In-Cell Engineering of Protein Crystals into Hybrid Solid Catalysts for Artificial Photosynthesis

The emergence of protein-based crystalline materials offers promising opportunities in enzyme immobilization. However, the current systems used for encapsulation of protein crystals are limited to either exogenous small molecules or monomeric proteins. In this work, polyhedra crystals were used to simultaneously encapsulate the foreign enzymes FDH and the organic photocatalyst eosin Y. These hybrid protein crystals are prepared easily by cocrystallization within a cell without a requirement for complex purification processes because they spontaneously form 1 μm scale solid particles. After immobilization within protein crystals, the recombinant FDH is recyclable and thermally stable and maintains 94.4% activity compared to the free enzyme. In addition, the incorporation of eosin Y endows the solid catalyst with CO₂-formate conversion activity based on a cascade reaction. This work indicates that engineering protein crystals by both in vivo and in vitro strategies will provide robust and environmentally friendly solid catalysts for artificial photosynthesis.