Production of High Solid Nanocellulose by Enzyme-Aided Fibrillation Coupled with Mild Mechanical Treatment

Abstract

Plant-based cellulosic materials are intriguing building blocks for functional materials, and sustainable nanocellulose production strategies have been intensively explored. Most of the existing strategies, however, suffer from the fact that highly energy-intensive fiber fibrillation yields a nanocellulose gel containing more than 95% water. We showcase a high throughput production method for nanocellulose, which primarily exploits the efficiency of enzymatic actions to disintegrate pulp fibers at a notable high solid content (25 wt %) without the need for high shear disintegration. The main enzyme activity exploited was cellobiohydrolase with the aid of endoglucanase. A pastelike fibril network is postulated to be formed through a peeling-type of reaction induced by the combined action of the enzymes used and fiber–fiber friction, with a yield of approximately 85%. Based on scanning electron microscopy and atomic force microscopy analyses, the formed nanocellulose can be classified as microfibrillated cellulose (i.e., cellulose microfibrils). Solid-state NMR and X-ray diffraction investigations revealed that the fibril morphology remained mostly intact. Our intriguing finding of a fraction with nanosized rodlike cellulose particles shows the power of enzymes in nanocellulose production. Our approach to producing nanocellulose at a high solid content in a much less energy-intensive manner puts forward the sustainable production of nanocellulose.