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The coupling of microbial dissimilatory manganese (Mn) reduction and nitrogen transformation in anaerobic environment affects the fate of many elemental geochemical cycles. A strain of dissimilatory manganese reducing bacteria (DMRB) named Pantoea sp. MFG10 was isolated for simultaneous reduction of Mn(IV) oxides and NO 3 --N to explore the differential reduction mechanism. The post-reaction precipitates were investigated for researching potential persistent products. The strain MFG10 could achieve 99.86% NO 3 --N removal (1.176 mg L−1 h−1) and 20.97 mg L−1 (0.583 mg L−1 h−1) free Mn(II) yield within 12 and 36 h, respectively. The transient intermediate Mn(III) formed after the reduction of strain MFG10 was utilized in the denitrification process. The restricted Mn reduction behavior in the NO 3 --N and manganese oxide co-reduction system led to the formation of large amounts of Mn(III) by single electron transfer of Mn(IV). Mn(III) acts as electron donor and re-oxidized to constitute a dynamic manganese cycle pathway. Thus, the addition of manganese oxide significantly improved the denitrification efficiency and the fast electron flow formed an abundant Mn(III) secondary minerals on the surface of the manganese oxide. This work will help to understand the more subtle environmental and process-based manganese cycle and inspire new strategies to develop efficient manganese recycling processes for groundwater pollution control. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • The Mn redox cycle removed 94.67 % of E2 within 12 h (0.079 mg L−1h−1). • Interaction of reactive oxygen species and Mn(III) accelerated E2 removal. • Bioreactor showed 89.63% of NO 3 −-N and 97.57% of 17β-estradiol removal efficiency. • Community assembly enhanced the metabolic and physiological activity of bioreactor. • Different elemental cycles in the community were coupled with contaminant removal. The application of bio-manganese (Mn) redox cycling for continuous removal of contaminants provides promise for addressing coexisting contaminants in groundwater, however, the feasibility of constructing Mn redox cycling system (MCS) through community assembly remains to be elucidated. In this study, Mn-reducing strain MFG10 and Mn-oxidizing strain MFQ7 synergistically removed 94.67 % of 17β-estradiol (E2) within 12 h. Analysis of potential variations in Mn oxides suggested that MCS accelerated the production of reactive oxygen species (ROS) and Mn(III), which interacted to promote E2 removal. After continuous operation of the Mn ore-based immobilized bioreactor for 270 days, the experimental group (EG) achieved average removal efficiencies of 89.63 % and 97.57 % for NO 3 −-N and E2, respectively. High-throughput sequencing results revealed complex symbiotic relationships in EG. Community assembly significantly enhanced the metabolic and physiological activity of the bioreactor, which promoting the expression of core functions including nitrogen metabolism, Mn cycling and organic matter resistance. [ABSTRACT FROM AUTHOR]

[Display omitted] • Strain MFG10 exhibits excellent denitrification and manganese reduction abilities. • MnO 2 promoted the metabolism and induced extracellular secretion by MFG10. • SMP composition changed to improve degradability and redox activity. • The EET process was enhanced by the trapping-solubilizing MnO 2 mechanism of EPS. • Tryptophan-like proteins and PS become potential electron donor precursors. In this study, the manganese (Mn) reduction-coupled denitrification strategy of dissimilatory Mn reducing bacteria was insightfully investigated. Different parameters (MnO 2 level, pH, and temperature) were optimized by kinetic fitting to improve denitrification and Mn reduction effects. The 300 mg L−1 MnO 2 addition achieved 98.72% NO 3 –-N removal in 12 h, which was 54.62% higher than blank group without MnO 2. Scale-up studies showed that the metabolic activity of the bacteria was effectively enhanced by the addition of MnO 2. Besides the deepening of humification in the system, tryptophan-like protein and polysaccharide as potential electron donor precursors revealed remarkable contributions to the extracellular secretion-dependent denitrification process of DMRB. The effect of EPS on Mn reduction depends mainly on the capture of MnO 2 by the LB-EPS layer versus its dissolution in the TB-EPS layer. Ultimately, the EPS possess a dual effect of accelerated denitrification and Mn reduction efficiency due to the enhanced EET process. [ABSTRACT FROM AUTHOR]

