Year of Publication

2014

Degree Name

Master of Chemical Engineering (MChE)

Document Type

Master's Thesis

College

Engineering

Department

Chemical and Materials Engineering

First Advisor

Dr. Barbara L. Knutson

Abstract

The cost of deconstructing cellulose into soluble sugars is a key impediment to the commercial production of lignocellulosic biofuels. The use of the quartz crystal microbalance (QCM) to investigate reaction variables critical to enzymatic cellulose hydrolysis is investigated here, extending previous studies of fungal cellulase activity for the first time to whole cell cellulases. Specifically, the activity of the cellulases of Clostridium thermocellum, which are in the form of cellulosomes, was investigated. To clearly differentiate the activity of free cellulosome and cell-bound cellulosome, the distribution of free cellulosome and cell-bound cellulosome in crude cell broth at different growth stages of C. thermocellum (ATCC 27405) was quantified. Throughout growth, greater than 70% of the cellulosome in the crude cell broth was unattached to the cell. The frequency response of the QCM was shown to capture adsorption and hydrolysis of amorphous cellulose films by the whole-cell cellulases. Further, both crude cell broth and free cellulosomes were found to have similar inhibition pattern (within 0 - 10 g/L cellobiose). Thus, kinetic models developed for the cell-free cellulosomes, which allow for more accurate interfacial adsorption analysis by QCM than their cell-attached counterparts, may provide insight into hydrolysis events in both systems.

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