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Substrate Solution (substrate + solution)
Selected AbstractsDevelopment of a Rapid Single-Drop Analysis Biosensor for Screening of Phenanthrene in Water SamplesELECTROANALYSIS, Issue 20 2004Abstract Detection techniques for biosensors often require bulky instruments or cells that are not feasible for in-field analysis. Our single-drop cell design, optimized in this work, comprised a screen-printed three-electrode (SPE), strip in horizontal position onto which a volume of 100,,L of sample or substrate solution was placed to ensure electrical contact (complete circuit). Together with optimized linear sweep voltammetry (LSV), parameters for the detection of the enzyme alkaline phosphatase (AP), the system was applied to a biosensor for the analysis of polycyclic aromatic hydrocarbons (PAHs), in environmental samples. A limit of detection (LOD), of 0.15,ppb was achieved for a model system with an IC50 value of 0.885 ppb and a linear range (LR), of 0.2,10,ppb. Application of the single drop analysis (SDA), format to a PAH biosensor gave a LOD of 1.4,ppb for detection of phenanthrene with an IC50 value of 29.3,ppb and linear range of 2,100,ppb. Proof of concept is shown with spiked sample analysis of phenanthrene in matrices such as sea, river and tap water. [source] Speciation of Arsenic under Dynamic ConditionsENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 6 2008J. Ackermann Abstract In periodically flooded soils, reductive conditions can occur, which favor the dissolution of Fe (hydr)oxides. Fe (hydr)oxides such as goethite are important sorbents for arsenate (AsV), which is the dominant As species in soils under aerobic conditions. Hence, the dissolution of Fe (hydr)oxides under reductive conditions can result in the mobilization and reduction of AsV and, thus, in an increase in the bioavailability of arsenic. The temporal dynamics of these processes and possible re-sorption or precipitation of arsenite (AsIII) formed are poorly understood. Under controlled laboratory conditions, the temporal change in the redox potential and arsenic speciation with time after a simulated flooding event in a quartz-goethite organic matter substrate, spiked with AsV, was examined. During a period of 6,weeks, substrate solutions were sampled weekly using micro-suction cups and analyzed for pH, AsIII and AsV, Fe, Mn and P concentrations. Redox potentials and matric potentials were determined in situ in the substrate-bearing cylinders. The redox potential and the ratio between AsIII and AsV concentrations remained unchanged during the experiment without organic matter application. With organic matter applied, the redox potential decreased and the AsIII concentrations in the substrate solution increased while the total As concentrations in the substrate solution strongly decreased. An addition of goethite (1,g/kg) per se led to a decrease of the total As in the substrate solution (almost 50,%). In respect to the potential As availability for plants, and consequently, the transfer into the food chain, the results are difficult to evaluate. The lower the total As concentrations in the substrate solution, determined with decreasing redox potential, the least plant As uptake will occur. This effect may however be compensated by a shift of the molar P/AsV ratio in the solution in favor of AsV which is expected to increase the As uptake. [source] Stabilized and Immobilized Bacillus subtilis Arginase for the Biobased Production of Nitrogen-Containing ChemicalsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Abstract L -Ornithine could serve as an intermediate in the biobased production of 1,4-diaminobutane from L -arginine. Using the concept of biorefinery, L -arginine could become widely available from biomass waste streams via the nitrogen storage polypeptide cyanophycin. Selective hydrolysis of L -arginine to L -ornithine is difficult to perform chemically, therefore the stabilization and immobilization of Bacillus subtilis arginase (EC,3.5.3.1) was studied in a continuously stirred membrane reactor system. Initial pH of the substrate solution, addition of L -aspartic acid and reducing agents all appeared to have an effect on the operational stability of B. subtilis arginase. A remarkably good operational stability (total turnover number, TTN=1.13,108) at the pH of arginine free base (pH,11.0) was observed, which was further improved with the addition of sodium dithionite to the substrate solution (TTN>1,109). B. subtilis arginase was successfully immobilized on three commercially available epoxy-activated supports. Immobilization on Sepabeads EC-EP was most promising, resulting in a recovered activity of 75% and enhanced thermostability. In