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.
