Nitrogen-deficient Environment Research Articles

Progress of Algaculture technology as Biofuel

As the problem of climate change becomes more and more serious, improving the carbon emission situation will be an effective way to solve various climate problems. Algal biofuels can build a complete carbon cycle and reduce carbon emissions. In this paper, the conditions required for microalgae cultivation and how diverse factors play a role in the growth rate and yield of microalgae were reviewed. And show how different factors like pH value, illumination, temperature, medium of culture, and nutrients in the medium affect the content of different substances in the final microalgae to help breed the matching microalgae. Macroscopically, this paper introduces both open raceway ponds and photobioreactors as microalgae cultivation systems and their respective characteristics. Microalgae will produce higher lipid content and hydrogen production capacity in different acid-base environments, respectively, and provide a nitrogen-deficient environment to further increase lipid production. The two-stage hybrid system combining an open raceway pond and photobioreactor has more obvious advantages in terms of growth rate and yield.

Interspecies Evolution and Networks Investigation of the Auxin Response Protein (AUX/IAA) Family Reveals the Adaptation Mechanisms of Halophytes Crops in Nitrogen Starvation Agroecological Environments

The maintenance of adaptability to the exposure to agroecological extreme environments is generally a feature after the long-term domestication of crops. Auxin influences plant growth in all environments. At present, the research on the auxin response factors (ARFs) has been very in-depth. However, there is still a large gap in the research on the origin, evolution, and regulatory networks of the Auxin-responsive protein (AUX/IAA) family. Here, we identified 495 AUX/IAAs from 19 representative species covering aquatic algae to angiosperms and found that they originated from early bryophytes and mainly expanded by polyploidy in angiosperms. In the domesticated crop quinoa, the evolutionary model of the IAA family is relatively independent and forms a robust regulatory network with auxin signals and energy metabolism pathways. In the nitrogen-deficient environment, CqIAAs (Chenopodium quinoa AUX/IAAs), auxin signals, and TCA pathway genes induced expression in young roots to promote root elongation and could regulate the balance of carbon and nitrogen metabolism to maintain the adaptation of early seedlings in poor environments. Furthermore, a rapidly evolving CqIAA (AUR62011942) not only has different expression levels in two quinoa seeds but also has a significant stress response when seedlings face nitrogen deficiency stress, which may be a key factor in the adaptive regulation of the barren environment. Our research provides valuable clues for understanding the origin, evolution, and functional innovation of auxin signaling and also provides a reference for future agricultural breeding in the context of global environmental changes.

Vegetative cells may perform nitrogen fixation function under nitrogen deprivation in Anabaena sp. strain PCC 7120 based on genome-wide differential expression analysis.

Nitrogen assimilation is strictly regulated in cyanobacteria. In an inorganic nitrogen-deficient environment, some vegetative cells of the cyanobacterium Anabaena differentiate into heterocysts. We assessed the photosynthesis and nitrogen-fixing capacities of heterocysts and vegetative cells, respectively, at the transcriptome level. RNA extracted from nitrogen-replete vegetative cells (NVs), nitrogen-deprived vegetative cells (NDVs), and nitrogen-deprived heterocysts (NDHs) in Anabaena sp. strain PCC 7120 was evaluated by transcriptome sequencing. Paired comparisons of NVs vs. NDHs, NVs vs. NDVs, and NDVs vs. NDHs revealed 2,044 differentially expressed genes (DEGs). Kyoto Encyclopedia of Genes and Genomes enrichment analysis of the DEGs showed that carbon fixation in photosynthetic organisms and several nitrogen metabolism-related pathways were significantly enriched. Synthesis of Gvp (Gas vesicle synthesis protein gene) in NVs was blocked by nitrogen deprivation, which may cause Anabaena cells to sink and promote nitrogen fixation under anaerobic conditions; in contrast, heterocysts may perform photosynthesis under nitrogen deprivation conditions, whereas the nitrogen fixation capability of vegetative cells was promoted by nitrogen deprivation. Immunofluorescence analysis of nitrogenase iron protein suggested that the nitrogen fixation capability of vegetative cells was promoted by nitrogen deprivation. Our findings provide insight into the molecular mechanisms underlying nitrogen fixation and photosynthesis in vegetative cells and heterocysts at the transcriptome level. This study provides a foundation for further functional verification of heterocyst growth, differentiation, and water bloom control.

