The synthesis of a green clean biosolvent, isopropyl esters, using high-oleic sunflower oil (HOSO) as raw material over an enzymatic catalyst, has been developed and optimized following a factorial design and response surface methodology. A full three-factorial design has proved effective in the study of the influence of the variables (temperature, enzyme concentration, and alcohol/oil molar ratio) on the process. The process was studied in the range of 68-82 degrees C, 1.8-8.4% wt. catalyst concentration, and initial alcohol/oil molar ratio 1: 1-11: 1. The molar ratio of alcohol/oil was been found to be the most significant factor on the transesterification process and its influence is negative. The response surface model obtained, representing the yield of ester, was found to describe adequately the experimental results. The best conditions for the process are a catalyst concentration of 7%, an operation temperature of 71 degrees C and with low alcohol/oil molar ratio (3: 1); with these conditions the maximum conversion obtained was 84%. The preparation of the product is a green engineering process, clean, solvent-free, with a very selective catalyst that minimizes water and energy consumption and the downstream processing of the integrated process. (c) 2007 Elsevier Inc. All rights reserved.