Mechanism of trehalose-enhanced metabolism of heterotrophic nitrification-aerobic denitrification community under high-salt stress / 生物工程学报

Heterotrophic nitrification-aerobic denitrification (HN-AD) bacteria are aerobic microorganisms that can remove nitrogen under high-salt conditions, but their performance in practical applications are not satisfactory. As a compatible solute, trehalose helps microorganisms to cope with high salt stress by participating in the regulation of cellular osmotic pressure, and plays an important role in promoting the nitrogen removal efficiency of microbial populations in the high-salt environment. We investigated the mechanism of exogenous-trehalose-enhanced metabolism of HN-AD community under high-salt stress by starting up a membrane aerobic biofilm reactor (MABR) to enrich HN-AD bacteria, and designed a C150 experimental group with 150 μmol/L trehalose addition and a C0 control group without trehalose. The reactor performance and the community structure showed that NH4+-N, total nitrogen (TN) and chemical oxygen demand (COD) removal efficiency were increased by 29.7%, 28.0% and 29.1%, respectively. The total relative abundance of salt-tolerant HN-AD bacteria (with Acinetobacter and Pseudofulvimonas as the dominant genus) in the C150 group reached 66.8%, an 18.2% increase compared with that of the C0 group. This demonstrated that trehalose addition promoted the enrichment of salt-tolerant HN-AD bacteria in the high-salt environment to enhance the nitrogen removal performance of the system. In-depth metabolomics analysis showed that the exogenous trehalose was utilized by microorganisms to improve proline synthesis to increase resistance to high-salt stress. By regulating the activity of cell proliferation signaling pathways (cGMP-PKG, PI3K-Akt), phospholipid metabolism pathway and aminoacyl-tRNA synthesis pathway, the abundances of phosphoethanolamine, which was one of the glycerophospholipid metabolites, and purine and pyrimidine were up-regulated to stimulate bacterial aggregation and cell proliferation to promote the growth of HN-AD bacteria in the high-salt environment. Meanwhile, the addition of trehalose accelerated the tricarboxylic acid (TCA) cycle, which might provide more electron donors and energy to the carbon and nitrogen metabolisms of HN-AD bacteria and promote the nitrogen removal performance of the system. These results may facilitate using HN-AD bacteria in the treatment of high-salt and high-nitrogen wastewater.

Advances in denitrification microorganisms and processes / 生物工程学报

Denitrification is an indispensable part of most sewage treatment systems. The biological denitrification process has attracted much attention in the past decades due to the advantages such as cost-effectiveness, process simplicity, and absence of secondary pollution. This review summarized the advances on biological denitrification processes in recent years according to the different physiological characteristics and denitrification mechanisms of denitrification microorganisms. The pros and cons of different biological denitrification processes developed based on nitrifying bacteria, denitrifying bacteria, and anaerobic ammonia-oxidizing bacteria were compared with the aim to identify the best strategy for denitrification in a complex wastewater environment. The rapid development of synthetic biology provides possibilities to develop highly-efficient denitrifying strains based on mechanistic understandings. Combined with the applications of automatic simulation to obtain the optimal denitrification conditions, cost-effective and highly-efficient denitrification processed can be envisioned in the foreseeable future.

Characterization of a novel heterotrophic nitrifying and aerobically denitrifying bacterium, Halomonas sp. Z8, as a potential bioagent for wastewater treatment

