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Lignocellulose nanofibrils (LCNFs) are nano-objects that contain lignin. The presence of lignin in the fibrils affects the process production of cellulose nanofibrils. It modifies the morphology of fibrils produced and the rheological behavior of suspensions, which is crucial in developing applications for this material. This work aims to understand the role of lignin in the mechanical-enzymatic production process of LCNFs and the morphological, superficial, and rheological properties of LCNF suspensions. Lignin has a negative effect on the mechanical and enzymatic processes, generating larger fibrils with less homogeneous size distributions and with lower zeta potential. In addition, the composition of the fibrils changes, part of the lignin is removed and dispersed into the solvent in the form of lignin nanoparticles. These nanoparticles are neutral and can be deposited on the surface of the fibrils. Regarding rheological properties, fibrils with lignin are less flexible than bleached fibrils. Such characteristics are due to the cementing capacity of lignin, which increases the hydrodynamic volume that these structures occupy per unit mass. Furthermore, in the semi-dilute region, lignin acts as a control agent for the viscosity in the suspensions due to its hydrophobic characteristic, which forms weak aggregates, poorly hydrated, and hydrodynamically smaller, which generate less resistance to flow. [ABSTRACT FROM AUTHOR]

Cellulose nanofibril (CNF) films have attracted great attention in food packaging application due to their excellent mechanical strength and oxygen barrier properties. If antibacterial nanoparticles are incorporated into CNF films, the generated antibacterial CNF films would further improve their packaging performance. Since the commonly used inorganic nanoparticles would persist in the environment after usage, biopolymer-based nanoparticles are highly desirable. Herein, novel antibacterial lignin nanoparticles were designed by the nanoprecipitation of the tetrahydrofuran (THF) solution of lignin into the aqueous solution of polyhexamethylene guanidine hydrochloride (PHGH). The as-fabricated spherical PHGH-LNPs had an average diameter of 135 ± 2 nm and zeta potential of approximately 50 mV with an excellent pH (4–10) and time stability (even after storage for 90 days). Due to the positive charge of PHGH-LNPs and the hydrophilic character of PHGH, the nanoparticles displayed a good dispersion in the CNF slurry. PHGH-LNPs/CNF films were obtained by further solvent casting. The excellent compatibility between PHGH-LNPs and CNFs leaded to the composite film with a similar tensile strength and unapparent fibril structure in comparison with that of the pristine CNF film. In particular, the PHGH-LNPs/CNF film at a nanoparticle dosage of 8 wt% presented a water vapor barrier ratio of 34% and 100% inhibition against both L. monocytogenes and E. coli. [ABSTRACT FROM AUTHOR]