Candida antarctica synthesised surface-active mannosylerythritol lipids at 46 g l(-1) by adding 80 g soybean oil l(-)1 to the medium and maintaining the pO(2) at 50% with an air flow rate 1 vvm. Two-stage culturing of C. antarctica avoided medium foaming but the yield of biosurfactants synthesis was 28 g l(-1). The biosurfactants decreased the surface tension of water to 35 mN m(-1).