Enzymatic kinetics of cellulose hydrolysis: a QCM-D study

The interactions between films of cellulose and cellulase enzymes were monitored using a quartz crystal microbalance (QCM). Real-time measurements of the coupled contributions of enzyme binding and hydrolytic reactions were fitted to a kinetic model that described closely significant cellulase activities. The proposed model combines simple Boltzmann sigmoidal and 1 - exp expressions. The obtained kinetics parameters were proven to be useful to discriminate the effects of incubation variables and also to perform enzyme screening. Furthermore, it is proposed that the energy dissipation of a film subject to enzymatic hydrolysis brings to light its structural changes. Overall, it is demonstrated that the variations registered in QCM frequency and dissipation of the film are indicative of mass and morphological transformations due to enzyme activities; these include binding phenomena, progressive degradation of the cellulose film, existence of residual, recalcitrant cellulose fragments, and the occurrence of other less apparent changes throughout the course of incubation.