Photosystem I (PSI) is a pigment binding multisubunit protein complex involved in the light phase of photosynthesis, catalyzing a light-dependent electron transfer reaction from plastocyanin to ferredoxin. PSI is characterized by a photochemical efficiency close to one, suggesting its possible application in light-dependent redox reaction in an extracellular context. The stability of PSI complexes isolated from plant cells is however limited if not embedded in a protective environment. Here we show an innovative solution for exploiting the photochemical properties of PSI, by encapsulation of isolated PSI complexes in PLGA (poly lactic-co-glycolic acid) organic microparticles. These encapsulated PSI complexes were able to catalyze light-dependent redox reactions with electron acceptors and donors outside the PLGA microparticles. Moreover, PSI complexes encapsulated in PLGA microparticles were characterized by a higher photochemical activity and stability compared with PSI complexes in detergent solution, suggesting their possible application for ex vivo photocatalysis.