Exploring the use of invasive algae Rugulopteryx okamurae and Gelidium corneum holocellulosic residue as additives in starch-based to develop sustainable materials

ABSTRACT The valorisation of marine biomass is increasingly considered a potential sustainable strategy for developing biodegradable packaging materials. In this work, the incorporation of Gelidium corneum holocellulosic residue and Rugulopteryx okamurae algae into starch-based films was explored to gain insight into their possible effects on film properties. Both marine biomasses appeared to contribute to improved moisture resistance, showing reductions in water intake, permeability and solubility, although the extent of these effects varied. Films containing Gelidium corneum generally showed more notable enhancements, including increased rigidity, with tensile strength at break values reaching up to roughly twice those of pure starch films. In contrast, the incorporation of Rugulopteryx okamurae tended to produce more heterogeneous films with lower mechanically performance, without clear improvements in tensile strength and in some reductions at higher algae concentrations. These differences may be related to variations in cellulose content and the degree of compatibility with the starch matrix. Thermal and XRD analyses indicated that starch retrogradation occurred during storage, leading to increases in crystallinity, an effect that appeared particularly marked in films with Rugulopteryx okamurae (from 13.4% to 58.3%). Biodegradation tests showed that only films containing Gelidium corneum films met the ISO 20200 standard of over 90% degradation within 90 days under composting conditions. Overall, Gelidium corneum residue and Rugulopteryx okamurae algae show potential as additives for producing starch-based films, although their influence on mechanical, thermal and water-related properties differs considerably.