Nonlinear microscopy and CP/MAS 13C-NMR as tools for studying structural changes of cellulosic substrates during enzymatic hydrolysis

Conference poster, 2015

Liberation of fermentable sugars from cellulosic biomass during the course of enzymatic hydrolysis is one of the major obstacles in biorefineries due to high cost of enzymes. Enzymatic hydrolysis of cellulosic biomass is often incomplete. Understanding the limitations of the process would aid in improving the process. Among the limitations of enzymatic hydrolysis, structural properties of cellulose have a large effect on enzymatic hydrolysis efficiency. The aim of this study was to increase the understanding of the relation between enzymatic hydrolysis and structural properties of cellulosic substrates. In the current work, different cellulosic substrates were imaged and structural changes of cellulosic substrates were characterized in real-time in micrometer scale with nonlinear optical microscope, employing multi-photon excitation fluorescence (MPEF), second-harmonic generation (SHG) and coherent anti-Stokes Raman scattering (CARS) modalities. Solid-state cross-polarization magic angle spinning carbon-13 nuclear magnetic resonance (CP/MAS 13C-NMR) was employed to quantify the spatial polymer distribution, accessible surface area, crystallinity and porosity in cellulosic substrates in nanometer scale. An array of cellulosic substrates was used in our study coming from softwood preparations used in pulp and paper industry and some model substrates. A strong correlation was found between the average pore size of the starting material and the enzymatic conversion yield. The degree of crystallinity was maintained during enzymatic hydrolysis of the cellulosic substrates. A substrate depended hydrolysis pattern was observed during enzymatic hydrolysis in real-time.