scholarly journals Modeling of Dynamics of Nitrogenous Compounds in Microalgae Cells. 1. Batch Culture

2018 ◽  
Vol 13 (2) ◽  
pp. 348-359 ◽  
Author(s):  
R.P. Trenkenshu ◽  
A.S. Lelekov
Keyword(s):  
Nitrogen Supply ◽  
Exponential Growth Phase ◽  
Specific Rate ◽  
Structural Components ◽  
Nitrogenous Compounds ◽  
Concentration Changes ◽  
Culture Growth ◽  
Species Specific ◽  
Modeling Of Dynamics ◽  
Maximum Specific Rate

The work is focused on modeling of dynamics of nitrogenous compounds in microalgae cells. The model is based on the idea that all intracellular nitrogen can be considered as the sum of structural and reserve forms. The rate of nitrogen supply into the cell and the rate of its consumption for the synthesis of structural components are described in the form of linear splines and expressed through the ratio of reserve and structural forms. It is shown that species-specific parameters of the model are light-dependent values. Particular integrated solutions have been found for specific cases of nitrogen supply. The dynamics of all forms of intracellular nitrogen and nitrogen concentration in the medium follow the exponential law. The mathematical model for quantitative description of microalgae culture growth in the absence of nitrogen in the environment is proposed. The equations obtained using experimental data on the culture growth and nitrogen assimilation by cells of green microalgae Dunaliella salina and Scenedesmus obliquus have been verified. The proposed model allows to describe the dynamics of the concentration changes of structural, reserve and extracellular nitrogen in the cultivation of these species. For the exponential growth phase, the species-specific coefficients of the maximum specific rate of nitrogen supply into the cell and the maximum specific rate of the synthesis of structural components, which for D. salina amounted to: 0.42 day-1 and 0.55 day-1; for S. obliquus – 1.37 day-1 and 1.25 day-1 respectively have been determined. Differences of these parameters for two types of microalgae are due to different light conditions of their cultivation.

scholarly journals Dynamics Modeling of Nitrogen Compounds in Microalgae Cells. 2. Chemostat

2019 ◽  
Vol 14 (2) ◽  
pp. 450-463 ◽  
Author(s):  
A.S. Lelekov ◽  
R.P. Trenkenshu
Keyword(s):  
Growth Rate ◽  
Specific Growth Rate ◽  
Specific Growth ◽  
Nitrogen Compounds ◽  
Specific Rate ◽  
Dynamics Modeling ◽  
Cell Content ◽  
Classical Models ◽  
Species Specific ◽  
Maximum Specific Rate

The work focuses on dynamics modeling of nitrogen compounds in microalgae cells under chemostat conditions. The analysis of classical models (Michaelis-Menten, Monod, Droop), which describe the kinetics of substrate-dependent growth of microalgae, was carried out. Classical models are shown to be applicable provided that the physicochemical parameters of the medium such as temperature, cell irradiation, etc are constant. As an alternative approach, the possibility of using linear splines in kinetics modeling of nitrate absorption by microalgae is shown. For the conditions of the chemostat, particular solutions for the generalized model of the dynamics of nitrogen compounds in the cells of microalgae considered in the first part of the work were obtained, and boundary conditions for the culture growth at unlimited nitrogen were determined. For limited growth, the equation for both the dependence of the specific growth rate on the intracellular nitrogen content, which coincides in form with the Droop model and the dependence of the specific growth rate on the extracellular concentration of nitrogen, which coincides in form with the Monod model were obtained. The species-specific coefficients of the equations such as the maximum specific rate of nitrogen absorption, the maximum specific rate of synthesis of structural components, the maximum content of reserve forms of nitrogen, the minimum share of structural forms of nitrogen in the total cell content were determined.

