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Enzyme Research
Volume 2011, Article ID 718949, 8 pages
http://dx.doi.org/10.4061/2011/718949
Research Article

Synthesis of Isopropyl Ferulate Using Silica-Immobilized Lipase in an Organic Medium

Department of Biotechnology, Himachal Pradesh University, Summer Hill, Shimla 171 005, India

Received 11 November 2010; Revised 22 January 2011; Accepted 11 February 2011

Academic Editor: Alane Beatriz Vermelho

Copyright © 2011 Ashok Kumar and Shamsher Singh Kanwar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Immobilization of lipases has proved to be a useful technique for improving an enzyme's activity in organic solvents. In the present study, the performance of a silica-immobilized lipase was evaluated for the synthesis of isopropyl ferulate in DMSO. The biocatalyst was cross-linked onto the matrix with 1% glutaraldehyde. The effects of various parameters, molar ratio of ferulic acid to isopropyl alcohol (25 mM : 100 mM), concentration of biocatalyst (2.5–20 mg/mL), molecular sieves (25–250 mg/mL), and various salt ions, were studied consecutively as a function of percent esterification. Immobilized lipase at 25 mg/mL showed maximum esterification (~84%) of ferulic acid and isopropanol at a molar ratio of 25 mM : 100 mM, respectively, in DMSO at 45°C in 3 h under shaking (150 rpm). To overcome the inhibitory effect of water (a byproduct) if any, in the reaction mixture, molecular sieves (3 Å × 1.5 mm; 100 mg/mL) were added to the reaction mixture to promote the forward reaction. Salt ions like Ca2+, Cd2+, and Fe2+ enhanced the activity of immobilized biocatalyst while a few ions like Co2+, Zn2+, Mg2+, Mn2+, Al3+, and Na+ had mild inhibitory effect. Approximately, one third of total decrease in the esterification efficacy was observed after the 5th repetitive cycle of esterification.