Hydrolysis of carboxymethyl cellulose catalyzed by cellulase immobilized on silica gels at low and high pressures

Cellulase from Humicola insolens was encapsulated in hydrophilic silica aerogels by sol-gel procedure and supercritical carbon dioxide (SC CO2) drying. Such on aerogel immobilized cellulase was used as biocatalyst for hydrolysis of carboxymethyl cellulose (CMC) in aqueous medium at atmospheric pressure and in high-pressure system CO2/H2O. Influence of different reaction parameters, such as biocatalyst concentration and temperature on enzyme-catalyzed hydrolysis of CMC, were studied. As the major advantage of immobilized enzymes is easier separation from the product solution the reusability studies of immobilized enzyme preparation were performed at atmospheric pressure and in system CO2/H2O at pressure of 10 MPa. The immobilized cellulase was successfully reused for more than 20 times without any significant loss of activity. Thermal stability studies of immobilized and crude cellulase in SC CO2 showed that the activity of in SC CO2 pre-incubated immobilized cellulase was much higher than the activity of crude cellulase exposed in SC M at the same conditions. The residual activity of pre-incubated on aerogel immobilized cellulase at 111 degrees C was 172%. (C) 2007 Elsevier B.V. All rights reserved.