Presenter: Changwoo Jeong
Advisor(s): Orlando J. Rojas
Author(s): Changwoo Jeong, Dimitris S. Argyropoulos
Graduate Program: Wood and Paper Science

Title: Degradation of Nano-scale Films of Cellulose and Lignin by Using Piezoelectric Resonators

Abstract: In this investigation we examined the interfacial behavior of cellulase and laccase active enzymes on thin films of cellulose and lignin. Typical films were prepared by spin coating techniques with resultant thicknesses of the order of 15 nm. By using a Quartz Crystal Microbalance (QCM) with mass sensitivity of less that 1 ng/cm2 it was possible to monitor in-situ and in real time the dynamics of film degradation. After exposure of the films to the respective enzymes we observed three distinctive phases. The initial phase involved the adsorption and binding of the enzyme on the surface. The piezoelectric frequency and dissipation data were fitted to simple kinetic models and the rate of adsorption and maximum adsorbed amount were calculated. In an intermediate phase a reduction of the resonant frequency of the sensor indicated film degradation. The slope was taken as indicative of the rate of degradation. The final, phase involves slower rate processes during the exhaustion of the film. The dynamics of the process was studied at different enzyme concentrations and different solution temperature and pH. Issues related to mass transport effects in the reaction chamber were also investigated. Overall, it is demonstrated the potential of piezoelectric resonators to characterize and monitor the kinetics of enzyme activity at the nanoscale for lignocellulosic substrates, adding another dimension to our knowledge and the methods available for such enquiries.