Search

Denitrification reactions commonly remove nitrate and other reactive nitrogen (Nr) from wastewater. The C/N ratio indicates the sufficiency of organic carbons to drive heterotrophic denitrification; a low C/N ratio frequently leads to poor denitrification performance in wastewater treatment. This study proposed and tested a novel Sharon&DSR (denitrifying sulfide removal) process, with nitrite generated by the Sharon reactions and sulfide from sulfur-reducing reactions for promoting the following nitrite-based denitrification and denitrifying sulfide removal (DSR) process. The present reactor can remove nitrate at an efficiency of 97.7 %-93.5 % at an influent C/N ratio of 0.646-0.737 over a 96-d continuous-flow test. The microbial community study reveals the functional strains corresponding to individual groups of critical reactions. The stoichiometry analysis reveals the potential to apply the nitrite-based DSR process for Nr removal from ultra-low C/N (<0.64) wastewaters, experimentally demonstrated in the present study with a C/N ratio of 0.16-0.39., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Excess nitrogenous compounds in municipal or industrial wastewaters can stimulate growth of denitrifying bacteria, in return, to convert potentially hazardous nitrate to inorganic nitrogen gas. To explore the community structure, distributions and succession of functional strains, and their interactions with other microbial communities, contemporary studies were performed based on detailed genomic analysis. This mini-review updated contemporary genomic studies on denitrifying genes in natural and engineered aquatic systems, with the constructed wetlands being the demonstrative system for the latter. Prospects for the employment of genomic studies on denitrifying systems for process design, optimization and development of novel denitrifying processes were discussed., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Pseudomonas sp. C27 is a facultative autotrophic bacterium (FAB) that can effectively conduct mixotrophic and heterotrophic denitrifying sulfide removal (DSR) reactions under anaerobic condition using organic matters and sulfide as electron donors. Micro-aeration was proposed to enhance DSR reaction by FAB; however, there is no experimental proof on the effects of micro-aeration on capacity of denitrifying sulfide removal of FAB on proteomic levels. The proteome in total C27 cell extracts was observed by two-dimensional gel electrophoresis. Differentially expressed protein spots and specifically expressed protein spots were identified by MALDI TOF/TOF MS. We identified 55 microaerobic-responsive protein spots, representing 55 unique proteins. Hierarchical clustering analysis revealed that 75% of the proteins were up-regulated, and 5% of the proteins were specifically expressed under micro-aerobic conditions. These enzymes were mainly involved in membrane transport, protein folding and metabolism. The noted expression changes of the microaerobic-responsive proteins suggests that C27 strain has a highly efficient enzyme system to conduct DSR reactions under micro-aerobic condition. Additionally, micro-aeration can increase the rates of protein synthesis and cell growth, and enhance cell defensive system of the strain., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Pseudomonas sp. C27 can effectively conduct mixotrophic denitrifying sulfide removal (DSR) reactions using both organic matters and sulfide as electron donors. This study conducted DSR tests using C27 and quantitatively analyzed the protein abundances at C/N = 1.26, 1.63 and 3.0. At C/N = 1.26, C27 principally adopted autotrophic denitrification pathway in DSR reaction. As C/N ratio was increased to 1.63, C27 enhanced heterotrophic denitrification pathway for removing nitrous compounds. As the C/N ratio was further increased to 3.0, C27 accelerated metabolism via coupled-cycles pathway. The C/N ratio for coupled-cycles pathway was estimated ranging 2.0–2.3 in the studied medium. Optimal C/N ratio of traditional DSR processes ranged 1.05–1.26. With the coupled-cycles pathway, the accessible C/N/S regime for C27 on DSR reactions is enlarged. Minor revision of the coupled-cycles pathway considering production of ammonium step was made. [ABSTRACT FROM AUTHOR]

The simultaneous removal of sulfate, nitrate and organic carbon by biological processes in engineered systems is a relatively new area of research. This study is the first to demonstrate that these biological processes occur in natural systems resulting in the remediation of polluted river water. Samples of water and sediment were collected from a 5 km-long section of Liming River, Daqing, China, in August and September, 2012. Sections with reduced sulfate concentration, autotrophic denitrification and heterotrophy, together with their dominant strains, were identified. Over a river section that was 3 km long, sulfate reduction (SR) and denitrifying sulfide removal (DSR) processes together removed approximately 2100 tons of sulfate, 2300 tons of nitrate, and 3200 tons of chemical oxygen demand (COD) from the river water annually. Microbial community was shifted to adapt to transformation of pollutants and point-source pollution in the studied river. [ABSTRACT FROM AUTHOR]

• Proteomic analysis for C27 under mixotrophic growth was conducted. • 47 proteins in nitrogen metabolism were identified by iTRAQ and LC-MS/MS. • Metabolism from external NO 3 − to N 2 and PO 4 3− with coupled NH 4 + cycle was noted. • C27 growth can be applied into numerous nitrite processes. Pseudomonas sp. C27 is a facultative autotrophic bacterium that can grow mixotrophically to undergo denitrifying sulfide removal (DSR) reactions with both organic matters and sulfide as electron donors. A detailed understanding of how the C27 strain simultaneously removes nitrogen, sulfur and carbon from water is critical for optimal DSR process design and implementation. This study is the first to reveal the pathways of nitrogen and sulfur metabolisms, identifying a total of 47 proteins that are related to the nitrogen metabolism and seven proteins to the sulfur metabolism of strain C27 using iTRAQ and LC-MS/MS techniques. The proposed pathway of nitrogen metabolism for strain C27 from external nitrate to nitrogen gas and phosphate with a coupled ammonia cycle is based on the identified proteins, and suggests that nitrate was not essential for nitrogen metabolism and could be replaced by nitrite as the sole nitrogen source for C27. [ABSTRACT FROM AUTHOR]