Enhanced Stability and Photochemical Activity of PhotosystemI from the Green Alga Chlamydomonas reinhardtii Upon Encapsulation in Organic Matrixes

Photosynthesis is a fundamental process that converts light energy into chemical energy, driven by photosystems. These chlorophyll-protein complexes enable a light-dependent electron transport chain, producing ATP and NADPH, which are essential for carbon fixation. Photosystem I (PSI), well-known for its greater photochemical performance and stability, has been utilized in hybrid nanodevices as a light converter and photocatalyst. However, membrane proteins, including PSI, often suffer from stability loss and decreased activity following purification due to their removal from the thylakoid membrane environment. To address these challenges, isolated PSI from Chlamydomonas reinhardtii was encapsulated into different biodegradable polymers, including poly lactic co-glycolic acid (PLGA), poly lactic acid (PLA), and chitosan (Ch), using double emulsion and ionic gelation methods, and stable PSI nanoparticles (100–500 nm) with tailored surface charges were produced. These matrices provide a stabilizing shell mimicking the natural environment, enhancing PSI stability and activity under different conditions of both temperature and pH. Herein, reported results demonstrate that encapsulated PSI maintains higher photochemical activity over time compared to detergent-stabilized PSI, with chitosan showing the highest efficiency in preserving PSI activity under strong light and extended periods. Remarkably, the encapsulated PSI retained activity up to 7–8 times greater over 28 days compared to the same complex stabilized in detergents. Finally, encapsulation offers enhanced stability and activity, leveraging the advantages of the microalgae in sustainable biomass production over land plants. This work paves way for environmentally friendly and efficient photocatalytic systems integrating photosynthetic components.