Surface and physico-chemical properties of a glycolipid biosurfactant, mannosylerythritol lipid, from Candida antarctica

Candida sp. SY16 produces a glycolipid-type biosurfactant, mannosylerythritol lipid (MEL-SY16) which, at low concentrations, emulsifies hydrocarbons, vegetable oil, and crude oil. The molecular weight of MEL-SY16 was 634 Da and its hydrophilic lipophilic balance (HLB) was 8.8. It decreased the surface tension to 30 dyne cm 1 at a critical micelle concentration (CMC) of 15.8 muM, and the minimum interfacial tension against kerosene (a mixture of petroleum hydrocarbons) was 0.1 dyne cm(-1). MEL-SY16 was stable from pH 4 to pH 10, up to 90 C for 1 h, and against NaCl up to 100 mM. It was readily degraded by microorganisms in activated sludge within a short time, and exhibited very low toxicity to mouse fibroblast cells. These properties confirm that MEL-SY16 is suitable for a variety of environmental applications.