The potential of Jatropha curcas seed oil for biodiesel production is well recognized. Lipase transesterification of triglycerides is an eco-friendly alternative to chemical process. However, intoxication by methanol hampers further applicability of enzymatic transesterification. This study investigated the impact of methanol adding on transesterification efficiency for jatropha oil with methanol from 40 to 60 degrees C. For stepwise addition, the conversions by using methanol were from 33 to 42% at 24 h. For continuous addition, the conversions by using methanol were from 47 to 64%. Higher empirical first-order rate constants and favorable energetics for the first 6 h also demonstrated the advantages of the gradient addition over stepwise addition. Faster ME conversion for palmitic acid (C16:0) of jatropha oil was found, as well as the negative impact of double bonds of linoleic acid (C18:2) on methanolytic transesterification by both adding methods. (C) 2012 Elsevier Ltd. All rights reserved.