Preparation and characterization of cellulose nanowhiskers from cotton fibres by controlled microbial hydrolysis

The cellulolytic fungus Trichoderma reesei was used to prepare cellulose nanowhiskers (CNW) by controlled hydrolysis of microcrystalline cellulose (MCC). The penetration of fungus into the ordered regions of MCC resulted in reduction (10%) of its crystallinity. The zeta potential of fungal hydrolyzed CNW was similar to that of native MCC while that of CNW prepared by acid hydrolysis was five times higher due to its surface sulfation. Also, fungal hydrolyzed CNW resulted in monodomain structure under polarized light microscopy (PLM) while it was polydomain for that of acid hydrolyzed CNW. Atomic force microscopic (AFM) analysis confirmed the preferential orientation (anisotropy) of CNW on drying. Preparation of CNW by concentrated sulfuric acid hydrolysis process is energy intensive, environmentally hazardous and the surface of CNW is chemically modified (sulfated). But fungal hydrolysis resulted in CNW without any surface modification and such nanostructures show promise for applications in eco-friendly composites and pharmaceuticals.