Microplastics in the Anthropocene: Transitioning from conventional filtration to engineered microalgal remediation

Microplastic pollution has emerged as a critical global environmental challenge, as conventional wastewater treatment systems remain inefficient in removing micron- and nano-scale plastic particles. Existing physicochemical remediation technologies, including membrane filtration and chemical coagulation, often require high energy inputs and generate secondary waste streams, highlighting the need for sustainable and circular alternatives. This review critically examines the evolution of microplastic remediation strategies, emphasizing the transition from passive biological adsorption toward engineered, multifunctional remediation platforms based on microalgae. Initially, the mechanisms underlying natural phycoremediation are evaluated, including extracellular polymeric substance (EPS) mediated bio-adsorption, physical entrapment by filamentous algae, enzymatic biodeterioration, and photo-oxidative degradation driven by extracellular organic matter. Although wild-type microalgae demonstrate the ability to interact with microplastics, their performance is constrained by slow kinetics, species-specific variability, metabolic stress, and sensitivity to environmental conditions and toxic plastic additives. These limitations restrict their applicability in high-throughput industrial wastewater systems. Consequently, recent advances in synthetic biology have enabled a paradigm shift through engineered algal platforms such as RUMBA (Remediation and Upcycling of Microplastics By Algae). By redirecting cellular metabolism in Synechococcus elongatus to produce surface-localized limonene, engineered hydrophobic cyanobacterial cells achieve rapid and efficient microplastic capture (≈91.4% removal within 1 h), overcoming electrostatic repulsion barriers that limit passive aggregation. Beyond remediation, the captured biomass–plastic aggregates can be directly valorised into polymer composites, enhancing material toughness and ductility, thereby establishing a “remediation-as-production” framework aligned with circular bioeconomy principles. To address the complexity of environmental matrices, complementary hybrid approaches including dielectrophoresis for nanoplastic removal and natural coagulant systems for chemically aggressive effluents are also assessed. Techno-economic and life-cycle analyses indicate that integrating algal remediation with nutrient recovery, wastewater treatment, and bioplastic manufacturing can achieve carbon-negative outcomes. This review demonstrates that coupling synthetic biology, materials engineering, and hybrid treatment technologies provides a scalable pathway to transform microplastic pollution from an environmental burden into a resource opportunity.