Local morphological and dimensional changes of enzyme-degraded cellulose materials measured by atomic force microscopy

A study of the degradation effects of enzyme treatment on the dimensional changes of cellulose aggregate fibrils (CAFs) with dimensions of ~100,000 x 3,000 x 300 nm from fully bleached kraft fiber was performed. CAFs were incubated with cellulase for up to 32 h. The insoluble CAFs fragments remaining after enzymatic hydrolysis were then subjected to variable relative humidity (RH). Each sample was imaged by an atomic force microscope (AFM) in tapping mode. The images were analyzed to determine the dimensional changes of the insoluble CAFs. Enzymatic hydrolysis continuously depolymerized the CAFs over 32 h, ultimately causing 20% of the CAFs to become soluble. Compared to initial dimensions of the reference CAFs with no enzymatic treatment, the dimensions of the enzyme treated CAFs were generally more responsive to humidity and exhibited an increased frequency of plastic deformations.