The Influence of Alkaline Earth Elements on Electronic Properties of α-Si3N4 via DFT Calculation

We used density functional theory (DFT) calculations to study the influence of alkali earth metal element (AE) doping on the crystal structure and electronic band structure of α-Si3N4. The diversity of atomic radii of alkaline earth metal elements results in structural expansion when they were doped into the α-Si3N4 lattice. Formation energies of the doped structures indicate that dopants prefer to occupy the interstitial site under the nitrogen-deficient environment, while substitute Si under the nitrogen-rich environment, which provides a guide to synthesizing α-Si3N4 with different doping types by controlling nitrogen conditions. For electronic structures, energy levels of the dopants appear in the bottom of the conduction band or the top of the valence band or the forbidden band, which reduces the bandgap of α-Si3N4.

Influence of nitrogen on growth, biomass composition, production, and properties of polyhydroxyalkanoates (PHAs) by microalgae

This study sought to evaluate influence of nitrogen availability on cell growth, biomass composition, production, and the properties of polyhydroxyalkanoates during cultivation of microalgae Chlorella minutissima, Synechococcus subsalsus, and Spirulina sp. LEB-18. The cellular growth of microalgae reduced with the use of limited nitrogen medium, demonstrating that nitrogen deficiency interferes with the metabolism of microorganisms and the production of biomass. The biochemical composition of microalgae was also altered, which was most notable in the degradation of proteins and chlorophylls and the accumulation of carbonaceous storage molecules such as lipids and polyhydroxyalkanoates. Chlorella minutissima did not produce these polymers even in a nitrogen deficient environment. The largest accumulations of the polyhydroxyalkanoates occurred after a 15 days culture, with a concentration of 16% (dry cell weight) produced by the Synechococcus subsalsus strain and 12% by Spirulina sp. LEB-18. Polyhydroxyalkanoates produced by Synechococcus subsalsus and Spirulina sp. LEB-18 presented different thermal and physical properties, indicating the influence of producing strain on polyhydroxyalkanoates properties. The polymers obtained consisted of long chain monomers with 14 to 18 carbon atoms. This composition is novel, as it has not previously been found in PHAs obtained from Synechococcus subsalsus and Spirulina sp. LEB-18.

Photoautotrophic cultivating options of freshwater green microalgal Chlorococcum humicola for biomass and carotenoid production

ABSTRACTPhotoautotrophic cultivation of Chlorococcum humicola was performed in batch and continuous modes in different cultivating system arrangements to compare biomass and carotenoids’ concentration and their productivities. Batch result from stirred tank and airlift photobioreactors indicated the positive effect of increasing light intensity on growth and carotenoid production, whereas the finding from continuous cultivation indicated that carotenoid enhancement preferred high light intensity and nitrogen-deficient environment. The highest biomass (1.31 ± 0.04 g L−1) and carotenoid (4.59 ± 0.06 mg L−1) concentration as well as the highest productivities, 0.46 g L−1 d−1 for biomass and 1.61 mg L−1 d−1 for carotenoids, were obtained when maintaining high light intensity of 10 klx, BG-11 medium and 2% (v/v) CO2 simultaneously, while the highest carotenoid content (4.84 mg g−1) was associated with high light intensity and nitrogen-deficient environment, which was induced by feed-modified BG-11 growth medium containing nitrate 20 folds lower than the original medium. Finally, the cultivating system arranged into smaller stirred tank photobioreactors in series yielded approximately 2.5 folds increase in both biomass and carotenoid productivities relative to using single airlift photobioreactor with equivalent working volume and similar operating condition.

Decolorization of organic fertilizer using advanced oxidation process and its application for microalgae cultivation

Advanced oxidation using UV radiation in the presence of H2O2 was applied for decolorization of liquid fertilizer and the resulting liquid fertilizer was utilized to the cultivation of microalga Chlorella vulgaris and biodiesel production. The growth of C. vulgaris was enhanced in decolorized medium. The biomass productivity of C. vulgaris in AOP-treated PAL1 reached 124mg/L, which was 2.1 times higher than that in original PAL1, 58mg/L/day. Cellular lipid accumulation was increased in decolorized medium (from 6 to 30%), because fast growing cells consumed nitrogren faster in decolorized medium and thus lipid synthesis was triggered in nitrogen-deficient environment.

