The activity of lipase from Humicola lanuginosa was investigated at the cubic liquid-crystalline phase/water interface. For comparison, the activity of this lipase at an ordinary triglyceride/water interface was also determined. A cubic phase was formed by monoolein and water, and triolein was used as reference. The sample were weighed into glass ampoules, lipase solution was added, and lipolysis was followed by visual observation and by photographing the sample at given time intervals (1 min, 30 min, 3 h, 9 h, and 24 h). Experiments were performed with lipase at a concentration of 0.2 mg/ml (6 muM) dissolved in distilled water and in buffers at pH 5, 7, and 10. At the end of the experiments, thin layer chromatography (TLC) was used to determine the composition of the samples. The results showed clear lipolysis in distilled water (pH 5 at the end of the experiments) and in buffers at pH 5 and 10. After approximately 30 h these samples were decomposed to oleic acid arid glycerol. (C) 1994 Academic Press, Inc.