Lipase entrapment in protamine-induced bio-zirconia particles: characterization and application to the resolution of (R,S)-1-phenylethanol.

Lipase from Burkholderia cepacia was encapsulated inside zirconia particles by biomimetic mineralization of K₂ZrF₆ induced with protamine, a natural cationic protein. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Fourier transform infrared spectroscopy (FT-IR) were employed for the characterization of the novel immobilized lipase. SEM and TEM images showed that both the zirconia particles with and without lipase have good spherical structures with average particle sizes of 150 nm. Fluorescence microscopy demonstrated that the lipase was indeed encapsulated inside the zirconia particles. The maximum immobilization capacity of the zirconia particles was 0.15 units/mg under optimum immobilization conditions. Biochemical characterization showed that the encapsulated lipase could retain most of its initial activity. Compared with free lipase, the encapsulated lipase exhibited improved thermal, pH, and recycling stabilities. After 8 weeks of storage, no substantial loss in catalytic activity was observed for the encapsulated lipase. The conversion of the kinetic resolution of (R,S)-1-phenylethanol with vinyl acetate as acetyl donor catalyzed by zirconia-immobilized lipase reached 49.9% with higher ee(s) of 99.9% under the following optimal conditions: octane as solvent, 0.1M (R,S)-1-phenylethanol, 70 mg immobilized lipase, 180 rpm, 50 °C for 48 h. After 6 cycles (288 h), the conversion and ee(s) were still 43% and 85%, respectively.