Multiple fire-related cues stimulate germination in Chaenorhinum rubrifolium (Plantaginaceae), a rare annual in the Mediterranean Basin

2017 ◽  
Vol 27 (1) ◽  
pp. 26-38 ◽  
Author(s):  
Çağatay Tavşanoğlu ◽  
Gökhan Ergan ◽  
Ş. Serter Çatav ◽  
Golshan Zare ◽  
Köksal Küçükakyüz ◽  
...  
Keyword(s):  
Heat Shock ◽  
Mediterranean Basin ◽  
Soil Seed Bank ◽  
Light Conditions ◽  
Annual Species ◽  
Nitrogenous Compounds ◽  
Physiological Dormancy ◽  
The Mediterranean ◽  
Species Specific ◽  
The Mediterranean Basin

AbstractIn Mediterranean fire-prone ecosystems, annual species specific to post-fire habitats should have a soil seed bank and should be able to germinate after a fire. Therefore, various fire-related cues can be expected to stimulate germination in post-fire annuals. Germination patterns of the rare annual Chaenorhinum rubrifolium (Plantaginaceae) were examined in response to mechanical scarification, heat shock, aqueous smoke, nitrogenous compounds, gibberellic acid, karrikinolide (KAR1), and mandelonitrile (a cyanohydrin analogue, MAN) under dark and photoperiod conditions in the laboratory. Combinations of these treatments were also included in the experiment. Strong physiological dormancy in the seeds of C. rubrifolium was partially broken by several fire-related germination cues, including smoke and nitrate, under light conditions. KAR1 and MAN also stimulated germination, and the highest improvement in germination was achieved in the KAR1 treatment in the presence of light. Heat shock + smoke and KAR1 + MAN combinations had positive synergetic and additive effects on germination under light conditions, respectively. The light played a crucial role in the promotion of germination. The results suggest that multiple fire-related cues operate to stimulate germination in C. rubrifolium, an annual species from the Mediterranean Basin. However, the species may have a broader germination niche than a fire-restricted one.

scholarly journals Reconstruction of the Diaminopimelic Acid Pathway to Promote L-lysine Production in Corynebacterium Glutamicum

2021 ◽  
Author(s):  
Ning Liu ◽  
Ting-Ting Zhang ◽  
Zhi-Ming Rao ◽  
Wei-Guo Zhang ◽  
Jian-Zhong Xu
Keyword(s):  
Corynebacterium Glutamicum ◽  
Regulatory Protein ◽  
Lysine Biosynthesis ◽  
Diaminopimelic Acid ◽  
Specific Rate ◽  
Original Strain ◽  
Lysine Production ◽  
Final Strain ◽  
Acid Pathway ◽  
Maximum Specific Rate

Abstract Background: The dehydrogenase pathway and the succinylase pathway are involved in the synthesis of L-lysine in Corynebacterium glutamicum. Despite the low contribution rate to L-lysine production, the dehydrogenase pathway is favorable for its simple steps and great potentials to increase the production of L-lysine. Results: The aim of this work is to enhance the carbon flux in dehydrogenase pathway to promote L-lysine production. Firstly, the effect of ammonium (NH4+) concentration on L-lysine biosynthesis was investigated, and the results indicated that the biosynthesis of L-lysine can be promoted in high NH4+ environment. In order to reduce the requirement of NH4+, the nitrogen source regulatory protein AmtR was knocked out, resulting in an 8.5% increase in L-lysine production (i.e., 52.3±4.31 g/L). Subsequently, the dehydrogenase pathway was upregulated by blocking or weakening tetrahydrodipicolinate succinylase (DapD)-coding gene dapD and overexpressing the ddh gene to further enhance L-lysine biosynthesis. The final strain XQ-5-W4 could produce 189±8.7 g/L L-lysine with the maximum specific rate (qLys,max.) of 0.35±0.05 g/(g·h) in a 5-L jar fermenter. Conclusions: The L-lysine titer and qLys,max achieved in this study is about 25.2% and 59.1% higher than that of the original strain without enhancement of dehydrogenase pathway, respectively. The results indicated that the dehydrogenase pathway could serve as a breakthrough point to reconstruct the diaminopimelic acid (DAP) pathway and promote L-lysine production.

scholarly journals Reconstruction of the Diaminopimelic Acid Pathway to Promote L-lysine Production in Corynebacterium glutamicum

2021 ◽  
Vol 22 (16) ◽  
pp. 9065
Author(s):  
Ning Liu ◽  
Ting-Ting Zhang ◽  
Zhi-Ming Rao ◽  
Wei-Guo Zhang ◽  
Jian-Zhong Xu
Keyword(s):  
Corynebacterium Glutamicum ◽  
Regulatory Protein ◽  
Lysine Biosynthesis ◽  
Diaminopimelic Acid ◽  
Specific Rate ◽  
Original Strain ◽  
Lysine Production ◽  
Final Strain ◽  
Acid Pathway ◽  
Maximum Specific Rate

