Low-fibrillated bacterial cellulose nanofibers as a sustainable additive to enhance recycled paper quality.

Bacterial cellulose is a biological macromolecule synthesized by bacteria of high purity and crystallinity. Bacterial cellulose nanofibers (BCNF) have been produced by soft homogenization and added to a recycled pulp to improve its quality. The benefits of BCNF on mechanical, physical and optical paper properties have been quantified and the retention mechanism of the BCNF in the paper network has been proposed. The use of BC to improve paper strength is usually limited by the decrease of tear index. The novelty of this work is that these two effects are decoupled by the addition of BCNF of low fibrillation (35.2%). In this way, some BCNF clusters are produced together with the individual nanofibers. Thus, with the addition of 3% BCNF, tensile and tear indexes as well as strain at break were improved by 11.1, 7.6, and 66.8%, respectively. Furthermore, the clusters were retained in the fiber network not only by hydrogen bonding, but also by physical retention within the gaps. Therefore, the addition of BCNF not only increases the mechanical properties of paper but also makes the handsheets more flexible and facilitates filler retention.