(192l) Enzymatic Hydrolysis of Spin Coated Regenerated Cellulose Thin Films Studied with a Quartz Crystal Microbalance
During the last decade considerable effort has focused on understanding the mechanism of action of the cellulase enzymes, optimization of the enzyme mixture to result in maximum sugar yield and development of a comprehensive kinetics model to describe the hydrolysis process. However, a main difficulty (due to lack of experimental techniques) in studying enzymatic hydrolysis lies in directly measuring the amount of enzyme adsorbed onto the cellulose and the resultant hydrolysis rates. Recent developments in manufacture of thin cellulose films and in experimental techniques have helped overcome these difficulties. The aim of this thesis is to use a novel experimental technique - Quartz Crystal Microbalance with Dissipation monitoring (QCM-D) to study cellulose hydrolysis by different cellulases. Thin films of cellulose were successfully fabricated on gold crystals for hydrolysis study. Hydrolysis was carried out by three different cellulases: AccelleraseTM 1000, AccelleraseTM 1500 and Spezyme® CP; at different activities. The amount of enzyme adsorbed, the viscoelastic nature of the cellulose film and the subsequent hydrolysis rates were directly measured under different enzyme activities. It was found that the three enzymes had the same affinity for the cellulose film and that the cellulose thin films were hydrolyzed at a constant rate which was directly proportional to the amount of enzyme adsorbed. The measured specific rates for AccelleraseTM 1000 and Spezyme® CP were similar but AccelleraseTM 1500 was found to have a lower specific rate. This suggests that AccelleraseTM 1000 and Spezyme® CP had a similar composition of endo and exo glucanases but the concentration of these enzymes in AccelleraseTM 1500 composition was lower.