Dieter Rahmadiawan, Akmal, Hairul Abral, Stivan Kharisma Mukti, Dian Handayani, Upik Tadzkia Khairani, Dilla Ghania Putri, Shih-Chen Shi, S.M. Sapuan, R.A. Ilyas, Thiago F Santos
The valorization of agricultural biomass residues into high-value bio-based products plays a strategic role in advancing the bio-circular economy and strengthening climate and material resilience in Southeast Asia. In this study, polyphenol-rich Uncaria gambir leaf residues and surplus sago starch, both abundant and underutilized regional biomass resources, were converted into functional polyvinyl alcohol (PVA)-based biofilms through a scalable and low-energy solution-casting process. While PVA films incorporating gambir extract exhibit strong UV-shielding and antioxidant functionality, excessive hydrogen bonding was found to induce brittleness and rigidity. To address this limitation, sago starch residues were introduced as a biodegradable co-matrix to reduce crystallinity, and glycerol was incorporated as a natural plasticizer to restore flexibility and chain mobility. The resulting PVA/sago starch/gambir biofilms were systematically evaluated in terms of structural, mechanical, thermal, barrier, and antimicrobial properties. At 2% gambir loading, the films achieved a 72.4% reduction in UV transmittance. Mechanical performance improved, with a 12.6% increase in tensile strength and a 9.3% enhancement in elongation at break. FTIR and XRD analyses confirmed enhanced intermolecular hydrogen bonding, supported by FESEM observations revealing a denser and more homogeneous microstructure. Although no inhibition zones were observed in agar diffusion assays, suppressed bacterial colonization on film surfaces indicated bacteriostatic behavior. Overall, this work demonstrates a practical biomass conversion pathway for transforming regionally abundant agricultural residues into functional, low-carbon bio-based materials. The proposed approach supports the development of sustainable bio-products from local feedstocks and contributes to emerging bio-based industries in Southeast Asia. © 2026 Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
Department of Mechanical Engineering, National Cheng Kung University (NCKU), Tainan, 70101, Taiwan; Department of Mechanical Engineering, Universitas Negeri Padang, Sumatera Barat, Padang, 25173, Indonesia; Laboratory of Nanoscience and Technology, Department of Mechanical Engineering, Andalas University, Sumatera Barat, Padang, 25163, Indonesia; Laboratory of Sumatran Biota, Faculty of Pharmacy Andalas University, Sumatera Barat, Padang, 25163, Indonesia; Advanced Engineering Materials and Composites Research Centre, Department of Mechanical and Manufacturing Engineering, Universiti Putra Malaysia, UPM, Selangor, Serdang, 43400, Malaysia; Technology Center, Federal University of Rio Grande do Norte, Av. Prof. Sen. Salgado Filho, 3000, Rio Grande do Norte, Natal, 59072-970, Brazil