Light Quality Effect on Corn Growth as Influenced by Weed Species and Nitrogen Rate

<p>Corn-weed competition has often been characterized as the competition for limited resources such as light quantity, water, and nutrients. However, growing evidence suggests that light quality, specifically the red:far red ratio (R:FR), is a crucial component to corn-weed interactions. Additionally, a reduction in the R:FR has shown to down-regulate plant genes similarly to a nitrogen (N) deficient environment. A greenhouse study was conducted to evaluate the effect of N stress and R:FR from common waterhemp, velvetleaf, and volunteer corn on corn growth and development. The R:FR for all three weed species tended to be similar but lower than a weed-free treatment. However, observations from the spectral response curves demonstrated significant changes in the patterns of light reflected from each weed species. In the N-sufficient environment, early-season (V5 corn growth stage) R:FR from all three weed species reduced corn height, leaf chlorophyll content, and shoot biomass while increasing fibrous root biomass. However, in the N-deficient environment, no effects were observed on corn growth from changes in light quality, indicating N stress was a greater limiting factor. These results highlight the importance of the critical weed-free period and the need for proper early-season weed management.</p>

Evaluation of kojic acid production in a repeated-batch PCS biofilm reactor

In this study, kojic acid, a secondary metabolite as an industrially important compound, was produced by Aspergillus oryzae (A. oryzae), which was immobilized in plastic composite support (PCS) bioreactor. Nitrogen deficient medium was applied to increase the production of KA in PCS-immobilized bioreactor. The efficiency of immobilized culture for kojic acid (KA) production and the effect of morphology of A. oryzae on KA production were evaluated. After three cycles of cultivation, 83.47g/L of KA was produced in PCS bioreactor in nitrogen deficient medium with productivity of 3.09g/L/d, which is higher than free suspension culture in batch fermentation. The morphology of A. oryzae mycelium changed under nitrogen starvation. Feather-like mycelium was observed with increasing KA production. RNA expression (kojA and kojT) results indicated that the nitrogen deficient environment had strong influence on KA production on the transcriptional level. PCS immobilized fermentation system, which allowed a repeated-batch fermentation with higher production and productivity, is a potential tool in industrial production of KA.

Nitrogen-Deprivation Elevates Lipid Levels in Symbiodinium spp. by Lipid Droplet Accumulation: Morphological and Compositional Analyses

Stable cnidarian-dinoflagellate (genus Symbiodinium) endosymbioses depend on the regulation of nutrient transport between Symbiodinium populations and their hosts. It has been previously shown that the host cytosol is a nitrogen-deficient environment for the intracellular Symbiodinium and may act to limit growth rates of symbionts during the symbiotic association. This study aimed to investigate the cell proliferation, as well as ultrastructural and lipid compositional changes, in free-living Symbiodinium spp. (clade B) upon nitrogen (N)-deprivation. The cell proliferation of the N-deprived cells decreased significantly. Furthermore, staining with a fluorescent probe, boron dipyrromethane 493/503 (BODIPY 493/503), indicated that lipid contents progressively accumulated in the N-deprived cells. Lipid analyses further showed that both triacylglycerol (TAG) and cholesterol ester (CE) were drastically enriched, with polyunsaturated fatty acids (PUFA; i.e., docosahexaenoic acid, heneicosapentaenoic acid, and oleic acid) became more abundant. Ultrastructural examinations showed that the increase in concentration of these lipid species was due to the accumulation of lipid droplets (LDs), a cellular feature that have previously shown to be pivotal in the maintenance of intact endosymbioses. Integrity of these stable LDs was maintained via electronegative repulsion and steric hindrance possibly provided by their surface proteins. Proteomic analyses of these LDs identified proteins putatively involved in lipid metabolism, signaling, stress response and energy metabolism. These results suggest that LDs production may be an adaptive response that enables Symbiodinium to maintain sufficient cellular energy stores for survival under the N-deprived conditions in the host cytoplasm.

