Lipase immobilization on O-propargyl and O-pentynyl dextrans and its application for the synthesis of click beetle pheromones

Lipase of Rhizopus arrhizus was immobilized on O-propargyl dextran (PgD) and O-pentynyl dextran (PyD). Compared with Lewatit VP OC 1600 cation ion exchange resin, wood shaves, fuller earth, silica and alumina, PgD with degree of substitution (DS) of 0.68 and a surface of 10 m2/g was found to be the most effective immobilization support and an excellent biocatalyst for esterification reactions in organic solvents as the synthesis of click beetle pheromone geranyl octanoate. PyD (DS 0.44) with a surface of 3.3 m2/g was of similar high efficiency. For the enzymatic esterification the optimum concentration of geraniol and octanoic acid was 0.4 mol L−1 each. The biocatalyst worked the best in hexane at a moisture level of 0.02%. The enzyme could be repeatedly used and conversion dropped from 80% to 70% after four cycles, while reaction rate even increased when repeatedly employed.