scholarly journals Diazotrophic Behaviour in a Non-Sterile Bioreactor: The Effect of O2-Availability

Processes ◽  
2021 ◽  
Vol 9 (11) ◽  
pp. 2039
Author(s):  
Amber Yasemin Shirin de Zoete ◽  
Hendrik Gideon Brink ◽  
Joshua Cornelus Beukes ◽  
Ignatius Leopoldus van Rooyen ◽  
Willie Nicol
Keyword(s):  
Carbon Sink ◽  
Experimental Conditions ◽  
Feed Composition ◽  
Operational Conditions ◽  
Transport Chain ◽  
Agricultural Applications ◽  
Protection Mechanisms ◽  
Biological Nitrogen ◽  
Energy Balances ◽  
Diazotrophic Growth

The behaviour of a locally isolated diazotrophic consortium was investigated with the prospect of agricultural applications. A repeatable culture was obtained in a non-sterile bioreactor. Metagenomic analysis indicated Chryseobacterium ssp. and Flavobacterium ssp. were the dominant species, making up approximately 50% of the microbial community. The oxygen supply was varied and mass-transfer limited growth was attained under all experimental conditions. Negligible amounts of aqueous metabolites were formed, indicating a high selectivity towards biomass production. High oxygen availability resulted in decreased growth efficiencies i.e., the specific energy requirements for biomass synthesis. This was attributed to reduced electron transport chain efficiencies and nitrogenase protection mechanisms. Mass and energy balances indicated that sessile biomass with a high C:N served as a carbon sink. The most efficient growth was measured at an aeration feed composition of 21% oxygen and 79% nitrogen. The study presents one of the only known investigations of operational conditions on diazotrophic growth in a non-sterile bioreactor. In addition, it provides a strong foundation for the development of a Biological Nitrogen Fixation process with scaling potential.

scholarly journals Kinetics of Non-Enzymatic Synthesis of Dipeptide Cbz-Phe-Leu with AOT Reversed Micelles

Processes ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 1003
Author(s):  
Michiaki Matsumoto ◽  
Tadashi Hano
Keyword(s):  
Enzymatic Synthesis ◽  
Maximum Yield ◽  
Side Reactions ◽  
Experimental Conditions ◽  
Operational Conditions ◽  
Ph Dependency ◽  
Optimum Water Content ◽  
Short Time ◽  
Kinetics Of ◽  
Aot Reversed Micelles

The non-enzymatic synthesis of N-benzyloxycarbonyl-L-phenylalanyl-L-leucine (Cbz-Phe-Leu) from lipophilic N-benzyloxycarbonyl-L-phenylalanine (Cbz-Phe) and hydrophilic L-leucine (Leu), by N, N’-dicyclohexylcarbodiimide (DCC) as a condensing agent, was carried out using a reversed micellar system composed of bis(2-ethylhexyl) sodium sulfosuccinate (AOT) as a surfactant and isooctane. We successfully synthesized Cbz-Phe-Leu in a short time and investigated the effects of its operational conditions, the DCC concentration, w0, and the pH on the kinetic parameters and the maximum yields. For dipeptide synthesis, we had to add an excess of DCC with the substrates because of the side reactions of Cbz-Phe. From the pH dependency of the reactivity, a partially cationic form of Leu was better for a synthesis reaction because of the enrichment of Leu at the interface by anionic AOT. The optimum water content on the dipeptide synthesis was w0 = 28 due to the competition of the peptide synthesis and the side reactions. The maximum yield of Cbz-Phe-Leu was 0.565 at 80 h under optimum experimental conditions.

