Experimental and analytical investigation of an immiscible displacement process in real structure micromodels

The recovery of oil from a reservoir can be accomplished with various methods, one of the most commonly applied types being waterflooding. A common theory used to describe immiscible displacement is the Buckley–Leverett theory. A brand new type of micromodel, generated and fabricated by using a micro-computer tomography (μCT) image stack of a real sandstone core, was used to conduct immiscible displacement experiments. Critical logging data were recorded, and a high-resolution camera took pictures of the displacement process. In an image processing tool (MATLAB), an algorithm was developed to evaluate the pictures of the experiment and to examine the changes in the saturations of the displacing and the displaced fluid. The main objective of the displacement experiment was to validate the new microchip in two-phase displacement experiments and to assess the feasibility of the image processing algorithm. This was performed by comparing the results of the experimental to the analytical solutions, which were derived from the Buckley–Leverett theory. The comparison of the results showed a good match between the two types of solutions. The applicability of the analytical results to the experimental procedures was observed. Additionally, the usage of the newly fabricated micromodel and its potential to visualize the fluid flow behavior in porous media were assessed

Coupled model for microbial growth and phase mass transfer in pressurized batch reactors in the context of underground hydrogen storage

A rising interest in a strong hydrogen economy as a part of the future net-zero economy results in an increasing necessity to store hydrogen as a raw material or an energy carrier. Experience and studies show that storing hydrogen in deep underground sites could enable microbial conversion of hydrogen. To predict and examine the loss of hydrogen, laboratory studies, and analysis are essential. A growth model is required to interpret batch or chemostat experiments. With this model, the parameters of microbial growth, and the conversion of hydrogen can be specified. This study presents experiments with methanogens and a hydrogen/carbon dioxide gas mixture performed in batch reactors. Further, the microbial growth was modeled by a double Monod model with hydrogen and carbon dioxide as the limiting substrates. As the amount of carbon dioxide dissolved in the water phase can not be neglected, both phases were considered in the proposed model. The mass-transfer rate between the gas and water phase was implemented by a linear relation including the concentrations in both phases and the mass-transfer coefficient. With the resulting coupled model, it was possible to match the pressure behavior in the reactor and conclude the microbial growth kinetics. Two types of methanogenic species were tested to validate the model. The mass transfer coefficient proves to impact the growth behavior in porous media. The mathematical model and experimental data are necessary to determine the growth rate and yield coefficient

Structural and functional insights into asymmetric enzymatic dehydration of alkenols

The asymmetric dehydration of alcohols is an important process for the direct synthesis of alkenes. We report the structure and substrate specificity of the bifunctional linalool dehydratase isomerase (LinD) from the bacterium Castellaniella defragrans that catalyzes in nature the hydration of β-myrcene to linalool and the subsequent isomerization to geraniol. Enzymatic kinetic resolutions of truncated and elongated aromatic and aliphatic tertiary alcohols (C5-C15) that contain a specific signature motif demonstrate the broad substrate specificity of LinD. The three-dimensional structure of LinD from Castellaniella defragrans revealed a pentamer with active sites at the protomer interfaces. Furthermore, the structure of LinD in complex with the product geraniol provides initial mechanistic insights into this bifunctional enzyme. Site-directed mutagenesis confirmed active site amino acid residues essential for its dehydration and isomerization activity. These structural and mechanistic insights facilitate the development of hydrating catalysts, enriching the toolbox for novel bond-forming biocatalysis

Effect of acupuncture regarding the range of motion after knee endoprosthesis during the first week after Implantation

In einer randomisierten und doppelblinden Studie wurde der Effekt der frühen postoperativen Akupunktur auf die passive Beugefähigkeit im Kniegelenk und Schmerzreduktion nach Knieprothesenimplantation untersucht. Der Untersuchungszeitraum lag zwischen dem 2. und 6. postoperativen Tag. In der Auswertung der Studie zeigte sich eine Verbesserung der Beugefähigkeit unter Verringerung der Ruheschmerzintensität in der Verum-Akupunkturgruppe. Die statistische Auswertung ergab hier jedoch keine ausreichenden signifikanten Unterschiede zwischen den Vergleichsgruppen.A radomised emblinded study about the effect of acupuncture in the early days after implantation of a knee prosthesis. The results show a positive effect of the postoperative range of motion in the verumacupuncture group. Statistically was this diffence in between groups not signifikant

Genetical and biochemical characterisation of enzymes involved in the anaerobic monoterpene degradation in Castellaniella defragrans

Castellaniella defragrans is a betaproteobacterium metabolizing monoterpenes anaerobically under denitrifying conditions. Metabolite studies as well as a differential proteomic approach led to the identification of a linalool dehydratase-isomerase (ldi/LDI), a geraniol dehydrogenase (gedh/GeDH) and a candidate gene for a geranial dehydrogenase (gadh/GaDH). The LDI and GeDH were subjected to an initial biochemical characterization. In order to gain insight into the in vivo function of these genes a genetic system for C. defragrans was developed based on a suicide vector. After confirmation of the correct genetic background the physiological characaterization of the obtained deletionmutants verified the postulated degradation pathway for β-myrcene. Besides, the results disclosed another monoterpene degradation pathway as well as novel enzyme activities. In addition to the genetic and physiological characterization the enzymes were heterologously expressed in E. coli and biochemically studied. The bifunctionally LDI catalyzes enantiospecifically the hydration of β-myrcene to (S)-( )-linalool with an enantiomeric excess of > 95 % that is further isomerised to geraniol. Chemical modification of cysteine, histidine, aspartic and glutamic acid residues inhibited the enzyme activity. By the deletion of the ldi gene in C. defragrans a phenotype was caused that lost the ability of degrading the acyclic β-myrcene, but cyclic monoterpene degradation was not effected. A novel enzyme activity acting on (R,S)-(±)-linalool was observed, too. The heterologously expressed GeDH was purified to homogeneity and native PAGE in combination with an activity staining revealed the native conformation as dimer. With regards to their kinetic properties recombinant and wild type GeDH correlated well with a high affinity for geraniol. Due to the deletion of the gedh mutant strains revealed an impaired growth on monoterpenes suggesting the presence of further alcohol dehydrogenases acting on geraniol. The candidate gene for a geranial dehydrogenase, which was found to be induced by growth on monoterpenes, interceded specifically the oxidation of geranial. The cis-isomer was not converted. The formation of NAD was in a stoichiometric ratio. To our knowledge, both GeDH and GaDH are the first monoterpenoid specific dehydrogenases originating from a bacterium

