From Fishery Waste to Functional Adhesives: Milkfish (Chanos chanos) Skin Collagen–Polyvinylpyrrolidone Physically Crosslinked Biohybrid Adhesive for Sustainable Paper Bonding

Environmental concerns over plastic-based adhesives highlight the urgent need for biodegradable alternatives. This study transforms milkfish (Chanos chanos) skin waste from the fishery industry into a collagen–polyvinylpyrrolidone (PVP) biohybrid adhesive stick for paper bonding. Milkfish showed the highest adhesive strength among twenty species, requiring ≥213.7 mg/g hydroxyproline for optimal performance. Type I collagen was confirmed via Fourier transform infrared (FTIR) and amino acid composition, and the extraction yield reached 68.82%. The fish skin collagen–PVP glue stick demonstrated paper adhesion and physicochemical properties comparable to starch-based and commercial glues, with lower hardness and more dry adhesive per unit area. Sensory evaluation using quantitative descriptive analysis revealed no significant differences (p < 0.05) compared to commercial glue sticks, except for increased glue consumption and reduced shape retention. The shelf life exceeded 70 days. Collagen adhesive from fish skin offers comparable efficiency to chemical and other bio-based adhesives, providing a sustainable solution that promotes the circular economy and green innovation.