Preparation of Surfactant-Coated Lipase for the Esterification of Geraniol and Acetic Acid in Organic Solvents

Abstract

Lipolytic esterification of geraniol and acetic acid in an organic solvent was investigated. A surfactant-coated lipase (SCL) was designed to enhance the esterification. The ester product, geranyl acetate, is an important component of flavor and fragrance compounds. Fatty acids such as acetic acid cause substantial deactivation of lipase, resulting in low esterification yields. SCL is expected to prevent direct contact of organic solvent and the substrates with lipase, thereby decreasing enzyme deactivation. The lipase from Candida cylindrecea interacted with the surfactant Span 85 in a buffer of pH 5.2 to form SCL for the esterification of geraniol and acetic acid. The SCL possessed low solubility in organic solvents which is beneficial for the recovery and repeated usage of enzyme. At the condition of [geraniol]/[acetic acid] = 2, lipase/surfactant = 0.5 and in isooctane at 35°C, the esterification yields after 24 and 36 h were 83.7 and 97%, respectively, which were much higher than those obtained by using reverse micelles and powdered lipase. The organic solvent had a dramatic effect on the esterification yield. The polarity of the product, substrate, and organic phase were used as the criteria for solvent selection. The SCL was easy to prepare, could be repeatedly used, and exhibited long-term stability. The esterification efficiency remained unchanged after nine days of use.