Sustainable valorization of Agave durangensis leaves into microcrystalline cellulose for reinforcing sodium alginate films: A circular bioeconomy perspective for the mezcal industry.

The mezcal industry generates substantial amounts of lignocellulosic (LC) waste from agaves, which remain underutilized despite containing valuable cellulose, hemicellulose, and lignin. Cellulose, the most abundant polysaccharide on Earth, offers great potential for sustainable material development. In the food packaging sector, biopolymer-based films are biodegradable alternatives often presenting lower performance than synthetic polymers, a limitation that can be addressed by incorporating reinforcing agents such as microcrystalline cellulose (MCC). This work demonstrates that Agave durangensis leaves are a valuable source of MCC capable of reinforcing sodium alginate (SA) films for potential packaging applications, showing that mezcal residues can be valorized into functional biopolymers within a circular bioeconomy perspective. This study evaluated the incorporation of 1, 5 and 10 wt% MCC, obtained from discarded Agave durangensis leaves, into SA-based films plasticized with glycerol. MCC was obtained through sequential alkaline peroxide pulping without acid hydrolysis, yielding cellulose-rich fibers with characteristic FTIR signals, a crystallinity index (CrI) of 76.6 ± 0.9%, and a maximum degradation temperature (Tmax) of 334.9 °C. Control films showed smooth morphologies without cracks, presenting a tensile strength (TS), Young's modulus (YM), elongation at break (EAB), and Water Vapor Permeability (WVP) of 30.26 ± 1.28 MPa, 1575.43 ± 112.59 MPa, 2.45 ± 0.32%, and 60.6 ± 1.5 g mm/m2 day kPa, respectively. MCC incorporation modified the physicochemical properties of the films, resulting in rougher surfaces, cracks and aggregated fibers at higher concentrations. TS improved by 13.3% at 1 wt% MCC, while higher contents reduced TS, YM, and EAB. The WVP significantly increased in films containing 5 and 10 wt% MCC, while 1 wt% MCC decreased this property by 9.8%.