Formation of Glycolipid Biosurfactant, Mannosylerythritol Lipid, by Candida antarctica from Aliphatic Hydrocarbons via Subterminal Oxidation Pathway

Abstract

In order to provide more available substrates other than just vegetable oils for producing the glycolipid biosurfactant, mannosylerythritol lipid (MEL), by Candida antarctica T-34, MEL productivity was examined using various aliphatic hydrocarbon substrates under resting-cell conditions. The yield of MEL varied considerably depending on substrate used. MEL was produced in significant amounts from 1-alkenes (C12 to C18), 2-alkanols and 2-alkanones (C12 to C14). These alkanols and alkanones gave higher yields of MEL than the corresponding 1-alkanols with the same carbon chain-length. Among hydrocarbon substrates examined, 2-tetradecanol gave the highest yield of MEL (>30g/L), that was comparable yield produced with tetradecanoic acid. A comparison between the fatty acid profiles of MEL obtained from 2-alkanol and 2-alkanone substrates revealed only slight differences. In contrast, significant differences were observed between those from 2-alkanone and 3-alkanone substrates. These results suggest that the conversion of 2-alkanols into fatty acids to give the glycolipid is accomplished by the operation of a subterminal oxidation pathway, which consists of the steps catalyzed by a secondary alcohol dehyrogenase, Baeyer-Villiger monooxygenase and esterase. This is the first report on the involvement of a Baeyer-Villiger type of oxidation in biosurfactant production.