Summer Wax Grafting of Loblolly Pine

1987 ◽  
Vol 11 (2) ◽  
pp. 96-99 ◽  
Author(s):  
Steven E. McKeand ◽  
J. B. Jett ◽  
Jerry R. Sprague ◽  
Michael N. Todhunter
Keyword(s):  
Pinus Taeda ◽  
Loblolly Pine ◽  
Experimental Conditions ◽  
Operational Conditions ◽  
Dormant Season ◽  
Polyethylene Bags ◽  
Pinus Taeda L ◽  
Grafting Methods

Abstract Wax grafting methods that have been routinely used for winter dormant season grafting of loblolly pine (Pinus taeda L.) have been developed for grafting of more succulent summer shoots. Under experimental conditions, scions covered with paraffin at approximately 185°F had significantlyhigher grafting success in one study and equal success in another study compared to scions covered with polyethylene bags or Parafilm® strips. Under operational conditions, grafting success of 85% was realized with summer wax grafting. Significant savings of time and money are possibleif summer wax grafting methods are used. South. J. Appl. For. 11(2):96-99.

Effect of Branch Orientation on Annular Two-Phase Flow in T-Junctions

1996 ◽  
Vol 118 (1) ◽  
pp. 166-171 ◽  
Author(s):  
F. Peng ◽  
M. Shoukri ◽  
A. M. C. Chan
Keyword(s):  
Annular Flow ◽  
Two Phase Flow ◽  
Mechanical Energy ◽  
Phase Flow ◽  
Two Phase ◽  
Experimental Conditions ◽  
Present Test ◽  
Modelling Studies ◽  
Pressure Changes ◽  
Energy Balances

Experimental data on dividing steam-water two-phase annular flow in T-junctions with horizontal inlet and downwardly inclined branches were obtained. The experiments were performed under experimental conditions which have not been examined before. The branch orientation was found to be a significant parameter affecting phase redistribution in the junction. Increasing the downward inclination of the branch was found to reduce the degree of phase separation in the junction under the present test conditions. This is caused by the nonuniform distribution of the liquid film thickness associated with the horizontal inlet annular flow. The phase redistribution data were compared with available models. The need for additional modelling studies was evident. The pressure changes of two-phase flow in the junction were closely correlated with the phase redistribution phenomenon. The data on pressure changes in the junction were correlated using simple models based on momentum and mechanical energy balances.

scholarly journals An A2O-MBR system for simultaneous biological nitrogen and phosphorus removal from brewery wastewater at various nitrate recirculation ratios

2021 ◽  
Vol 258 ◽  
pp. 08011
Author(s):  
Van Nu Thai Thien ◽  
Dang Viet Hung ◽  
Nguyen Thi Thanh Hoa ◽  
Thi Ha Nguyen ◽  
Phan Thanh Trong
Keyword(s):  
Industrial Wastewater ◽  
Oxygen Demand ◽  
Organic Loading Rate ◽  
Brewery Wastewater ◽  
Nitrogen And Phosphorus ◽  
Nitrogen And Phosphorus Removal ◽  
Operational Conditions ◽  
Solids Retention ◽  
Removal Efficiencies ◽  
Biological Nitrogen

Anaerobic/Anoxic/Oxic – Membrane BioReactor (A2O-MBR) system including A2O unit at short solids retention time (SRT) for accumulation of PO43--P and MBR at long SRT for nitrification of NH4+-N was used to enhance simultaneous removal of nitrogen and phosphorus from brewery wastewater. The model of A2O-MBR system made from polyacrylic with the capacity of 49.5 liters was operated with organic loading rate of 0.75 kgCOD/m3.day. Nitrate recycling ratio was increased from 100 to 300% while sludge recirculation ratio was maintained at 100%. The results showed that for the nitrate recycling ratios of 100, 200, 300%, average NH4+-N and total nitrogen (TN) removal efficiencies of the model were 95.7 and 72.4, 99.2 and 86.7, 99.3 and 89.6%, respectively. The removal efficiencies of chemical oxygen demand (COD) and total phosphorus (TP) were over 90 and 75%, respectively, regardless of nitrate recirculation ratio. The output values of COD, NH4+-N, TN and TP were within the limits of Vietnam National Technical Regulation on Industrial Wastewater (QCVN 40:2011/BTNMT), column A, throughout the experiments. The model with recommended system configuration and optimum operational conditions could treat not only nitrogen but also phosphorus well due to appropriate nitrate recycling ratios.