[Display omitted] • A bibliometric analysis of Mn redox cycling coupled with nitrogen removal was conducted. • Mechanisms and influencing factors of Mn redox coupled nitrogen removal were discussed. • Application of Mn redox-driven nitrogen removal in sewage treatment was summarized. • Research gaps, challenges, and directions for future development were proposed. Nitrogen (N) pollution has emerged as one of the major threat to global sustainable development and has received increasing attention. Manganese (Mn) is the third most abundant transition metal on earth and microbially mediated Mn redox cycling coupled with N removal (MMnRCCNR) is a promising alternative that is not only economical and efficient but also has a low environmental impact. This review discusses the key influencing factors, theoretical basis, and mechanisms of Mn species as key mediators driving the biogeochemical cycle. In addition, the application and development trend of Mn redox cycling in the treatment of polluted water are summarized and presented, especially the combination of simultaneous N and micropollutant removal. The research hotspots and trends of Mn redox cycling mediated biological N removal are analyzed by bibliometric methods and the current research gaps, challenges, and future directions are identified. Overall, this review is expected to provide guide for further development and optimization of Mn redox-mediated microbial N removal processes, which will help to develop cost-effective N removal processes in the future to treat contaminated water. [ABSTRACT FROM AUTHOR]

[Display omitted] • Modified loofah with rough porous structure exhibited great immobilization effect. • Maximum NO 3 –-N, Mn (II) and TC removal efficiency were 91.97, 71.25, and 57.39%. • Adsorption, oxidation and co-metabolism were responsible for TC removal. • Zoogloea sp. was regarded as dominant contributor in the operation of bioreactor. • Metagenome revealed the potential of reactor for NO 3 –-N, Mn(II), and TC removal. The remediation of multiple pollutants in water, for instance, nitrate, heavy metals, and antibiotics is urgent and necessary for the global water resources protection. Herein, a modified loofah bioreactor was designed for simultaneous denitrification, manganese (Mn) oxidation, and tetracycline (TC) removal. The maximum removal efficiencies of NO 3 –-N (91.97%), Mn(II) (71.25%), and TC (57.39%) were achieved at a hydraulic retention time (HRT) of 9 h, Mn(II) concentration of 20 mg L-1, and TC concentration of 1 mg L-1. SEM and XRD were carried out to characterize the bioprecipitation in the operation of bioreactor. TC addition affected the gaseous denitrification products, dissolved organic matter, as well as reduced the OTU in the bioreactor. The Zoogloea were regarded as the dominant species in the microbial community and played an essential role in the operation of bioreactor. Metagenomic analysis proved the great potential for denitrification, manganese oxidation, and antibiotic removal of loofah bioreactor. [ABSTRACT FROM AUTHOR]

[Display omitted] • A new microbial immobilized carrier, PVA/SA@sponge cube was synthesized. • Immobilized bioreactor has the ability to simultaneously remove NO 3 −-N, Mn(II) and TC. • As an electron donor, Mn(II) was transformed into MnO 2 and MnCO 3 by microorganism. • Zoogloea was proved as the dominant contributor in reactor operation. The co-existence of nitrate, manganese (Mn), and antibiotics are of a wide concern. In this study, a denitrifying and manganese-oxidizing Zoogloea Q7 bacterium was immobilized using polyvinyl alcohol/sodium alginate with sponge cube (PVA/SA@sponge cube) in the reactor. The optimal operation parameters of the bioreactor were explored. Maximum nitrate, Mn(II), and tetracycline (TC) removal efficiencies of 93.00, 72.34, and 57.32% were achieved with HRT of 10 h, pH of 6.5, Mn(II) concentration of 20 mg L−1, and TC of 1 mg L−1, respectively. Fluorescence excitation-emission matrix (EEM) proved that the microorganism in the bioreactor was greatly active. Scanning electron microscope (SEM) images demonstrated that Zoogloea Q7 was commendably immobilized on the novel material. X-ray diffraction (XRD) analysis suggested that the bioprecipitate was mainly composed of MnO 2 and MnCO 3. Through high-throughput analysis, Zoogloea sp. Q7 was considered to be the dominant bacteria present in the bioreactor. [ABSTRACT FROM AUTHOR]