Functional xanthan gum-based ZnO nanocomposite for antimicrobial applications: synthesis, properties, and performance...

The emergence of antibiotic-resistant microbes requires the development of superior antimicrobial materials. This study focuses on the chemical modification of xanthan gum (XG) by free-radical graft copolymerization with butyl acrylate (BuA) initiated by potassium persulfate (KPS), to significantly improve its structural, thermal, and functional characteristics. The relationship between reaction parameters and grafting performance was comprehensively analyzed, focusing on grafting yield (G), homopolymer formation (H%), and grafting efficiency (GE). Optimal grafting conditions (0.6 M BuA, 8 × 10^-2 M KPS, 60 °C, and 120 min) produced a graft copolymer with up to a 500% grafting yield. Zinc oxide nanoparticles (ZnO NPs) were manufactured in situ and integrated into the grafted copolymer matrix, resulting in the formation of the xanthan gum grafted by butyl acrylate with zinc oxide (XG-g-BuA/ZnO) nanocomposite. The structural, thermal, morphological, and crystalline properties were investigated utilizing FTIR, TGA, SEM/EDX/mapping, TEM, and XRD to validate successful grafting and incorporation of ZnO nanoparticles into the copolymer matrix. Thermal studies showed that the grafted XG displayed improved thermal stability compared to its unmodified counterpart, with thermal resistance increasing with increasing BuA content. The antibacterial efficacy was evaluated against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae), demonstrating substantial inhibitory effects, with the nanocomposite attaining up to 87.6%, 42.9%, 85.7% and 72.6% reduction in bacterial growth against Staphylococcus aureus, Bacillus subtilis, Escherichia coli and Klebsiella pneumoniae, respectively. These outcomes highlight the potential of the fabricated biopolymer nanocomposite as a sustainable and efficient platform for antimicrobial applications in both packaging and biomedical fields.