scholarly journals Experimental conditions affect the site of tetrazolium violet reduction in the electron transport chain of Lactococcus lactis

Microbiology ◽  
2009 ◽  
Vol 155 (9) ◽  
pp. 2941-2948 ◽  
Author(s):  
Sybille Tachon ◽  
Damien Michelon ◽  
Emilie Chambellon ◽  
Monique Cantonnet ◽  
Christine Mezange ◽  
...  
Keyword(s):  
Electron Transfer ◽  
Electron Transport ◽  
Lactococcus Lactis ◽  
Electron Transport Chain ◽  
Experimental Conditions ◽  
Plate Test ◽  
Tetrazolium Salts ◽  
Transport Chain ◽  
Reduction Mechanisms ◽  
Tetrazolium Violet

The reduction of tetrazolium salts to coloured formazans is often used as an indicator of cell metabolism during microbiology studies, although the reduction mechanisms have never clearly been established in bacteria. The objective of the present study was to identify the reduction mechanisms of tetrazolium violet (TV) in Lactococcus lactis using a mutagenesis approach, under two experimental conditions generally applied in microbiology: a plate test with growing cells, and a liquid test with non-growing (resting) cells. The results showed that in both tests, TV reduction resulted from electron transfer from an intracellular donor (mainly NADH) to TV via the electron transport chain (ETC), but the reduction sites in the ETC depended on experimental conditions. Using the plate test, menaquinones were essential for TV reduction and membrane NADH dehydrogenases (NoxA and/or NoxB) were partly involved in electron transfer to menaquinones. In this case, TV reduction mainly occurred outside the cells and in the outer part of the plasma membrane. During the liquid test, TV was directly reduced by NoxA and/or NoxB, probably in the inner part of the membrane, where NoxA and NoxB are localized. In this case, reduction was directly related to the intracellular NADH pool. Based on these findings, new applications for TV tests are proposed, such as NADH pool determination with the liquid test and the screening of mutants affected in menaquinone biosynthesis with the plate test. Preliminary results using other tetrazolium salts in the plate test showed that the reduction sites depended on the salt, suggesting that similar studies should be carried out with other tetrazolium salts so that the outcome of each test can be interpreted correctly.

scholarly journals Proteome Profiling of the Rhodobacter capsulatus Molybdenum Response Reveals a Role of IscN in Nitrogen Fixation by Fe-Nitrogenase

2015 ◽  
Vol 198 (4) ◽  
pp. 633-643 ◽  
Author(s):  
Marie-Christine Hoffmann ◽  
Eva Wagner ◽  
Sina Langklotz ◽  
Yvonne Pfänder ◽  
Sina Hött ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Biological Nitrogen Fixation ◽  
Rhodobacter Capsulatus ◽  
Nitrogenase Activity ◽  
Central Process ◽  
Content Type ◽  
Proteome Profiling ◽  
Biological Nitrogen ◽  
Diazotrophic Growth

