Production of n-Propyl Cinnamate (Musty Vine Amber Flavor) by Lipase Catalysis in a Non-Aqueous Medium

Abstract

The enzymatic esterification of n-propanol with cinnamic acid was carried out with a commercial lipase (Lipolase 100T) immobilized onto silica. The silica pretreated with 1% (v/v) glutaraldehyde showed 95% protein binding efficiency. Esterification reactions were carried out at 45oC under shaking (160 rpm) with 75 mM: 100 mM of cinnamic acid and n-propanol, respectively in DMSO. The maximum yield of n-propyl cinnamate (94 mM) was achieved in 2.5 h at 45oC using 25 mg of silica-bound biocatalyst. Addition of molecular sieves to the reaction mixture had little effect in improving the ester synthesis. In esterification reaction among the tested salt ions, a pre-exposure of the silica-bound lipase to Ca2+ and Cu2+ ions (1 mM) improved the ester yield in DMSO. The silica-immobilized lipase retained ~39% of its original efficiency after 7th repetitive cycle of esterification. The n-propyl cinnamate synthesis when scaled up to 50 ml batch reaction yielded 79 mM of the ester. Thus the study achieved a good yield of n-propyl cinnamate synthesis in DMSO in a scaled-up reaction system under optimized conditions using silica-bound lipase. Keywords: Cross-linking, esterification, glutaraldehyde, immobilization, lipase, n-propyl cinnamate, DMSO, silica-bound lipase, carboxyester, esterases, lipases, mono-acylglycerols, glycerol, fatty acids