Improved activity and stability of Rhizopus oryzae lipase via immobilization for citronellol ester synthesis in supercritical carbon dioxide

In present work, Rhizopus oryzae lipase immobilized on a film prepared using blend of hydroxylpropyl methyl cellulose (HPMC) and polyvinyl alcohol (PVA) was investigated for synthesis of citronellol esters with supercritical carbon dioxide (Sc-CO2) as a reaction medium. The transesterification reaction was optimized for various reaction parameters like effect of molar ratio, acyl donor, time, temperature, enzyme concentration, effect of pressure and co-solvent to achieve the maximum yield of desired product. The results obtained signify remarkable increment (about eightfold) in the yield of citronellol acetate (91%) as compared to that of free lipase (11%) in Sc-CO2. The developed biocatalytic methodology provides a substantial advantage of low biocatalyst loading (1.5%, w/v), lower reaction temperature (45 degrees C) and lower pressure (8 MPa) as compared to previous reports. The immobilization method has significantly enhanced the operational stability of lipase for ester synthesis under Sc-CO2 conditions. The developed methodology was successfully applied for synthesis of three different industrially important citronellol esters namely citronellol acetate (91%), citronellol butyrate (98%), citronellol laurate (99%) with excellent yields using vinyl esters as acyl donor under Sc-CO2 conditions. In addition, the immobilized biocatalyst was effectively recycled for three consecutive recycles. (C) 2011 Elsevier B.V. All rights reserved.