The dehydrogenase pathway and the succinylase pathway are involved in the synthesis of L-lysine in Corynebacterium glutamicum. Despite the low contribution rate to L-lysine production, the dehydrogenase pathway is favorable for its simple steps and potential to increase the production of L-lysine. The effect of ammonium (NH4+) concentration on L-lysine biosynthesis was investigated, and the results indicated that the biosynthesis of L-lysine can be promoted in a high NH4+ environment. In order to reduce the requirement of NH4+, the nitrogen source regulatory protein AmtR was knocked out, resulting in an 8.5% increase in L-lysine production (i.e., 52.3 ± 4.31 g/L). Subsequently, the dehydrogenase pathway was upregulated by blocking or weakening the tetrahydrodipicolinate succinylase (DapD)-coding gene dapD and overexpressing the ddh gene to further enhance L-lysine biosynthesis. The final strain XQ-5-W4 could produce 189 ± 8.7 g/L L-lysine with the maximum specific rate (qLys,max.) of 0.35 ± 0.05 g/(g·h) in a 5-L jar fermenter. The L-lysine titer and qLys,max achieved in this study is about 25.2% and 59.1% higher than that of the original strain without enhancement of dehydrogenase pathway, respectively. The results indicated that the dehydrogenase pathway could serve as a breakthrough point to reconstruct the diaminopimelic acid (DAP) pathway and promote L-lysine production.

Étude de quelques aspects du métabolisme carboné et azoté chez l'Arceuthobium oxycedri, gui nain du genévrier

1992 ◽  
Vol 70 (8) ◽  
pp. 1709-1716
Author(s):  
L. Rey ◽  
A. Sadik ◽  
A. Fer ◽  
S. Renaudin
Keyword(s):  
Amino Acids ◽  
Photosynthetic Activity ◽  
Nitrogen Nutrition ◽  
Nitrogen Supply ◽  
Dwarf Mistletoe ◽  
Gas Exchanges ◽  
Nitrogenous Compounds ◽  
Slow Development ◽  
Carbon Nutrition ◽  
Glutamate Oxalacetate Transaminase

In juniper dwarf mistletoe, Arceuthobium oxycedri (DC) M. Bieb., a hemiparasitic and epiphytic Angiosperm characterized by very reduced and slow development, the chlorophyll content of the shoots is relatively high for a parasitic plant. However, gas exchanges reveal a low net gain in carbon, and the real photosynthetic intensity is only about 1.5 to 2 times higher than the respiratory intensity in these organs. In the endophytic system, which is also chlorophyllous, a small amount of photosynthetic activity also occurs. By studying 14CO2 assimilation and carboxylase activities in both organs, it was possible to determine the ability of the parasite to satisfy part of its carbon requirements. Following the administration of 14CO2, radioactivity was mainly recovered in carbohydrates and to a lesser extent in organic acids and amino acids. This demonstrates that A. oxycedri has some autonomy for the fixation and distribution of carbon into various compounds. On the other hand, the parasite, since it is epiphytic, is completely dependent upon its host for nitrogen. The study of the activities of the key enzymes of nitrogen metabolism ([Formula: see text] and [Formula: see text] reductases, glutamine synthetase, glutamate dehydrogenase, glutamate-oxalacetate transaminase) shows that nitrogen supply from the host certainly occurs mainly in the form of reduced nitrogenous compounds (ammonia and (or) aminated organic compounds). The numerous labelled amino acids recovered after administration of 14CO2 show that A. oxycedri is able to redistribute the imported nitrogen in various ways. Key words: Arceuthobium oxycedri, parasitic Angiosperms, carbon nutrition, nitrogen nutrition.

scholarly journals Lipid peroxide formation in microsomes. General considerations

1969 ◽  
Vol 113 (2) ◽  
pp. 315-324 ◽  
Author(s):  
E. D. Wills
Keyword(s):  
Liver Microsomes ◽  
Lipid Peroxide ◽  
Maximum Activity ◽  
Specific Rate ◽  
Peroxide Formation ◽  
Unsaturated Lipids ◽  
Low Concentrations ◽  
Transport Chain ◽  
Maximum Specific Rate ◽  
Lipid Peroxide Formation

