The surface active properties of the culture filtrates (from shake flask fermentation for 140 h at 37 +/- 1 degrees C) of a species of Micrococcus are described in terms of surface tension, emulsification and foamability using carbon sources, such as n-dodecane, n-tetradecane, n-hexadecane and n-octadecane as the different n-alkanes, adn sucrose, fructose, glucose and mannose as the different sugars. The surface tension for the culture filtrate was lowest with dodecane (45.2 mN m(-1)) followed by tetradecane (49.1 mN m(-1)), hexadecane (50.8 mN m(-1)) and octadecane (58.3 mN m(-1)) among the n-alkanes; for the sugars, sucrose had the lowest value (51.4 mN m(-1)) followed by fructose (52.8 mN m(-1)), mannose (57.3 mN m(-1)) and glucose (57.5 mN m(-1)). All the n-alkane systems showed 70-80% emulsification of a test mixture composed of equal volumes of kerosene and the respective culture filtrate. But only 84 and 50% of the formed emulsions with tetradecane and dodecane, respectively, remained stable during 48 h of ageing. Although the culture filtrate of fructose showed the highest initial emulsification of 62% among the sugars, almost no decay of the formed emulsion (41%) was observed with that of sucrose. Foamability noted with a single nozzle spurger was appreciable with the sucrose and fructose systems, but negligible with the n-alkane systems.