Surface active properties of the culture filtrates of a Micrococcus species grown on n-alkanes and sugars

The surface active properties of the culture filtrates (from shake flash fermentation for 140 h at 37 ± 1°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, and 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.