Isolation and utilization of cellulosic elements from the plant cell wall

Abstract

Two very different types of cellulosic materials that may be isolated from plant-based sources are here reviewed. We have shown that long helical cellulosic coils may be isolated by gentle chemical treatment of leaf petioles. The coils stem from protoxylem elements and are readily distinguished from other cellulosic components by polarized light microscopy, forming single- or multi-stranded left-handed helices. More widely known are the nanometer thickness cellulosic elements that may also be isolated from plant cell walls. These â nanocellulosesâ can be subdivided into two main families. Cellulose nanocrystals (CNC) are less than 250 nm long and are usually made by sulfuric acid hydrolysis. CNC form stable liquid crystalline suspensions in water that dry to give iridescent coloured films, analogous to those found in some tropical plants. Cellulose nanofibrils (CNF) are much longer, and may have carboxyl groups on the surface. Both CNC and CNF are intrinsically hydrophilic, and form useful aqueous gels and viscosity modifiers. By altering the surface chemistry, the nanocelluloses can also be incorporated as strengthening agents in composite materials. A wide range of commercial applications for these renewable materials has been proposed.