Enzyme-Modulated Anaerobic Encapsulation of Chlorella Cells Allows Switching from O₂ to H₂ Production

Single-cell encapsulation has become an effective strategy in cell surface engineering; however, the construction of cell wall-like layers that allow the switching of the inherent functionality of the engineered cell is still rare. In this study, we show a universal way to create an enzyme-modulated oxygen-consuming sandwich-like layer by using polydopamine, laccase, and tannic acid as building blocks, which then could generate an anaerobic microenvironment around the cell. This layer protected the encapsulated C. pyrenoidosa cell against external stresses and enabled it to switch from normal photosynthetic O₂ production to photobiological H₂ production. The layer showed an smaller effect on the PSII activity, which contributed a significant enhancement on the rate (0.32 μmol H₂  h^-1  (mg chlorophyll)^-1 ) and the duration (7 d) of H₂ production. This strategy is expected to provide a pathway for modulating the functionality of cells and for breakthroughs in the development of green energy alternatives.