Algae-Bacteria cooperated microbial ecosystem: A self-circulating semiartificial photosynthetic purifying strategy

The microbial fuel cell (MFC) is a promising bio-electrochemical technology that enables simultaneous electricity generation and effluent purification. Harnessing solar energy to provide sustainable power for MFC operation holds great potential. In this study, a semiartificial photosynthetic self-circulating MFC ecosystem is successfully established through the collaboration of electrogenic microorganisms and photosynthetic algae. The ecosystem can operate continuously without carbon sources and produces a voltage of 150 mV under irradiation. The irradiation doubles the maximum power density of the ecosystem, reaching 8.07 W/m² compared to dark conditions. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) suggest a higher diffusion capacity or faster electron replenishment ability within the ecosystem. Furthermore, the capacity of ecosystem for removing chromium (Cr(VI)) has been investigated comprehensively. Under irradiation, the ecosystem demonstrates a 2.25-fold increase in Cr(VI) removal rate compared to dark conditions. Finally, the results of 16S rRNA amplicon sequencing indicates an increase in the relative abundance of strict and facultative aerobic electroactive bacteria in the ecosystem, including Citrobacter (21 %), Bacillus (15 %) and Enterococcus (6 %). The ecosystem offers a novel, self-sustaining approach to address the challenges of energy recovery and environmental pollution.