ABUNDANCES AND ISOTOPE RATIOS IN THE MAGELLANIC CLOUDS: THE STAR-FORMING ENVIRONMENT OF N 113

With the goal of deriving the physical and chemical conditions of star-forming regions in the Large Magellanic Cloud (LMC), a spectral line survey of the prominent star-forming region N 113 is presented. The observations cover parts of the frequency range from 85 GHz to 357 GHz and include 63 molecular transitions from a total of 16 species, among them are the spectra of rare isotopologues. Maps of selected molecular lines as well as the 1.2 mm continuum distribution are also presented. Molecular abundances in the core of the complex are consistent with a photon-dominated region in a nitrogen deficient environment. While carbon monoxide (CO) shows optical depths of the order of τ ∼ 10, 13CO is optically thin. The most prominent lines of carbon monosulfide (CS), HCN, and HCO+show signs of weak saturation (τ ∼ 0.5). Densities range from 5 × 103 cm−3 for CO to almost 106 for CS, HCN, and a few other species, indicating that only the densest regions provide sufficient shielding, even for some of the most common species. An ortho- to para-formaldehyde (H2CO) ratio of ∼ 3 hints at H2CO formation in a warm (≳ 40 K) environment. Isotope ratios are 12C/13C ∼ 49 ± 5, 16O/18O ∼2000 ± 250, 18O/17O ∼ 1.7 ± 0.2, and 32S/34S ∼ 15. Agreement with data from other star-forming clouds shows that the gas is well mixed in the LMC. The isotope ratios not only differ from those seen in the Galaxy, they also do not form a continuation of the trends observed with decreasing metallicity from the inner to the outer Galaxy. This implies that the outer Galaxy, even though showing an intermediate metallicity, is not providing a transition zone between the inner Galaxy and the metal-poor environment of the Magellanic Clouds. A part of this discrepancy is likely caused by differences in the age of the stellar populations in the outer Galaxy and the LMC. While, however, this scenario readily explains measured carbon and oxygen isotope ratios, nitrogen and sulfur still lack a self-consistent interpretation.

Aspergillus oryzae 배양물이 육계의 생산성, 분변의 미생물 성상 및 암모니아 가스 발생량에 미치는 영향

본 연구는 질소원 결핍 배지에서 배양되어 in vitro 실험상에서 항균 활력이 있는 것으로 증명된 Aspergillus oryzae 배양물을 질소원 공급 배지와 비교하여 육계의 증체, 사료 섭취량, 영양소 이용율, 유해 가스 생산 및 분내 미생물 균총 변화 등에 미치는 영향을 조사하기 위하여 시행되었다. 총 168수 2일령 육계를 7 처리구(대조구, 질소원 공급 배지에서 자란 Aspergillus oryzae 배양물(NAOF) 0.05, 0.1, 0.5%, 질소원 결핍 배지에서 자란 Aspergillus oryzae 배양물(NNAOF) 0.05, 0.1, 0.5%에 배치하였다. 본 실험 결과 Aspergillus oryzae 첨가로 사료의 기호성이 증가되었으며, Aspergillus oryzae 배양시 질소원 결핍 처리는 일반적인 배양 방법에 비하여 증체와 사료 기호성에 더욱 효과적으로 작용하였다. 영양소 소화율은 질소원 처리 구간의 유의적 차이는 없었지만, 대조구에 비하여 Aspergillus oryzae 배양물을 첨가시에 영양소의 소화율이 전반적으로 향상되었는데, 이러한 결과는 육계의 소장 및 대장의 pH 조절에 관여하고 유익균의 생장을 촉진하며, 유해균의 증식을 억제할 수 있는 효소나 대사산물이 분비되어 긍정적으로 작용하여 사료의 기호성 및 영양소의 소화율을 증진시킨 결과라고 추정할 수 있다. 처리에 따른 분내 총균수 변화는 유의적(p<0.05)인 차이를 보였으며, 균수는 NNAOF>NAOF>대조구순으로 나타났다. E. coli와 살모넬라에서는 Aspergillus oryzae 배양물 처리구가 대조구에 비해 현저하게(p<0.05) 감소되었고, 특히 NNAOP 처리구에서 가장 낮게 나타났다. 분내 암모니아 가스 발생량을 조사한 결과, 실험실적으로 검사할 수 있는 발생량은 대조구>NAOF>NNAOF 순으로 나타났다. 본 연구 결과는 NNAOF을 이용한 육계 생산은 생산성 향상과 더불어 환경 오염을 예방할 수 있는 방법임을 시사하므로 더욱 심도있는 연구가 필요한 것으로 판단된다. Current study was conducted to identify the effects of dietary supplementation of Aspergillus oryzae ferments (AOF) cultured under normal (NAOF) or nitrogen-deficient (NMAOF) environment on feed efficiency, nutrient digestibility for broiler chicks. Fecal microbes and ammonia gas production were also determined. A total of 168 male Avian chicks, 2-wk-old, were randomly assigned into 56 cages, three chicks per cage. There were seven treatments (Control, NAOF 0.05, 0.1, 0.5%, NMAOF 0.05, 0.1, 0.5%), with 8 replicates (cages) per treatment. There was no significant difference in nutrient digestibility between two AOF groups, but the digestibility was greatly(p<0.05) improved by AOF supplementation. Total microbial account significantly (p<0.05) differed between the treatment groups with the highest number for NNAOF, followed by NAOF and control. In the case of Escherichia coli and Salmonella, the AOF supplementation significantly (p<0.05) reduced their numbers in feces, with a particular reduction in NNAOF group. Levels of ammonia gas generation were in order of control>NAOP>NNAOP. The current data implied that AOF supplementation, particularly grown under nitrogen-deficient environment, would be a feasible way to improve feed efficiency for broiler production, as well as to reduce environmental cost. However, further studies remain for industrial application.

