Bioelectricity and bioactive compound productionin an algal-assisted microbial fuel cell with immobilized bioanode

Abstract

This study investigates the influence of immobilized bacterial anode on the performance of algal-assisted microbial fuel cell (AAMFC) that treats dairy wastewater with concurrent bioelectricity and bioactive compound production. Immobilized exoelectrogenic bacterium—Enterobacter aerogenes—was used in the anode region, and Nostoc sp. was used in the cathode region. The investigation on the influence of sodium alginate (SA) concentration indicated that E. aerogenes immobilized using 20 g/L SA produced highest power density of 168 ± 3.5 mW/m2, whereas free cells showed 75 ± 5.32 mW/m2. The coulombic efficiency, chemical oxygen demand (COD) removal, and volatile fatty acid (VFA) recovery obtained for cells immobilized using 20 g/L SA were 12.54, 83.15, and 92%, respectively. This system gave a CO2 supply of 4.2 mM, which increased the productivity of Nostoc sp. to 64.3 ± 3.8 mg/L d. Algal cathode produced a maximum dissolved oxygen content of 12.8 mg/L. The constituents of Nostoc sp. were extracted using ethanol, and the antimicrobial activity of the extract was tested against aquatic bacterial pathogens. The extract at a dosage of 500 μg showed highest zone of inhibition of 11 mm for the gram-negative bacteria Citrobacter freundii and least inhibition of 2 mm for Escherichia coli. FTIR analysis of the extract confirmed the presence of bioactive compounds. This study substantiated that the immobilized anodic exoelectrogens with microalgal biocathode in an AAMFC will find a promising application in energy harvesting from wastewater and bioactive compound synthesis.