Nanocellulose Production in Future Biorefineries: An Integrated Approach Using Tailor-Made Enzymes

The development of process engineering approaches to integrate the production of biofuels and high value-added biobased products, such as enzymes and nanocellulose, is crucial to improve the financial performance and sustainability of lignocellulosic biomass biorefineries. Here, the feasibility of applying enzymes produced on-site to obtain nanocellulose was evaluated using eucalyptus cellulose pulp as a model feedstock. A systematic analysis of the structural properties of the nanomaterials obtained after hydrolysis using a cellulolytic enzymatic complex with high endoglucanase specific activity (17.09 IU/mg protein ), produced by Aspergillus niger, followed by sonication, revealed that longer ball milling pretreatment and reaction times favored extraction of the cellulose nanocrystals (CNCs). The highest yield (24.6%) of CNCs was achieved using 96 h of enzymatic hydrolysis of the ball-milled cellulose pulp, followed by sonication for 5 min. The CNCs presented approximate lengths of 294.0 nm and diameters of 24.0 nm, and the crystallinity index increased from 57.5% to 78.3%, compared to the cellulose pulp that was only ball milled. These findings demonstrated that nanocelluloses could be successfully extracted using on-site produced enzymes and that the sustainable integrated process reported here could contribute to the development of the nascent biobased economy.