Biodegradation of RDX-contaminated wastes in a nitrogen-deficient environment

A feasible biological treatment process for RDX-contaminated wastes was demonstrated in a bench-scale system, using real wastewater of a munitions factory. The wastewater mixture tested included the nitramine RDX together with high levels of nitrate and various organic solvents such as cyclohexanone and acetone. The purpose of the study was to remove both RDX and nitrate in order to prevent groundwater contamination. A two-stage reactor system including an anoxic stage followed by an aerobic one was tested. The anoxic stage was aimed at removing nitrate by denitrification, using available carbon sources present in the waste mixture. Additional supply of carbon source (acetone) was required to support complete removal of nitrate. Further removal of residual organic was achieved in the aerobic stage together with total mineralization of RDX. Complete removal of nitrate in the anoxic stage was found to be crucial to RDX mineralization in the aerobic stage, since RDX was used solely as a nitrogen source. Additional carbon source (cyclohexanone) was also required in the aerobic stage to assure complete removal of RDX. The treatment scheme tested may be a cost-effective alternative to physico-chemical treatments such as carbon adsorption and UV destruction, commonly applied for explosives-contaminated wastes.

Biodegradation of RDX-contaminated wastes in a nitrogen-deficient environment

A feasible biological treatment process for ROX-contaminated wastes was demonstrated in a bench-scale system, using real wastewater of a munitions factory. The wastewater mixture tested included the nitramine RDX together with high levels of nitrate and various organic solvents such as cyclohexanone and acetone. The purpose of the study was to remove both RDX and nitrate in order to prevent groundwater contamination. A two-stage reactor system including an anoxic stage followed by an aerobic one was tested. The anoxic stage was aimed at removing nitrate by denitrification, using available carbon sources present in the waste mixture. Additional supply of carbon source (acetone) was required to support complete removal of nitrate. Further removal of residual organic was achieved in the aerobic stage together with total mineralization of RDX. Complete removal of nitrate in the anoxic stage was found to be crucial to RDX mineralization in the aerobic stage, since RDX was used solely as a nitrogen source. Additional carbon source (cyclohexanone) was also required in the aerobic stage to assure complete removal of RDX. The treatment scheme tested may be a cost-effective alternative to physico-chemical treatments such as carbon adsorption and UV destruction, commonly applied for explosives-contaminated wastes.

Semi-continuous and Continuous Production of Aspergillus niger Spores in Submerged Liquid Culture

SUMMARY: Sporulation of Aspergillus niger was induced in continuous tower fermenters by restricting growth with nitrate limitation. Semi-continuous production of spores was achieved in a single-stage fermentation by alternating full-nutrient and nitrogen-deficient media to the culture. Continuous spore production was obtained in a two-stage fermentation system using the first stage for the growth of vegetative mycelium under optimum conditions and the second, larger, stage for sporulation induction in a constant nitrogen-deficient environment. Spores were produced from much simplified sporulation structures. Using a new sporulation index (Ω), which relates spore numbers produced to the quantity of substrate utilized, the average production efficiency of the two-stage continuous system was shown to be more than twice that of the semi-continuous production system. The tower fermenter was shown to be ideal for controlling organism morphology, thus providing conditions which allowed the development of continuous fungal sporulation.