FUNGAL STRATEGIES FOR DETOXIFICATION OF MEDIUM-CHAIN FATTY-ACIDS

Fungi can degrade free fatty acids and triacylglycerols to provide a carbon and energy source. Medium chain fatty acids (those with a carbon length between six and 12 carbon atoms) are relatively uncommon. They are found in three oils of commercial importance-coconut, palm kernel and butter. The ability of fungi to convert medium chain fatty acids or triacylglycerols containing these acids to methyl ketones one carbon atom less has been known for a long time. Five genera can undertake these bioconversions-Aspergillus and Penicillium, and their corresponding teleomorphic genera Trichoderma, Cladosporium and Fusarium. Medium chain fatty acids inhibit fungal growth. The degree of inhibition depends on the concentration of the un-ionised acids. A number of fungal bioconversions of medium chain fatty acids can occur leading to the production of volatile metabolites. These include a partial beta-oxidation to give the methyl ketone one carbon atom less than the parent fatty acid, reduction of the ketone to give the secondary alcohol, hydroxylation of the ketone to give a mono-hydroxy ketone, esterification and decarboxylation. It is suggested that the production of these volatile metabolites is a fungal strategy to eliminate metabolites which would otherwise be toxic.