Microalgae-Derived Biopolymers: An Ecological Approach to Reducing Polylactic Acid Dependence

The growing demand for sustainable materials and the valorization of waste streams have intensified research on wastewater biorefineries and bioplastics. Within this framework, this study aims to develop and characterize poly (lactic acid) (PLA)-based films partially substituted with microalgae biomass derived from wastewater treatment at different concentrations (PLA-MA: 0, 10, 20, 30, 40, and 50%). The films were produced and systematically characterized in terms of their morphological (SEM), structural (FTIR), physical (thickness, weight, swelling, and solubility), thermal (TGA), mechanical (tensile strength, elongation at break, and Young’s modulus), optical (colorimetry and UV–Vis), barrier (water vapor permeability), and biodegradability properties. FTIR analysis confirmed the successful incorporation of microalgae biomass into the polymeric matrix and indicated good compatibility at low biomass loadings, whereas higher concentrations (>20%) introduced hydrophilic functional groups associated with increasing structural incompatibility. Partial substitution of PLA with microalgae biomass significantly modulated the physical, mechanical, and optical properties of the resulting composites. Notably, biodegradability assays revealed that the PLA-MA 50% composite achieved 89% degradation within 120 days, demonstrating that microalgal biomass markedly accelerates material decomposition. Furthermore, antimicrobial tests conducted for PLA-MA 0%, 20%, and 50% confirmed the safety of wastewater-derived microalgae for incorporation into the polymer matrix. Overall, these results highlight the potential of wastewater-derived microalgae biomass as a promising and sustainable component for short-life-cycle bioplastic applications, particularly in the agricultural sector.