1. Liver microsomes form lipid peroxide when incubated with ascorbate or NADPH, but not with NADH. Increasing the concentration of ascorbate beyond the optimum (0·5mm) decreases the rate of lipid peroxide formation, but this effect does not occur with NADPH. Other reducing agents such as p-phenylenediamine or ferricyanide were not able to replace ascorbate and induce lipid peroxide formation. 2. The rate of ascorbate-induced peroxidation is optimum at pH6·0 whereas the rate of the NADPH system is optimum at pH7·0. Both systems require phosphate for maximum activity. 3. Lipid peroxide formation occurs at the maximum specific rate in very dilute microsome suspensions (0·15mg. of protein/ml.). 4. Treatment of microsomes with deoxycholate and other detergents causes membrane disintegration and inhibits lipid peroxide formation. 5. Lipid peroxide formation is accompanied by a rapid uptake of oxygen and there is a large excess of oxygen utilized for each molecule of malonaldehyde measured in the peroxide method. 6. Boiled microsomes form lipid peroxide in the presence of ascorbate, but not if NADPH is added. 7. Lipid peroxide formation induced by NADPH is strongly inhibited by p-chloromercuribenzoate, weakly inhibited by N-ethylmaleimide and unaffected by iodoacetamide. Ascorbate-induced peroxidation in untreated microsomes is unaffected by p-chloromercuribenzoate, but inhibited if boiled microsomes are used. These experiments may be interpreted on the basis that a ferredoxin-type protein forms part of the system in which NADPH induces lipid peroxide formation. 8. Most heavy-metal ions, with the exception of inorganic iron (Fe2+ or Fe3+), which activates, inhibit both ascorbate-induced and NADPH-induced peroxidation. Mg2+ increases the rate of peroxidation whereas Ca2+ inhibits it. 9. Lipid peroxide formation is inhibited strongly by GSH and weakly by cysteine. Ascorbate-induced peroxidation is much more sensitive than NADPH-induced peroxidation. 10. Peroxidation is strongly inhibited by addition of low concentrations (0·01–0·1mm) of cytochrome c or of haemoglobin. 11. It is considered that lipid peroxide formation occurs as a result of the operation of the microsomal electron-transport chain switching from hydroxylation to oxidize unsaturated lipids of the endoplasmic reticulum.

scholarly journals Preparation procedure to obtain iron nanopowder under non-isothermal conditions

2021 ◽  
pp. 28-35
Author(s):  
Тиен Хиеп Нгуен ◽  
Ван Минь Нгуен ◽  
Мань Хунг Нгуен ◽  
Виталий Николаевич Данчук
Keyword(s):  
Activation Energy ◽  
Hydrogen Reduction ◽  
Reduction Process ◽  
Preparation Procedure ◽  
Specific Rate ◽  
Temperature Range ◽  
Isothermal Conditions ◽  
Fe Nanoparticles ◽  
Mixed Reaction ◽  
Maximum Specific Rate

The kinetics for the procedure of preparing iron nanopowder from α-FeOOH by hydrogen reduction under non-isothermal conditions were studied. The reduction of α-FeOOH nanopowder was shown to occur within the temperature range from 180 to 550 °С, with a maximum specific rate value attained at 500 °С. The activation energy for the reduction process α-FeOOH nanopowder was measured to be ~43 kJ/mol, evidencing a mixed reaction mode. Performing the reduction of α-FeOOH at 500 °С accelerated the process while ensuring the required properties of the product obtained. The Fe nanoparticles thus prepared were of rounded shape, the size ranging from 70 to 100 nm.

028. Cytokine networks and regulation of spermatogenesis - what should we really believe?

2005 ◽  
Vol 17 (9) ◽  
pp. 70
Author(s):  
M. P. Hedger
Keyword(s):  
Growth Factors ◽  
Germ Cells ◽  
Sertoli Cells ◽  
Seminiferous Epithelium ◽  
Specific Rate ◽  
Development In Vitro ◽  
Cytokine Networks ◽  
Species Specific ◽  
Key Events

