Interactions between fungal cellulases and films of nanofibrillar cellulose determined by a quartz crystal microbalance with dissipation monitoring (QCM-D)

Understanding the interactions between enzymes and substrates and the property changes of the substrates during the process is vital for efficiently producing fuels and chemicals from lignocellulosic biomass. In this manuscript, quartz crystal microbalance with dissipation (QCM-D) technique was employed as a tool to investigate the adsorption and hydrolysis behaviors of four fungal cellulases (Trichoderma reesei, Trichoderma viride, Aspergillus sp. and Aspergillus niger) on the substrate of nanofibrillar cellulose (NFC) film. The characterization of the cellulose films before and after enzymatic treatment was represented by atomic force microscopy. The results showed that four cellulases behaved quite differently. The cellulases from T. reesei and T. viride adsorbed onto NFC films and then the hydrolysis was carried out; and their trends represented by different overtones were similar and consistent. The cellulase from Aspergillus sp. adsorbed on the substrate to form a quite compact layer since substantial frequency changed with little dissipation variation. In term of the cellulase from A. niger, its frequency and dissipation overtones exhibited diverged behaviors. After viscoelastic modeling for cellulases except for Aspergillus sp using the multi-overtone data provided by QCM-D technique, the film properties of NFC film and adlayer were extracted and they could help to understand the interactions between cellulases and substrates.