In-situ biogenic FeS boosted acetate accumulation through CO2 capture and valorization using microbial electrosynthesis (MES)

Biosynthetic strategy of ferrous sulfide (FeS) through Shewanella oneidensis MR-1 in bioelectrochemical systems has been extensively explored to maintain bettered electron transfer performance. In this study, the simultaneous FeS biosynthesis and CO2 reduction were conducted in the microbial electrosynthesis (MES) system, aiming at improving electron transfer efficiency as well as acetate production. It was shown that the FeS was successfully biomineralized and then loaded onto the sludge in the Fe3+/S2O32−/MR-1 group, of which the acetate accumulation increased by 87.50%, 64.63% and 33.66% than the control, MR-1 and Fe3+/S2O32− groups. Also, electrochemical performance revealed by the CV analysis was enhanced, whereas the increased EPS accumulation and intracellular electron transfer activity by the biosynthesized FeS could also be proved. Moreover, the biogenic FeS enriched the abundances of acetogenic and sulfur-utilizing species as Acetobacterium, Clostridium_sensu_stricto_13, Sulfuricurvum and Desulfovibrio. Meanwhile, strongly positive correlations between Shewanella, the sulfur utilizers and acetogens were confirmed in the Fe3+/S2O32−/MR-1 group. With improved electron transfer efficiency and the boosted acetate accumulation, the in-situ biogenic FeS might be promising for CO2 capture and utilization.