Lipase activity in dormant seeds of the African oil bean (Pentaclethra macrophylla Benth)

Acetone powders were obtained from freshly harvested dormant seeds of African oil bean (Pentaclethra macrophylla Benth) and the activity as well as substrate specificity of the isolated crude lipase (glycerol ester hydrolase E.C. 3.1.1.3) were examined. The enzyme was more active on lauric oils (containing short-chain fatty acids), especially coconut oil. Hexane at 1:2 v/w solvent:substrate ratio was optimal in enhancing lipolysis of the oils. Optimum substrate concentration was 5 g in 2.5 ml of solvent, above which enzyme inhibition resulted. Lipolysis increased with enzyme concentration (non-linearly), with optimum rate at between 0.5 and 0.75 g and 60 min incubation. Optimum temperature for the activity of the oil bean lipase was 30 °C, although substantial lipolysis was still evident at 80 °C indicating the fairly high thermostability of the enzyme. pH optimum for enzyme activity was near neutrality. The effects of different ions on the activity of the isolated lipase were also investigated. The presence of Ca2+ increased activity by 64% while sodium chloride and mercuric chloride inhibited activity by 36% and 28.5%, respectively. On addition of EDTA, an inhibition in activity of 28% was observed. The results of the present study show that the oil bean seed will deteriorate with storage.