Aim: The aim of the present study was to identify and characterize the functions of key microbes mediating nitrification.Methodology: After sampling the biofilm from a submerged biofilter in a marine aquaculture system, selective media were used to isolate microbial strains involved in nitrification. Isolates were identified using physiological and biochemical assays and sequencing of 16S rRNA gene. Nitrogen removal under different conditions was characterized. Nitrogen removal pathway was characterized by a 15N tracer experiment. Representation of key microbes in the biolfim was characterized by metagenomics analysis. Results: Single-factor tests showed that Halomonas sp. strain Z8 exhibited good heterotrophic nitrification and aerobic denitrification abilities, with maximum NH4+-N, NO2--N and No3--N removal rates of 2.37, 1.28 and 1.7 mg N l-1 hr-1, respectively. The 15N isotope tracer experiment confirmed the aerobic nitrogen removal pathway of strain Z8. Average NO3-removal efficiencies were all above 80% in an aerated moving bed bioreactor inoculated with strain Z8 and employed to treat synthetic marine aquaculture wastewater. Metagenomic microbial community analysis revealed that Halomonas sp. Z8 was one of the dominant taxa at genus level, suggesting a vital role in removing nitrate from bioreactor

Advances in heterotrophic nitrification-aerobic denitrifying bacteria for nitrogen removal under extreme conditions / 生物工程学报

Heterotrophic nitrification-aerobic denitrification (HN-AD) is an enrichment and breakthrough theory of traditional autotrophic nitrification heterotrophic denitrification. Heterotrophic nitrification-aerobic denitrifiers with the feature of wide distribution, strong adaptability and unique metabolic mechanism have many special advantages, including fast-growing, rapid biodegradability and long lasting activity, which can rapidly remove ammonia nitrogen, nitrate nitrogen (NO₃⁻-N) and nitrite nitrogen (NO₂⁻-N) under aerobic conditions simultaneously. Therefore, HN-AD bacteria show the important potential for denitrification under extreme conditions with high-salt, low-temperature or high-ammonia nitrogen environment, and HN-AD bacteria attract extensive attention in the field of biological denitrification of wastewater. In this review, we first introduce the previously reported HN-AD bacterial species which have denitrification performance in the extreme environments and state their typical metabolic mechanism. Then, we systematically analyze the nitrogen removal characteristics and potential under extreme conditions. We also briefly describe the progress in the application of HN-AD bacterial. Finally, we outlook the application prospects and research directions of HN-AD denitrification technology.

Complete genome sequence of the aerobically denitrifying thermophilic bacterium Chelatococcus daeguensis TAD1

ABSTRACT Chelatococcus daeguensis TAD1 is a themophilic bacterium isolated from a biotrickling filter used to treat NOx in Ruiming Power Plant, located in Guangzhou, China, which shows an excellent aerobic denitrification activity at high temperature. The complete genome sequence of this strain was reported in the present study. Genes related to the aerobic denitrification were identified through whole genome analysis. This work will facilitate the mechanism of aerobic denitrification and provide evidence for its potential application in the nitrogen removal.

Review of Research in Aerobic Denitrification by Microorganisms / 环境与健康杂志

Nitrogen pollution in water body can not only cause eutrophication but also has direct hazardous effects on animals and human beings. The removal of ammonium is an important process in modern wastewater treatment systems. It is generally achieved by a traditional treatment system of combination of two processes,aerobic nitrification and anoxic denitrification,but these processes are very complex and the cost is higher. In recent years,some new principles have been proposed,such as aerobic denitrification,anaerobic ammonium oxidation,heterotrophic nitrification,which make simultaneous nitrification-denitrification possible. The domestic and foreign study progress in aerobic denitrification was reviewed in this paper.

Advances in Denitrification Characteristics of Heterotrophic Nitrification Bacteria / 微生物学通报

Heterotrophic nitrification bacteria are able to utilize organic carbon sources to grow and produce hydroxylamine,nitrite and nitrate from nitrogen compounds,and most of them can also denitrify these products to gaseous nitrogen compounds simultaneously.Therefore,more and more attentions are paid to heterotrophic nitrification bacteria for wastewater treatment.This paper reviews the denitrification characteristics of some isolated heterotrophic nitrification bacteria,and analyzes the influence of various conditions to the heterotrophic nitrification bacteria,such as temperature,pH,DO,carbon sources,C/N,and inhibitors,etc.At last,the present situation and potential applications of wastewater treatment by heterotrophic nitrification bacteria are introduced.