Improved fluorometric method to assay for soil lipase activity

Optimum conditions for the precise assay of soil lipases are described, using the fluorogenic substrate 4-methyl umbelliferone nonanoate (4MUN). The method utilizes a 3 h 0.1 m tetra-sodium pyrophosphate (pH 7.5) extraction, followed by a 10 min assay. Soil lipase is measured with average 95% confidence limits of 5.6%. Activity was optimal between 30–40°C. Soil extracts characteristically possessed two pH-activity peaks, one each side of neutrality. Extracts were stable when stored at 4°C for at least 5 days.