Prediction of Cellulose Crystallinity in Liquid Phase Using CBM-GFP Probe

Abstract

Carbohydrate-binding modules (CBMs) have been developed to investigate the presence of crystalline and amorphous regions of cellulose. However, systematic and quantitative assessment of cellulose crystallinity using such non-hydrolytic fusion proteins in liquid phase has not been reported. In this work, cellulose directed CBM probes containing a green fluorescent protein (GFP) were constructed and named CG17, CG28, and CG2a. The probe binding condition was determined as incubating 30 μg/mL probes in 10 mM phosphate buffer at 30 oC for 60 min. Under the optimized condition, the linear correlations between CBM probe binding capability and X-ray diffraction (XRD) crystallinity were well established. Using linear regression equations, the crystallinity of several cellulosic materials was well calculated. Amorphous component and cellulosic surface area probably had a less effect on binding capability of CG2a than that of CG17 and CG28. Therefore, crystalline-region specific probe CG2a should be an efficient tool for interpreting the crystallinity of cellulosic materials.