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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] • 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 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]