The monoethyl esters of the long chain fatty acids (biodiesel) were prepared by alcoholysis of Jatropha oil, a non-edible oil, by a lipase. The process optimization consisted of (a) screening of various commercial lipase preparations, (b) pH tuning, (c) immobilization, (d) varying water content in the reaction media, (e) varying amount of enzyme used, and (f) varying temperature of the reaction. The best yield 98% (w/w) was obtained by using Pseudomonas cepacia lipase immobilized on celite at 50 degrees C in the presence of 4-5% (w/w) water in 8 h. It was found that yields were not affected if analytical grade alcohol was replaced by commercial grade alcohol. This biocatalyst could be used four times without loss of any activity. (c) 2006 Elsevier Ltd. All rights reserved.