Multifunctionalized Immobilized Microalgae Technologies for Application in Advanced Environmental Remediation Systems

Immobilized microalgae technologies (IMTs) involve the fixing of free-living microalgae onto specialized carriers through physical adsorption, chemical cross-linking, or biological interactions to enhance cell retention, metabolic stability, and stress resistance. These have emerged as multifunctional and sustainable platforms for environmental remediation, extending their applications beyond wastewater treatment to include soil and air purification. This review categorizes advanced IMT carriers into three major types: (1) inorganic engineered materials (e.g., biochar–nanoparticle hybrids), (2) functionalized organic polymers (e.g., pH-responsive hydrogels), and (3) bio-derived scaffolds (e.g., fungal–algal and algal–bacterial consortia). They enhance microalgal retention, metabolic activity, and microalgal stress resistance, enabling the effective removal of nitrogen, phosphorus, heavy metals, organic pollutants, and airborne particulates across diverse environmental matrices. We highlight key cooperative mechanisms—such as extracellular polymeric substance (EPS)-mediated adhesion, quorum sensing, and metabolic synergy—that underpin pollutant removal and biomass stability. Particular emphasis is placed on integrating smart technologies, including magnetic microrobots, 3D/4D-printed scaffolds, and AI-guided optimization, which improve the scalability, adaptability, and environmental responsiveness of IMT systems. By synthesizing the advances in materials science, microbial ecology, and environmental engineering, this review defines the future direction of research into IMTs as a next-generation bioengineering strategy for the integrated management of water, soil, and air pollution.