Die genetische und biochemische Charakterisierung von Enzymen des anaeroben Monoterpen-Abbaus in Castellaniella defragrans

Castellaniella defragrans is a betaproteobacterium metabolizing monoterpenes anaerobically under denitrifying conditions. Metabolite studies as well as a differential proteomic approach led to the identification of a linalool dehydratase-isomerase (ldi/LDI), a geraniol dehydrogenase (gedh/GeDH) and a candidate gene for a geranial dehydrogenase (gadh/GaDH). The LDI and GeDH were subjected to an initial biochemical characterization. In order to gain insight into the in vivo function of these genes a genetic system for C. defragrans was developed based on a suicide vector. After confirmation of the correct genetic background the physiological characaterization of the obtained deletionmutants verified the postulated degradation pathway for β-myrcene. Besides, the results disclosed another monoterpene degradation pathway as well as novel enzyme activities. In addition to the genetic and physiological characterization the enzymes were heterologously expressed in E. coli and biochemically studied. The bifunctionally LDI catalyzes enantiospecifically the hydration of β-myrcene to (S)-( )-linalool with an enantiomeric excess of > 95 % that is further isomerised to geraniol. Chemical modification of cysteine, histidine, aspartic and glutamic acid residues inhibited the enzyme activity. By the deletion of the ldi gene in C. defragrans a phenotype was caused that lost the ability of degrading the acyclic β-myrcene, but cyclic monoterpene degradation was not effected. A novel enzyme activity acting on (R,S)-(±)-linalool was observed, too. The heterologously expressed GeDH was purified to homogeneity and native PAGE in combination with an activity staining revealed the native conformation as dimer. With regards to their kinetic properties recombinant and wild type GeDH correlated well with a high affinity for geraniol. Due to the deletion of the gedh mutant strains revealed an impaired growth on monoterpenes suggesting the presence of further alcohol dehydrogenases acting on geraniol. The candidate gene for a geranial dehydrogenase, which was found to be induced by growth on monoterpenes, interceded specifically the oxidation of geranial. The cis-isomer was not converted. The formation of NAD was in a stoichiometric ratio. To our knowledge, both GeDH and GaDH are the first monoterpenoid specific dehydrogenases originating from a bacterium

Physiology of deletion mutants in the anaerobic β-myrcene degradation pathway in <it>Castellaniella defragrans</it>

<p>Abstract</p> <p>Background</p> <p>Monoterpenes present a large and versatile group of unsaturated hydrocarbons of plant origin with widespread use in the fragrance as well as food industry. The anaerobic β-myrcene degradation pathway in <it>Castellaniella defragrans</it> strain 65Phen differs from well known aerobic, monooxygenase-containing pathways. The initial enzyme linalool dehydratase-isomerase <it>ldi</it>/LDI catalyzes the hydration of β-myrcene to (<it>S</it>)-(+)-linalool and its isomerization to geraniol. A high-affinity geraniol dehydrogenase <it>geoA</it>/GeDH and a geranial dehydrogenase <it>geoB</it>/GaDH contribute to the formation of geranic acid.</p> <p>A genetic system was for the first time applied for the betaproteobacterium to prove <it>in vivo</it> the relevance of the linalool dehydratase-isomerase and the geraniol dehydrogenase. In-frame deletion cassettes were introduced by conjugation and two homologous recombination events.</p> <p>Results</p> <p>Polar effects were absent in the in-frame deletion mutants <it>C. defragrans</it> Δ<it>ldi</it> and <it>C. defragrans</it> Δ<it>geoA</it>. The physiological characterization of the strains demonstrated a requirement of the linalool dehydratase-isomerase for growth on acyclic monoterpenes, but not on cyclic monoterpenes. The deletion of <it>geoA</it> resulted in a phenotype with hampered growth rate on monoterpenes as sole carbon and energy source as well as reduced biomass yields. Enzyme assays revealed the presence of a second geraniol dehydrogenase. The deletion mutants were <it>in trans</it> complemented with the broad-host range expression vector pBBR1MCS-4<it>ldi</it> and pBBR1MCS-2<it>geoA</it>, restoring in both cases the wild type phenotype.</p> <p>Conclusions</p> <p>In-frame deletion mutants of genes in the anaerobic β-myrcene degradation revealed novel insights in the <it>in vivo</it> function. The deletion of a high-affinity geraniol dehydrogenase hampered, but did not preclude growth on monoterpenes. A second geraniol dehydrogenase activity was present that contributes to the β-myrcene degradation pathway. Growth on cyclic monoterpenes independent of the initial enzyme LDI suggests the presence of a second enzyme system activating unsaturated hydrocarbons.</p