Improvement of biotic nitrate reduction in constructed photoautotrophic biofilm-soil microbial fuel cells

• Published in: Journal of environmental management Vol. 360; p. 121066
• Main Authors: Cheng, Yu, Ding, Jue, Wan, Jiahui, Tang, Li, Joseph, Akaninyene, Usman, Muhammad, Zhu, Ningyuan, Zhang, Yanxia, Sun, Han, Rene, Eldon R., Lendvay, Marton, Li, Yiping
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.06.2024
• Subjects: Bioelectric Energy Sources; Biofilms; Carbon - metabolism; Carbon source; Electrodes; Electron donors; Microbial fuel cell; Nitrate reduction; Nitrates - metabolism; Oxidation-Reduction; Paddy soil; Soil - chemistry; Soil Microbiology; Microbial fuel cell; Carbon source; Electron donors; Nitrate reduction; Paddy soil
• ISSN: 0301-4797; 1095-8630
• DOI: 10.1016/j.jenvman.2024.121066

The biotic nitrate reduction rate in freshwater ecosystems is typically constrained by the scarcity of carbon sources. In this study, ‘two-chambers’ - ‘two-electrodes’ photoautotrophic biofilm-soil microbial fuel cells (P-SMFC) was developed to accelerate nitrate reduction by activating in situ electron donors that originated from the soil organic carbon (SOC). The nitrate reduction rate of P-SMFC (0.1341 d−1) improved by ∼ 1.6 times on the 28th day compared to the control photoautotrophic biofilm. The relative abundance of electroactive bacterium increased in the P-SMFC and this bacterium contributed to obtain electrons from SOC. Biochar amendment decreased the resistivity of P-SMFC, increased the electron transferring efficiency, and mitigated anodic acidification, which continuously facilitated the thriving of putative electroactive bacterium and promoted current generation. The results from physiological and ecological tests revealed that the cathodic photoautotrophic biofilm produced more extracellular protein, increased the relative abundance of Lachnospiraceae, Magnetospirillaceae, Pseudomonadaceae, and Sphingomonadaceae, and improved the activity of nitrate reductase and ATPase. Correspondingly, P-SMFC in the presence of biochar achieved the highest reaction rate constant for nitrate reduction (kobs) (0.2092 d−1) which was 2.4 times higher than the control photoautotrophic biofilm. This study provided a new strategy to vitalize in situ carbon sources in paddy soil for nitrate reduction by the construction of P-SMFC. [Display omitted] •Photic biofilm-soil microbial fuel cells (PSMFC) were tested for nitrate removal.•Electroactive bacteria activated the in situ electron donor pools in soil.•Denitrifiers of the photic biofilm thrived in PSMFC, in the presence of biochar.•The denitrifiers made the main contribution to nitrate reduction among all the species.