Photosynthetic Synergism for Sustained Power Production with Microalgae and Photobacteria in a Biophotovoltaic Cell

This article documents the synergetic interaction between oxygenic photosynthesis (microalgae; cathode) and anoxygenic photosynthesis (photosynthetic bacteria; anode) toward bioenergy and biomass generation apart from wastewater treatment using a dual chambered biophotovoltaic cell. Microalgae as the biocathode negate the requirement of an external terminal electron acceptor as they can be efficient in situ oxygenators that facilitate the oxygen reduction reactions. Experiments were performed in a fed batch mode using designed synthetic wastewater at variable organic loading rates in the anodic chamber and domestic sewage as feed in the cathodic chamber with a retention time of 72 h. Operation at OL3 (1500 mg/L) showed maximum power output (0.7 V; 103 mW/m(2)). Anodic chamber showed a maximum substrate (COD) degradation efficiency of 81%, while the cathode showed a constant COD removal efficiency of 90%. Maximum microalgal lipid productivity of 20% was observed at OL4 and OL5. The designed biophotovoltaic cell provided a synergistic interaction between photosynthetic bacteria (anoxygenic photosynthesis) and microalgae (oxygenic photosynthesis) which facilitated multiple benefits viz., bioelectricity generation, biofuel production, CO2 sequestration and wastewater treatment along with in situ generation of oxygen as terminal electron acceptor.