90%. A culture of Rhodococcus ruber was similarly effective. Detailed investigation of the metabolites allowed us to characterize an unusual degradation pathway via a mid-chain oxidation mechanism ('internal oxidative pathway'). Obviously, formation of intermediate alkenes mainly at the unbranched side chain was a prerequisite for bacterial degradation of the added substrate. Degradation proceeded - in spite of the usually preferred terminal oxidation - via oxidation of the internal double bond and was followed by an ester cleavage. In turn, a series of alcohols was formed which were subsequently oxidized to the respective carboxylic acids and were further metabolized via the normal beta-oxidation pathway.