Comparison of the performance of entrapped and covalently immobilized lipase in the synthesis of pear flavor

Abstract

Abstract Introduction Although aroma esters are produced mostly by a chemical method that requires the use of aggressive chemical catalysts, enzymatic esterification has been very favored during previous two decades. The main aim of this study was to investigate the commercially important pear flavor, hexyl acetate (HAc), by the catalysis of immobilized lipase samples and to optimize the immobilization and operational conditions in detail. Methods Lipases from Candida rugosa (CRL) and porcine pancreas (PPL) were immobilized using biodegradable polysaccharides, by entrapment in calcium alginate/chitosan composite gel (CRLCa-Alg/Chi and PPLCa-Alg/Chi) and by covalent binding onto the chitosan (CRLChi and PPLChi) carrier. Results Among the several organic media, the highest esterification activites were observed in heptane. HAc yield decreased when substrate concentrations were higher than 50 or 75 mM. Yield increased with increase in reaction time up to the 5th hour in the batch type reactor while it increased during the 8 h reaction time for fixed bed reactors with lower yields. Discussion and conclusions As well as synthesis conditions, immobilization parameters also affected HAc productivity. The amount of water in the microenvironment of lipase is so important not only for gaining its active conformation but only for the reaction direction.