ABSTRACTRhodobacter capsulatusis capable of synthesizing two nitrogenases, a molybdenum-dependent nitrogenase and an alternative Mo-free iron-only nitrogenase, enabling this diazotroph to grow with molecular dinitrogen (N2) as the sole nitrogen source. Here, the Mo responses of the wild type and of a mutant lacking ModABC, the high-affinity molybdate transporter, were examined by proteome profiling, Western analysis, epitope tagging, andlacZreporter fusions. Many Mo-controlled proteins identified in this study have documented or presumed roles in nitrogen fixation, demonstrating the relevance of Mo control in this highly ATP-demanding process. The levels of Mo-nitrogenase, NifHDK, and the Mo storage protein, Mop, increased with increasing Mo concentrations. In contrast, Fe-nitrogenase, AnfHDGK, and ModABC, the Mo transporter, were expressed only under Mo-limiting conditions. IscN was identified as a novel Mo-repressed protein. Mo control of Mop, AnfHDGK, and ModABC corresponded to transcriptional regulation of their genes by the Mo-responsive regulators MopA and MopB. Mo control of NifHDK and IscN appeared to be more complex, involving different posttranscriptional mechanisms. In line with the simultaneous control of IscN and Fe-nitrogenase by Mo, IscN was found to be important for Fe-nitrogenase-dependent diazotrophic growth. The possible role of IscN as an A-type carrier providing Fe-nitrogenase with Fe-S clusters is discussed.IMPORTANCEBiological nitrogen fixation is a central process in the global nitrogen cycle by which the abundant but chemically inert dinitrogen (N2) is reduced to ammonia (NH3), a bioavailable form of nitrogen. Nitrogen reduction is catalyzed by nitrogenases found in diazotrophic bacteria and archaea but not in eukaryotes. All diazotrophs synthesize molybdenum-dependent nitrogenases. In addition, some diazotrophs, includingRhodobacter capsulatus, possess catalytically less efficient alternative Mo-free nitrogenases, whose expression is repressed by Mo. Despite the importance of Mo in biological nitrogen fixation, this is the first study analyzing the proteome-wide Mo response in a diazotroph. IscN was recognized as a novel member of the molybdoproteome inR. capsulatus. It was dispensable for Mo-nitrogenase activity but supported diazotrophic growth under Mo-limiting conditions.

scholarly journals Correlating the Process Variables and Products Involved in the Fluid Catalytic Cracking of Waste Feeds

2018 ◽  
Author(s):  
José Ignacio Alvira ◽  
Idoia Hita ◽  
Elena Rodriguez ◽  
Jose M Arandes ◽  
Pedro Castaño
Keyword(s):  
Catalytic Cracking ◽  
Principal Component ◽  
Product Distribution ◽  
Vacuum Gasoil ◽  
Fluid Catalytic Cracking ◽  
Pyrolysis Oil ◽  
Scrap Tire ◽  
Feed Composition ◽  
Operational Conditions ◽  
Main Components

Associating the most influential parameters with the product distribution is of uttermost importance in complex catalytic processes such as fluid catalytic cracking (FCC). These correlations can lead to the information-driven catalyst screening, kinetic modeling and reactor design. In this work, a dataset of 104 uncorrelated experiments, with 64 variables, has been obtained in an FCC simulator using 6 types of feedstock (vacuum gasoil, polyethylene pyrolysis waxes, scrap tire pyrolysis oil, dissolved polyethylene and blends of the previous), 36 possible sets of conditions (varying contact time, temperature and catalyst/oil ratio) and 3 industrial catalysts. Principal component analysis (PCA) has been applied over the dataset, showing that the main components are associated with feed composition (27.41% variance); operational conditions (19.09%) and catalyst properties (12.72%). The variables of each component have been correlated with the indexes and yields of the products: conversion, octane number, aromatics, olefins (propylene) or coke, among others.

Gene Fitness of Azotobacter vinelandii Under Diazotrophic Growth

2021 ◽  
Author(s):  
Carolann M. Knutson ◽  
Meghan N. Pieper ◽  
Brett M. Barney
Keyword(s):  
Nitrogen Fixation ◽  
Azotobacter Vinelandii ◽  
Genetic Manipulation ◽  
Nitrogen Fixing ◽  
Obligate Aerobe ◽  
Dependent Growth ◽  
Metal Cofactors ◽  
Biological Nitrogen ◽  
Diazotrophic Growth ◽  
Reference Tool

