Agricultural residues are major potential resources for biomass and for material production. In this work, rice straw residues were used to isolate cellulose nanofibers of different degree of oxidation. Firstly, bleached rice fibers were produced from the rice straw residues following chemical extraction and bleaching processes. Oxidation of rice fibers mediated by radical 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) at pH 10 was then applied to extract rice cellulose nanofibers, with diameters of 3–11 nm from morphological analysis. The strengthening capacity of rice nanofibers was tested by casting nanocomposite films with poly(vinyl alcohol) polymer. The same formulations with eucalyptus nanofibers were produced as comparison. Their thermal and mechanical performance was evaluated using thermogravimetry, differential scanning calorimetry, dynamic mechanical analysis and tensile testing. The glass transition of nanocomposites was shifted to higher temperatures with respect to the pure polymer by the addition of rice cellulose nanofibers. Rice nanofibers also acted as a nucleating agent for the polymer matrix. More flexible eucalyptus nanofibers did not show these two phenomena on the matrix. Instead, both types of nanofibers gave similar stiffening (as Young’s modulus) to the matrix reinforced up to 5 wt.%. The ultimate tensile strength of nanocomposite films revealed significant enhancing capacity for rice nanofibers, although this effect was somehow higher for eucalyptus nanofibers.

In this study, avocado seed (AS) waste was used as a feedstock for bacterial cellulose (BC) production. Global avocado consumption continues to rise due to its recognised health benefits, resulting in substantial amounts of waste generated by the avocado processing industry. This work proposes the efficient utilisation of avocado seed residues—rich in fermentable sugars—to enhance the economic viability of BC production while supporting responsible agro-industrial waste management. Hydrolysed avocado seeds were incorporated into a modified Hestrin–Schramm (MHS) medium for BC production using Komagataeibacter xylinus as the bacterial strain. The BC membranes obtained from the modified medium (BC-MHS) exhibited higher production (1.93 g/L) and productivity (0.19 g/L·day) compared with those produced in the standard HS medium (BC-HS). The morphology and nanofibre diameter (11–85 nm) of the resulting BC were not significantly affected; however, BC-MHS showed higher crystallinity (~78%) and a higher degradation temperature (~357 °C) than BC-HS. Conversely, the modified medium slightly reduced the mechanical performance of the BC in terms of elongation at break, tensile strength, and Young’s modulus. Overall, avocado seed waste was successfully transformed into a value-added material, demonstrating its potential for agro-industrial waste valorisation through scalable and sustainable biorefinery processes.

Intelligent packaging represents a sustainable solution for food preservation by enabling the monitoring of freshness through chromatic changes. In this study, a biofilm based on polyvinyl alcohol (PVA), nanocellulose (NC) extracted from rice straw and blueberry extract was developed and evaluated for its performance as a visual freshness indicator in tilapia fillets. Nanocellulose, obtained by TEMPO oxidation, exhibited proper integration into the polymeric matrix according to transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray diffraction analysis. The biofilms improved their mechanical properties with the addition of NC, by increasing tensile strength and reducing water solubility. However, the incorporation of anthocyanins increased solubility and water vapor permeability due to their hydrophilic character. Despite this, their high chromatic sensitivity to pH allowed for color changes: red in acidic media (pH 2-4) and green/brown in alkaline media (pH > 9). These visual changes validate the potential of anthocyanins as freshness indicators, positioning biofilms as a functional and sustainable alternative to conventional packaging. In addition to enabling real-time monitoring, these biofilms can contribute to reducing food waste and fostering more sustainable solutions in the packaging industry, with significant potential for innovative commercial applications.