Adsorption and activity of cellulase enzymes on various cellulose substrates.

摘要

The objective of this research is to understand the interfacial behavior in cellulose hydrolysis by cellulase enzymes. This research began with an investigation on the in-situ monitoring of cellulose hydrolysis using a piezoelectric quartz crystal microbalance. The real-time kinetic behavior was modeled using a dose-response model. The adsorption indicated by the drop in resonance frequency followed a Langmuir model. Another important part of this research was the development of a new cellulase activity assay based on the piezoelectric technique. This assay provides an easier and more user-friendly method to measure cellulase activity. It also helped to clarify an element in the interpretation of frequency shift after injection of cellulase solutions for the hydrolysis of cellulose thin films, which has been neglected in previous efforts. Interfacial adsorption of cellulase proteins was also investigated using the depletion method. The effects of substrate properties, primarily the crystallinity, which was characterized using X-ray diffraction, were investigated. The effect of surface areas, which were measured using laser light scattering and BET gas adsorption techniques, on cellulase adsorption were also investigated. It was found that both crystallinity and surface areas played an important role in cellulase adsorption on the substrates studied. In the characterization of cellulosic substrates, the water retention value was also investigated. The results indicated that substrates with lower crystallintiy had higher water retention ability. The cellulase adsorption and desorption were also studied by using sodium dodecyle sulphate polyacrylamide gel electrophoresis (SDS-PAGE). The adsorption results followed the same trend as indicated by the depletion methods. The various isozymes demonstrated a uniform adsorption and desorption in proportion to their concentrations. Higher pH was found to produce higher desorption for the cellulases and substrates studied. It was also found that cellulases from Trichoderma reesei had higher affinity than those from Aspergillus niger in terms of their affinity with the cellulosic substrates used in this work.