Enhancing indigenous lipase activity of germinated Jatropha curcas L. Seeds for the enzymatic degradation of phorbol ester

• Lipase activity was enhanced by seed soaking at pH 6 for 12 h without aeration.
• Slightly acid or alkali condition inhibited germination and induced lipase activity.
• Phorbol esters (PE) were degraded during germination.
• Enzymatic treatment effectively reduced PE content in the Jatropha seed cake.
• Incubation for 12 h was enough to fulfil the requirement of a non-toxic cake.

Both the unique substrate specificity of plant lipases and the enzymatic degradation of phorbol esters (PE) have not been studied extensively. The objectives of the research were to improve the indigenous lipase activity of germinated Jatropha seeds and its specificity in the enzymatic PE degradation. Factors that influence the lipase activity of germinated seeds, such as, the effect of the soaking buffer pH, soaking time, growing stage, and aeration during soaking were evaluated. Furthermore, the effects of the growing stage, reaction time, and the amount of enzymes on PE degradation were also evaluated. Results show that stress conditions by changing the soaking buffer pH from neutral into slightly acidic or alkaline conditions inhibited seed germination but induced the lipase production. The highest lipase activity was obtained from growing stage 4, in which the seeds were soaked at pH 6 for 12 h without aeration. Aeration reduced lipase activity about 19.5 times. On the other hand, PE was degraded during germination. The highest activity of germinated seed lipase for PE degradation was also obtained from growing stage 4. Degradation of PE in the Jatropha cake using 10 U for 12 h was enough to fulfil the requirement of a non-toxic Jatropha seed cake.