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An Exploration of Seaweed Polysaccharides Stimulating Denitrifying Bacteria for Safer Nitrate Removal.
Zhang, H, Song, L, Chen, X, Li, P
Molecules (Basel, Switzerland). 2021;(11)
Abstract
Excessive use of nitrogen fertilizer in intensively managed agriculture has resulted in abundant accumulation of nitrate in soil, which limits agriculture sustainability. How to reduce nitrate content is the key to alleviate secondary soil salinization. However, the microorganisms used in soil remediation cause some problems such as weak efficiency and short survival time. In this study, seaweed polysaccharides were used as stimulant to promote the rapid growth and safer nitrate removal of denitrifying bacteria. Firstly, the growth rate and NO3--N removal capacity of three kinds of denitrifying bacteria, Bacillus subtilis (BS), Pseudomonas stutzeri (PS) and Pseudomonas putida (PP), were compared. The results showed that Bacillus subtilis (BS) had a faster growth rate and stronger nitrate removal ability. We then studied the effects of Enteromorpha linza polysaccharides (EP), carrageenan (CA), and sodium alginate (AL) on growth and denitrification performance of Bacillus subtilis (BS). The results showed that seaweed polysaccharides obviously promoted the growth of Bacillus subtilis (BS), and accelerated the reduction of NO3--N. More importantly, the increased NH4+-N content could avoid excessive loss of nitrogen, and less NO2--N accumulation could avoid toxic effects on plants. This new strategy of using denitrifying bacteria for safely remediating secondary soil salinization has a great significance.
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2.
How does nitrate regulate plant senescence?
Wen, B, Xiao, W, Mu, Q, Li, D, Chen, X, Wu, H, Li, L, Peng, F
Plant physiology and biochemistry : PPB. 2020;:60-69
Abstract
Nitrogen is an essential macronutrient for plant growth and development and plays an important role in the whole life process of plants. Nitrogen is an important component of amino acids, chlorophyll, plant hormones and secondary metabolites. Nitrogen deficiency leads to early senescence in plants, which is accompanied by changes in gene expression, metabolism, growth, development, and physiological and biochemical traits, which ensures efficient nitrogen recycling and enhances the plant's tolerance to low nitrogen. Therefore, it is very important to understand the adaptation mechanisms of plants under nitrogen deficiency for the efficient utilization of nitrogen and gene regulation. With the popularization of molecular biology, bioinformatics and transgenic technology, the metabolic pathways of nitrogen-deficient plants have been verified, and important progress has been made. However, how the responses of plants to nitrogen deficiency affect the biological processes of the plants is not well understood. The current research also cannot completely explain how the metabolic pathways identified show other reactions or phenotypes through interactions or cascades after nitrogen inhibition. Nitrate is the main form of nitrogen absorption. In this review, we discuss the role of nitrate in plant senescence. Understanding how nitrate inhibition affects nitrate absorption, transport, and assimilation; chlorophyll synthesis; photosynthesis; anthocyanin synthesis; and plant hormone synthesis is key to sustainable agriculture.
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3.
Evaluating simultaneous chromate and nitrate reduction during microbial denitrification processes.
Peng, L, Liu, Y, Gao, SH, Chen, X, Ni, BJ
Water research. 2016;:1-8
Abstract
Sulfur-based autotrophic denitrification and heterotrophic denitrification have been demonstrated to be promising technological processes for simultaneous removal of nitrate NO3(-) and chromate (Cr (VI)), two common contaminants in surface and ground waters. In this work, a mathematical model was developed to describe and evaluate the microbial and substrate interactions among sulfur oxidizing denitrifying organism, methanol-based heterotrophic denitrifiers and chromate reducing bacteria in the biofilm systems for simultaneous nitrate and chromate removal. The concomitant multiple chromate reduction pathways by these microbes were taken into account in this model. The validity of the model was tested using experimental data from three independent biofilm reactors under autotrophic, heterotrophic and mixotrophic conditions. The model sufficiently described the nitrate, chromate, methanol, and sulfate dynamics under varying conditions. The modeling results demonstrated the coexistence of sulfur-oxidizing denitrifying bacteria and heterotrophic denitrifying bacteria in the biofilm under mixotrophic conditions, with chromate reducing bacteria being outcompeted. The sulfur-oxidizing denitrifying bacteria substantially contributed to both nitrate and chromate reductions although heterotrophic denitrifying bacteria dominated in the biofilm. The mixotrophic denitrification could improve the tolerance of autotrophic denitrifying bacteria to Cr (VI) toxicity. Furthermore, HRT would play an important role in affecting the microbial distribution and system performance, with HRT of higher than 0.15 day being critical for a high level removal of nitrate and chromate (over 90%).
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4.
Evaluating the Role of Microbial Internal Storage Turnover on Nitrous Oxide Accumulation During Denitrification.
Liu, Y, Peng, L, Guo, J, Chen, X, Yuan, Z, Ni, BJ
Scientific reports. 2015;:15138
Abstract
Biological wastewater treatment processes under a dynamic regime with respect to carbon substrate can result in microbial storage of internal polymers (e.g., polyhydroxybutyrate (PHB)) and their subsequent utilizations. These storage turnovers play important roles in nitrous oxide (N2O) accumulation during heterotrophic denitrification in biological wastewater treatment. In this work, a mathematical model is developed to evaluate the key role of PHB storage turnovers on N2O accumulation during denitrification for the first time, aiming to establish the key relationship between N2O accumulation and PHB storage production. The model is successfully calibrated and validated using N2O data from two independent experimental systems with PHB storage turnovers. The model satisfactorily describes nitrogen reductions, PHB storage/utilization, and N2O accumulation from both systems. The results reveal a linear relationship between N2O accumulation and PHB production, suggesting a substantial effect of PHB storage on N2O accumulation during denitrification. Application of the model to simulate long-term operations of a denitrifying sequencing batch reactor and a denitrifying continuous system indicates the feeding pattern and sludge retention time would alter PHB turnovers and thus affect N2O accumulation. Increasing PHB utilization could substantially raise N2O accumulation due to the relatively low N2O reduction rate when using PHB as carbon source.
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5.
[Advances in studies on accumulation and leaching of nitrate in farming soil].
Zhang, Q, Chen, X, Shen, S
Ying yong sheng tai xue bao = The journal of applied ecology. 2002;(2):233-8
Abstract
Nitrate leaching in farming soil is the main reason resulting in ground water pollution of nitrate. The main factors, which can affect nitrate accumulation and leaching greatly, include fertilization, precipitation, irrigation, soil characteristics, and cultivation system. Superfluous nitrogen in soil caused either by using chemical fertilizer and manure solely or compost will result in nitrate accumulation. Cultivation and plow systems also can affect the process of nitrate accumulating and leaching. Down flows due to irrigation or precipitation are the necessary condition and carrier for transference and leaching of accumulated nitrate in soil. Great pores are the main channels for down flows. These factors always work corporately. Mathematical model, which has been developed quickly and used widely, may be a good method to study and predict nitrate leaching in farming land.