Protein Self-Assembly as a Design Principle for Enzyme Immobilisation in Biocatalysis

Enzyme immobilisation is essential for translating biocatalytic processes from the laboratory to industrial applications by improving enzyme stability, recovery, and reuse. It underpins sustainable processes in pharmaceuticals, biofuels, and food production, but conventional immobilisation strategies involve inherent trade-offs. Covalent attachment prevents enzyme leaching but may distort the active site, whereas physical adsorption better preserves enzyme conformation but allows enzyme leaching. Furthermore, carrier-based methods frequently encounter mass-transfer limitations and may require external cross-linkers, hindering broader industrial application. Recent advances in synthetic biology and materials science have accelerated the development of protein-based materials for biocatalysis. This review examines protein self-assembly as a unifying design principle for enzyme immobilisation, enabling programmable assembly under relatively mild conditions to overcome key limitations of conventional strategies. We discuss naturally derived structures such as bacterial microcompartments and engineered systems including virus-like particles, elastin-like polypeptides, and SpyTag/SpyCatcher, which support programmable enzyme organisation and enable compartmentalised multi-enzyme cascade reactions. Building on this, a major focus is placed on catalytically active inclusion bodies (CatIBs). As robust, intrinsically self-immobilised protein aggregates, CatIBs represent a simplified, carrier-free platform offering potential process and cost advantages for industrial biocatalysis.