Fig. 1

The proposed biological pathway for dicarboxylic acid (DCA) production in Wickerhamiella sorbophila. Alkanes are first oxidized to the corresponding fatty alcohol by a cytochrome P450 monooxygenase/cytochrome P450 reductase complex (CYP + CPR). The fatty alcohol is converted into a corresponding fatty aldehyde by fatty alcohol oxidase (FAO) or alcohol dehydrogenase (ADH). Then, the fatty aldehyde is oxidized to fatty acid (FA) by fatty aldehyde dehydrogenase (FALDH). FA methylester is hydrolyzed by extracellular lipase or esterase before primary oxidation, and its corresponding FA is converted to DCA via the same mechanism as alkane. Converted FA and DCA are finally degraded to acetyl-CoA by the successive reactions of acyl-CoA synthetase (ACS), acyl-CoA oxidase (POX), 2-enoyl-CoA hydratase (MFE), 3-hydroxyacyl-CoA dehydrogenase (MFE), and 3-ketoacyl-CoA thiolase (POT). To prevent the continuous catabolism of carboxylic acids to acetyl-CoA, β-oxidation-related genes, POX, are removed