Biofabrication and Physicochemical Characterization of Bioplastic Films from Ipomoea batatas and Solanum tuberosum Peels

Abstract

Plastic pollution remains a critical global environmental concern, making the search for alternative and eco-friendly materials increasingly important. This study investigated the synthesis of biodegradable bioplastic films using starch extracted from sweet potato and Irish potato peels, an agro-waste resource. Starch was extracted from both peel types and used to produce bioplastic films through gelatinisation with glycerol and acetic acid as plasticisers. The resulting films were subjected to solubility, swelling behaviour, biodegradability, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) analyses. Sweet potato peels yielded more starch (5.60%) than Irish potato peels (4.80%). The sweet potato-based bioplastic had the highest swelling capacity in water (1.01 g), indicating high hydrophilicity. The blended sweet potato-Irish potato bioplastic film showed minimal swelling in methanol (0.20 g) and the lowest swelling in chloroform (0.12 g). All synthesised bioplastic films were soluble only in sulphuric acid and were insoluble in ammonia, acetic acid, acetone, and isopropyl alcohol, whereas the commercial plastic was partially soluble in ammonia. After 8 days, the blended peel bioplastic film showed greater degradation in loamy soil (53.84%) than in sandy soil (13.31%), followed by the Irish potato-based film (49.32% and 5.26%, respectively) and the sweet potato peel-based film (17.19% and 2.10%, respectively). FTIR spectra confirmed characteristic peaks of starch-based polymers, including broad -OH bands (~3352 cm⁻¹ and 3400 cm⁻¹), C=O stretching bands (1734.06 and 1793.85 cm⁻¹), and strong C-O and C-O-C stretching bands in the fingerprint region (900-1200 cm⁻¹). SEM revealed irregular structures in the bioplastic films. EDX analysis identified carbon (55.96%, 53.87%, and 62.53%), nitrogen (24.53%, 18.78%, and 14.57%), and sodium (13.90%, 12.90%, and 0.22%) as the dominant elements in the sweet potato, Irish potato, and blended peel bioplastic films, respectively. These findings support the valorisation of agricultural waste into eco-friendly bioplastics and indicate that sweet potato and Irish potato peels may serve as raw materials for bioplastic-film production.