Azotobacter vinelandii is a nitrogen-fixing free-living soil microbe that has been studied for decades in relation to biological nitrogen fixation (BNF). It is highly amenable to genetic manipulation, helping to unravel the intricate importance of different proteins involved in the process of BNF, including the biosynthesis of cofactors that are essential to assembling the complex metal cofactors that catalyze the difficult reaction of nitrogen fixation. Additionally, A. vinelandii accomplishes this feat while growing as an obligate aerobe, differentiating it from many of the nitrogen-fixing bacteria that are associated with plant roots. The ability to function in the presence of oxygen makes A. vinelandii suitable for application in various potential biotechnological schemes. In this study, we employed transposon sequencing (Tn-seq) to measure the fitness defects associated with disruptions of various genes under nitrogen-fixing dependent growth, versus growth with extraneously provided urea as a nitrogen source. The results allowed us to probe the importance of more than 3800 genes, revealing that many genes previously believed to be important, can be successfully disrupted without impacting cellular fitness. Importance These results provide insights into the functional redundancy in A. vinelandii , while also providing a direct measure of fitness for specific genes associated with the process of BNF. These results will serve as a valuable reference tool in future studies to uncover the mechanisms that govern this process.

scholarly journals The metabolic response of plants to oxygen deficiency

2002 ◽  
Vol 14 (2) ◽  
pp. 83-94 ◽  
Author(s):  
Carlos Antônio Ferreira de Sousa ◽  
Ladaslav Sodek
Keyword(s):  
Anaerobic Metabolism ◽  
Metabolic Response ◽  
Tricarboxylic Acid Cycle ◽  
Oxygen Deficiency ◽  
Future Research ◽  
Experimental Conditions ◽  
Terminal Electron Acceptor ◽  
Transport Chain ◽  
N Metabolism

Plants, under natural or experimental conditions, can be subject to a range of O2 concentrations from normal (normoxia) through deficient (hypoxia) to total absence (anoxia). Many metabolic processes are affected by O2 deficiency but the most studied events are those related to respiration and metabolism of N. In the absence of a terminal electron acceptor for the electron transport chain, the tricarboxylic acid cycle functions only partially and in both directions. Acidification of the cytosol occurs and pyruvate, the product of glycolysis, is transformed to lactate and ethanol, which represent the main fermentation reactions in plants. Alanine is the third most important product of anaerobic metabolism, resulting from high rates of amino acid interconversion in which transaminases such as alanine aminotransferase play an important role. The role of alanine accumulation under anaerobiosis is not clear and appears to be independent of the source of N whether NO3-, NH4+ or N2. How nitrate exerts its beneficial effect on tolerance of root hypoxia in waterlogged plants is still not clearly understood. Such aspects of N metabolism pose interesting challenges for future research on metabolic responses of plants to oxygen deficiency.

scholarly journals A Data-Driven Reaction Network for the Fluid Catalytic Cracking of Waste Feeds

Processes ◽  
2018 ◽  
Vol 6 (12) ◽  
pp. 243 ◽  
Author(s):  
José Alvira ◽  
Idoia Hita ◽  
Elena Rodríguez ◽  
José Arandes ◽  
Pedro Castaño
Keyword(s):  
Catalytic Cracking ◽  
Reaction Network ◽  
Principal Component ◽  
Vacuum Gasoil ◽  
Fluid Catalytic Cracking ◽  
Data Driven ◽  
Pyrolysis Oil ◽  
Scrap Tire ◽  
Feed Composition ◽  
Operational Conditions

Establishing a reaction network is of uttermost importance in complex catalytic processes such as fluid catalytic cracking (FCC). This step is the seed for a faithful reactor modeling and the subsequent catalyst re-design, process optimization or prediction. In this work, a dataset of 104 uncorrelated experiments, with 64 variables, was obtained in an FCC simulator using six types of feedstock (vacuum gasoil, polyethylene pyrolysis waxes, scrap tire pyrolysis oil, dissolved polyethylene and blends of the previous), 36 possible sets of conditions (varying contact time, temperature and catalyst/oil ratio) and three industrial catalysts. Principal component analysis (PCA) was applied over the dataset, showing that the main components are associated with feed composition (27.41% variance), operational conditions (19.09%) and catalyst properties (12.72%). The variables of each component were correlated with the indexes and yields of the products: conversion, octane number, aromatics, olefins (propylene) or coke, among others. Then, a data-driven reaction network was proposed for the cracking of waste feeds based on the previously obtained correlations.

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