BACKGROUND Microalgae have attracted worldwide interest resulting from their extensive applications in renewable energy and biomass production. However, in algal fuel cells, photosynthetically evolved oxygen hinders the use of algal biofilms formed at the anode surface. Here, nanostructured bio-electrochemical systems have been designed to explore the algal bio-electrochemistry at different illumination and growth conditions. RESULTS Three algal strains were screened for their exoelectrogenic activity and the possibility of direct electron transfer to the chemically modified surfaces. After adjusting light and dark conditions and medium compositions, oxygen production within the fuel cells was regulated. At the anode surface, the obtained bioelectrochemical responses and the morphological characterizations suggested that Oscillatoria agardhii has the potential to serve as electron donor and the nanostructured surface is the final electron acceptor. To that end, dual-chamber algal fuel cells were constructed and glucose (10 g L-1) was used as carbon source. CONCLUSION Power density of 26.8 mW m(-2) was produced using the biofilm formed by O. agardhii. Eventually, the consumption of organic waste was monitored, whereas the chemical oxygen demand removal reached 82%. (c) 2019 Society of Chemical Industry