Spermatogenesis is a complex yet highly organised process involving intimate interactions between the supporting Sertoli cells and germ cells at various stages of development. The repeating pattern of the cycle of the seminiferous epithelium is due to the fact that spermatogonia enter spermatogenesis at regularly spaced intervals and proceed through the process at a species-specific rate. How this degree of coordination is maintained remains poorly understood, but recent evidence has focussed attention on the role of growth factors produced by the Sertoli cells and germ cells. Several of these growth factors, such as interleukin-1α (IL-1α), IL-6, tumour necrosis factor (TNFα) and activin A, are also inflammatory cytokines. This has led some researchers to question the physiological significance of these data with respect to normal testicular function. For example, in spite of the fact that IL-1α is produced by the Sertoli cell and regulates spermatogonial proliferation and development in vitro, mice lacking the IL-1R, and hence unresponsive to IL-1α, possess relatively normal fertility. So what role, if any, do these cytokines play in the normal testis, or are they only important during inflammation? It is quite evident that these cytokines have stimulatory and/or inhibitory effects on spermatogonial and spermatocyte development. These cytokines also interact at multiple levels within each other’s signalling pathways and have considerable redundancy of action. Moreover, expression of these cytokines varies across the cycle of the seminiferous epithelium, with major changes in production coinciding with two key events within the cycle: the release of sperm from the epithelium, and the major peaks of DNA synthesis by spermatogonia and preleptotene spermatocytes. It is therefore possible to hypothesise that release of sperm and resorption of the residual cytoplasm triggers a self-regulating inflammatory cascade within the epithelium that initiates and then modulates the next round of spermatogenic development, ensuring that spermatogonia enter the process at the appropriately spaced intervals.

Modified equation of chlorophyll content in microalgal biomass under light limitation

2020 ◽  
pp. 17-24
Author(s):  
Alexander S. Lelekov ◽  
Rudolf P. Trenkenshu ◽  
Tatyana M. Novikova
Keyword(s):  
Chlorophyll Concentration ◽  
Arthrospira Platensis ◽  
Light Limitation ◽  
Specific Rate ◽  
Microalgal Biomass ◽  
Basic Model ◽  
Microalgae Biomass ◽  
Rate Of Photosynthesis ◽  
Species Specific ◽  
Irradiation Parameter

The paper presents a modified mathematical model of light-dependent chlorophyll concentration in the microalgae biomass. The basic model is based on the concept of biomass as a sum of reserve and structural components. Considering that part of the structural biomass can turn into a reserve, the minimum irradiation parameter (“photosynthesis compensation point”) is added to the basic equation. Verification of the model on experimental data for turbidostat cultures of Tetraselmis viridis and Arthrospira platensis allowed us to evaluate species-specific coefficients. The obtained coefficient values are similar for both species. The share of chlorophyll in structural biomass is about 2 %, the maximum share of structural forms of biomass is 84 %, the economic conversion factor of reserve biomass to structural is 80–90 %, and the maximum specific rate of photosynthesis is 14–20 times higher than the rate of endogenous consumption of biomass.

Development of model for bioremediation of crude oil using moringa extract

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Crude Oil ◽  
Moringa Oleifera ◽  
High Efficiency ◽  
Research Work ◽  
Specific Rate ◽  
Rate Laws ◽  
Oil Spillage ◽  
New Research ◽  
Soil Constituents ◽  
Maximum Specific Rate

Crude oil spillage on land is a major undeniable challenge we face in the Niger Delta, this is as a result of the oil exploration and exploitation activity done by the big oil multinationals and also those done by indigenous private firms, the petroleum could find its way to the soil via occurrences including pipeline leakages and explosions, corrosion of underground pipes transporting crude oil and petroleum product and also it could come purely in form of untreated industrial waste. As a result of the foregoing research work was conducted using Moringa leave extract, and the component of interest included phosphates, potassium and nitrogen which are the major stimulators of bioremediation, were found to be abundant in the Moringa Oleifera leave extract. The application of Moringa leave extract was found to be useful in the enhancing of crude oil polluted lands, and by so doing it facilitates the rehabilitation of the contaminated soil as well as reinstating the soil constituents for agricultural purposes. This is a new research investigation which show high efficiency in bioremediation program the maximum specific rate and the rate constants as well as they overall order of the bioremediation reaction were determined, using the principle of the rate laws as well as they Monod’s equation from which the line waver burke plot was obtained. Therefore the experiment as well as the theoretical model developed can be used to monitor, predict and simulate the rate of degradation of hydrocarbons present in a polluted soil undergoing bioremediation under the influence of Moringa Oleifera leave extract.

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