Cellulase immobilized by sol-gel entrapment for efficient hydrolysis of cellulose.

Cellulase from Trichoderma reesei (Celluclast 1.5 L, Novozyme) was immobilized by sol-gel encapsulation, using binary or ternary mixtures of tetramethoxysilane (TMOS) with alkyl- or aryl-substituted trimethoxysilanes as precursors. Optimization of immobilization conditions resulted in 92 % recovery of total enzymatic activity in the best immobilized preparate. The immobilized cellulase exhibiting the highest activity, obtained from tetramethoxysilane and methyltrimethoxysilane precursors at 3:1 molar ratio, was investigated in the hydrolysis reaction of microcrystalline cellulose (Avicel PH101). Although the optimal values did not change significantly, both temperature and pH stabilities of the sol-gel entrapped cellulase improved compared to the native enzyme. Immobilization also conferred superior resistance against the inactivation effect of glucose. Reuse of the sol-gel entrapped cellulase showed 40 % retention of the initial activity after five batch hydrolysis cycles, demonstrating the potential of this biocatalyst for large-scale application.