16-01: Crystallinity – a key parameter for cellulosic biomass hydrolysis

Our overall research goal is to understand connections between accessibility, hydrolyzability, and reactivity for the prediction of hydrolysis rates in the pretreatment of cellulosic and lignocellulosic substrates.  To do this, we have been quantifying the connections between crystallinity, equilibrium adsorption, and reaction rate for these substrates. For example, steam explosion is one of the most effective pretreatment methods in disrupting lignocellulosics structure and enhancing its accessibility. The key operational parameters including temperature, residence time, and acid concentration have pronounced effects on crystallinity index (CrI) of the feedstock. The CrI of pretreated lignocellulosic biomass was calculated from X-ray diffractometry with the method of Least-squares and was found to decrease as pretreatment severity increases. Furthermore, the CrI of cellulose fraction in the steam-pretreated substrate is found to decrease proportionally with cellulose conversion. A series of steam-exploded lignocellulosic samples with varying CrI was generated and the significance of CrI is confirmed by a linear relationship between initial hydrolysis rates and CrI. To more fully explore the connection we have also undertaken experiments with phosphoric acid swollen Avicel^® at different levels of conversion. We will present the quantitative trends between the rate of conversion and these underlying substrate properties. The present studies provide evidence that the CrI is a key parameter determining the enzymatic hydrolysis rate of cellulosic biomass.