Development and characterization of biodegradable films from xanthan gum/polyvinyl alcohol polymeric blends reinforced with cellulosic nanostructures for food packaging applications

Abstract

Biodegradable polymers are a class of materials that have emerged as an alternative to mitigate environmental issues caused by the use and improper disposal of petroleum-derived polymers. In this context, the development of new materials based on more efficient and sustainable technologies has intensified, aiming to replace synthetic plastics. However, the production of biodegradable materials still faces limitations, mainly due to high manufacturing costs and inferior thermo-mechanical and barrier properties against gases and moisture. A viable strategy to overcome these limitations is the use of polymer blends, which allow the tailoring of material properties to meet specific demands. This approach shows great potential for applications in various sectors, especially in the production of flexible packaging. In this context, the present study aimed to produce and characterize flexible films based on xanthan gum (XG) and polyvinyl alcohol (PVA), using the solvent evaporation method. Xanthan gum was produced in the laboratory via submerged fermentation from sugarcane bagasse, an agro-industrial residue, using the bacterium Xanthomonas campestris CCT5268. The resulting biopolymer yielded 2 g/L, exhibited pseudoplastic behavior (apparent viscosity of 135 mPa·s at 25 °C and 25 s⁻¹), a molar mass of 1,238,000 kDa, and thermal resistance up to 300 °C, values slightly superior to those of commercial gum. FTIR analyses revealed characteristic absorption bands of polysaccharides, indicating structural similarity between the samples. Polymeric blends developed with commercial XG and lab-produced gum (XGL) showed significant improvements compared to the PVA control film, such as reduced thickness and maintained thermal stability (200 °C for PVA/XG and 195 °C for PVA/XGL). The PVA/XGL1 blend stood out with a tensile strength of 34 MPa, elongation of 270.97%, water vapor permeability of 0.243 g·mm/m²·h·kPa, and a contact angle of 80.81°, indicating greater hydrophobicity and polymer compatibility. Subsequently, the films were enhanced by incorporating cellulose nanofibrils (CNF) into mono- and bilayer films, along with corona treatment applied to bilayer systems. CNF incorporation increased tensile strength to 46.57 MPa and improved thermal stability (348.6 °C) in monolayer films. In bilayer films without corona treatment, increased stiffness (Young’s modulus of 1679.64 MPa), tensile strength of 48.11 MPa, and a significant reduction in flexibility (elongation of 37.79%) were observed, indicating lower interfacial compatibility between layers. Solubility was 9.80%, and opacity increased, with 85% transmittance, features favorable for packaging light- and moisture-sensitive foods. In bilayer films with CNF and corona treatment, a significant improvement in flexibility (elongation of 158.88%), reduced solubility (8.10%), and increased opacity (transmittance of 78.05%) were observed. These modifications indicate enhanced interfacial adhesion and improved functional performance. The results obtained across the three studies demonstrate the technical feasibility of producing xanthan gum from agro-industrial residues and its application in advanced polymer systems. The combination of PVA and XG, reinforced with CNF and surface-modified via corona treatment, resulted in biodegradable films with functional properties suitable for sustainable packaging, contributing to waste valorization and reduced environmental impact.