Immobilization of Beauveria bassiana lipase on silica gel by physical adsorption

Abstract

Extracellular lipase from Beauveria bassiana strain CG481 was immobilized by using thirteen different immobilization protocols. Silica gel was chosen as the most suitable adsorbent with 94.8% of activity yield. The adsorption on silica gel did not change the optimum pH (8.5) and temperature (45°C) values of the free lipase (FL) for lipolytic activity, and it showed higher activities in extreme conditions (pH 9.0 to 10.5, 60°C). The lipase immobilized on silica gel (ILS) showed enhanced stability at pH 7.0 after 120 h incubation (69.0%) when compared to FL (33.3%). The thermal stability was also enhanced by immobilization at 60°C in aqueous (64.6%) and organic medium (95.1%), while FL showed only 40.6% of residual activity in aqueous medium and exhibited no activity for esterification reaction in n-heptane. The treatment of ILS with 0.8 M NaCl prevented lipase desorption while Triton X-100 (0.1%) resulted the enzyme leakage. The ILS was reused for four times for esterification reaction with 80.8% of initial activity.