Impact of bioelectricity on DNRA process and microbial community composition within cathodic biofilms in dual-chambered bioelectrode microbial fuel cell (MFC).

The synchronous bioelectricity generation and dissimilatory nitrate reduction to ammonium (DNRA) pathway in Klebsiella variicola C1 was investigated. The presence of bioelectricity facilitated cell growth on the anodic biofilms, consequently enhancing the nitrate removal efficiency decreasing total nitrogen levels and causing a negligible accumulation of NO2- in the supernatant. Genomic analysis revealed that K. variicola C1 possessed a complete DNRA pathway and largely annotated electron shuttles. The up-regulated expression of genes narG and nirB, encoding nitrite oxidoreductase and nitrite reductase respectively, was closely associated with increased extracellular electron transfer (EET). High-throughput sequencing analysis was employed to investigate the impact of bioelectricity on microbial community composition within cathodic biofilms. Results indicated that Halomonas, Marinobacter and Prolixibacteraceae were enriched at the cathode electrodes. In conclusion, the integration of a DNRA strain with MFC facilitated the efficient removal of wastewater containing high concentrations of NO3- and enabled the environmentally friendly recovery of NH4+.

Bioelectricity facilitates carbon dioxide fixation by Alcaligenes faecalis ZS-1 in a biocathodic microbial fuel cell (MFC).

The CO2 fixation mechanism by Alcaligenes faecalis ZS-1 in a biocathode microbial fuel cell (MFC) was investigated. The closed-circuit MFC (CM) exhibited a significantly higher CO2 fixation rate (10.7%) compared to the open-circuit MFC (OC) (2.0%), indicating that bioelectricity enhances CO2 capture efficiency. During the inward extracellular electron transfer (EET) process, riboflavin concentration increased in the supernatant while cytochrome levels decreased. Genome sequencing revealed diverse metabolic pathways for CO2 fixation in strain ZS-1, with potential dominance of rTCA and C4 pathways under electrotrophic conditions as evidenced by significant upregulation of the ppc gene. Differential metabolite analysis using LC-MS demonstrated that CM promoted upregulation of various lipid metabolites. These findings collectively highlight that ZS-1 simultaneously generated electricity and fixed CO2 and that the ppc associated with bioelectricity played a critical role in CO2 capture. In conclusion, bioelectricity resulted in a significant enhancement in the efficiency of CO2 fixation and lipid production.

Effective Visible Light-Driven Photocatalytic Degradation of Ciprofloxacin over Flower-like Fe3O4/Bi2WO6 Composites.

Photocatalytic degradation of organic pollution is a vital path to deal with environmental problems. Here, a direct Z-scheme 2D/2D heterojunction of a Fe3O4/Bi2WO6 photocatalyst is fabricated for the degradation of ciprofloxacin by a self-assembly strategy. Furthermore, to characterize the morphology of the obtained composite photocatalysts, various kinds of characterization methods were employed like XRD, XPS, SEM, and TEM. It is indicated that the flower-like photocatalyst is composed of nanosheets. Comparable photocatalysts were prepared by controlling the hydrothermal temperature and the iron content. In the photocatalytic degradation of ciprofloxacin (CIP) in water, under visible light irradiation, FB-180 (synthesized at 180 °C with 4% iron content) presents approximately 99.7% degradation efficiency in only 15 min. Meanwhile, during photocatalytic degradation reactions, the Fe3O4/Bi2WO6 heterojunction also displayed excellent stability, which still kept above 90% degradation efficiency after five consecutive cycles. UV-Vis DRS and M-S analyses showed that the Fe3O4/Bi2WO6 catalyst has a strong visible light absorption capacity and the transfer pathway of photo-induced charge carriers. PL, EIS, and TPR showed that Fe3O4/Bi2WO6 has an efficient separation and transfer rate of the photo-generated carriers. ESR analysis proved that the superoxide radical (•O2 -) and hydroxyl radical (•OH) play a major role in the Fe3O4/Bi2WO6 photocatalytic system. This special 2D/2D heterojunction we proposed may have huge potential for marine pollution treatment by photocatalysis degradation with dramatically boosted activities.