Improved efficiency of lipase-mediated epoxidation of α-pinene using H2O2 in single-phase systems

Abstract

Taking advantage of the intersolubility of alcohol and water, we developed an efficient single-phase system for chemoenzymatic epoxidation of (-)-α-pinene. Different from traditional methods, it included all substrates, such as (-)-α-pinene, acyl donors and oxidants, into one phase. Isopropanol was eventually selected as the epoxidation medium to optimize three controllable parameters. Under the optimal conditions of 3.35 mol/L ethyl acetate and 1.1 mol/L H2O2, the conversion and selectivity reached 92.3% and 86.6% in 90 min, respectively, and the initial reaction rate was 13.58×10−4 mmol·min−1·mg−1 with Novozym435 as a catalyst. Trisodium citrate was screened as an acid-trapping reagent to eliminate the negative impact of acetic acid on (-)-α-pinene oxide. The enzyme reusability was at least 6 cycles with a relative activity of 57.5% at the sixth cycle.