Fabrication of sisal fiber-derived beads from sustainable solvents: investigating their potential for pH-responsive sorption of bovine serum albumin

Abstract Gel beads were prepared from sisal fibers (SFs) by dissolving the treated biomass in green solvent systems (NaOH–urea and ZnCl 2 aqueous solutions), followed by regeneration in different coagulation media (HNO 3 , CaCl 2 , and ethanol). This sustainable strategy converts renewable sisal biomass into functional bio-based materials that serve as promising alternatives to fossil-derived polymers. The effects of dissolution and regeneration conditions on the physicochemical and structural properties of the resulting gel beads were systematically investigated. Distinct morphological, porosity, and swelling behaviors were observed depending on the processing method. Beads prepared using the NaOH–urea system showed compact, uniform pore structures with less swelling at higher SF content, whereas ZnCl 2 -activated beads displayed adjustable porosity and swelling influenced by the regeneration medium. Ethanol-coagulated beads exhibited an open pore network with the highest porosity (57%), large pore size (36.5 µm), and excellent swelling capacity (4144%). These beads were further tested for protein adsorption using bovine serum albumin (BSA) as a model, showing superior sorption capacity for ZnCl 2 –ethanol beads (107.9 mg g −1 at pH 3.0). Overall, the results demonstrate that processing conditions play a key role in controlling the structure–property relationships of lignocellulosic sisal fiber-derived beads and govern their performance in protein sorption, highlighting the versatility of this approach for designing high-performance, sustainable biomaterials.