Enzymatic synthesis of geranyl acetate by transesterification with acetic anhydride as acyl donor

Pseudomonas sp. lipase (PS) was immobilized by adsorption technique onto glass beads and tested for its ability to synthesize geranyl acetate by transesterification with acetic anhydride as the acyl donor. Reactions were carried out inn-hexane containing 0.1 M geraniol, 0.1 M acetic anhydride, and 200 units of lipase PS. Enzyme load, effect of substrate concentration, added water, temperature, time course, organic solvent, pH memory, and enzyme reuse were studied. Yields of up to 96% were obtained with 200 units (approximately 11% w/w of reactants) of enzyme. Increasing amounts of geraniol inhibited lipase activity, while excess acyl donor concentration enhanced ester production. Yields as high as 97% were obtained at 50°C, 24 h incubation, with no added water. Solvents with logP values ≥3.0 showed the highest conversion yields. Solvent-free samples also performed well. The pH range of 4–9 gave good yields (92–98.4%). Enzyme reuse studies showed the lipase remained active after 15 runs.