Structure–property relationships and intrinsic antibacterial potential of Saccharum spontaneum fibers toward sustainable biomaterial composites

Natural plant fibers are increasingly explored as sustainable reinforcements for next-generation composite materials. However, the correlation between their structural characteristics and intrinsic bio functional properties remains underexplored. This study systematically investigates Saccharum spontaneum stem fibers to establish structure–property–bioactivity relationships relevant to sustainable composite development. X-ray diffraction analysis confirmed a semi-crystalline cellulose I structure with a dominant (002) reflection at 2θ ≈ 21° and a crystallinity index of ~ 21%, indicating a predominantly amorphous lignocellulosic framework favorable for matrix interaction and surface functionalization. Fourier transform infrared spectroscopy revealed abundant hydroxyl and aromatic functional groups associated with cellulose, hemicellulose, and lignin, suggesting chemically active interfaces that may influence both mechanical bonding and antimicrobial interactions. Mechanical testing demonstrated a tensile strength of 52.17 MPa with a failure strain of 0.023, indicating suitability for non-structural and hybrid polymer composite systems. Thermogravimetric analysis revealed multi-stage degradation with primary polysaccharide decomposition between 300 and 430 °C and stable char formation temperature beyond 700 °C, confirming compatibility with thermoplastic processing such as PLA-based composites. Importantly, the lignocellulosic composition contributing to interfacial adhesion also imparted intrinsic antibacterial activity against Escherichia coli, producing inhibition zones of 28 ± 1 mm and 35 ± 1 mm at 50 µg and 100 µg, respectively. Confocal microscopy further confirmed antibiofilm disruption, linking chemical functionality to biological response. The findings demonstrate that the physicochemical architecture of Saccharum spontaneum fibers simultaneously governs mechanical reinforcement potential and intrinsic antibacterial behavior, supporting their integration into sustainable bio functional composite systems rather than representing independent application domains.