conclusion, the stabilization and immobilization of B. subtilis arginase has opened up possibilities for its application in the biobased production of nitrogen-containing chemicals as an alternative to the petrochemical production. [source] High-throughput enzyme kinetics using microarraysISRAEL JOURNAL OF CHEMISTRY, Issue 2 2007Guoxin Lu We report a microanalytical method to study enzyme kinetics. The technique involves immobilizing horseradish peroxidase on a poly-L-lysine (PLL)-coated glass slide in a microarray format, followed by applying substrate solution onto the enzyme microarray. Enzyme molecules are immobilized on the PLL-coated glass slide through electrostatic interactions, and no further modification of the enzyme or glass slide is needed. In situ detection of the products generated on the enzyme spots is made possible by monitoring the light intensity of each spot using a scientific-grade charged-coupled device (CCD). Reactions of substrate solutions of various types and concentrations can be carried out sequentially on one enzyme microarray. To account for the loss of enzyme from washing in between runs, a standard substrate solution is used for calibration. Substantially reduced amounts of substrate solution are consumed for each reaction on each enzyme spot. The Michaelis constant Km obtained by using this method is comparable to the result for homogeneous solutions. Absorbance detection allows universal monitoring, and no chemical modification of the substrate is needed. High-throughput studies of native enzyme kinetics for multiple enzymes are therefore possible in a simple, rapid, and low-cost manner. [source] Triphase Hydrogenation Reactions Utilizing Palladium-Immobilized Capillary Column Reactors and a Demonstration of Suitability for Large Scale SynthesisADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 15 2005Juta Kobayashi Abstract We have developed a practical and highly productive system for hydrogenation reactions utilizing capillary column reactors, which occupy less space than ordinary batch systems, are low cost and easy to handle, and show feasibility toward large-scale chemical synthesis. Palladium-containing micelles were immobilized onto the inner surface of the capillaries. Nine palladium-immobilized capillaries were assembled and connected to a T-shaped connector, and hydrogen and a substrate solution were fed to capillaries via the connector. Hydrogenation of 1-phenyl-1-cyclohexene (1) proceeded smoothly to give phenylcyclohexane in quantitative yield. The capillaries themselves occupy only ca. 0.4,mL and a high space-time yield has been achieved (124.3,mg/17,min/0.4,mL). In addition, leaching of palladium was not detected by ICP analysis after reactions. [source] Development of a silica monolith microbioreactor entrapping highly activated lipase and an experiment toward integration with chromatographic separation of chiral estersJOURNAL OF SEPARATION SCIENCE, JSS, Issue 17 2007Koei Kawakami Abstract Microbioreactors are effective for high-throughput production of expensive products from small amounts of substrates. Lipases are versatile enzymes for chiral syntheses, and are highly activated when immobilized in alkyl-substituted silicates by the sol,gel method. For practical application of sol,gel immobilized lipases to a flow system, a microbioreactor loaded with a macroporous silica monolith is well suited, because it can be easily integrated with a chromatographic separator for optical resolution. We attempted to develop a microbioreactor containing a silica monolith-immobilized lipase. A nonshrinkable silica monolith was first formed from a 4:1 mixture of methyltrimethoxysilane (MTMS) and tetramethoxysilane (TMOS). It was then coated with silica precipitates entrapping lipase, derived from a 4:1 mixture of n -butyltrimethoxysilane (BTMS) and TMOS. As a result, monolith treated with the BTMS-based silicate entrapping lipase exhibited approximately ten times higher activity than nontreated monolith-immobilized lipase derived from the MTMS-based silicate, in transesterification between glycidol and vinyl n -butyrate in isooctane. A commercially available chiral column was connected in series to the monolith microbioreactor, and a pulse of substrate solution was supplied at the inlet of the reactor. Successful resolution of the racemic ester produced was achieved in the chromatographic column. [source] Speciation of Arsenic under Dynamic ConditionsENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 6 2008J. Ackermann Abstract In periodically flooded soils, reductive conditions can occur, which favor the dissolution of Fe (hydr)oxides. Fe (hydr)oxides such as goethite are important sorbents for arsenate (AsV), which is the dominant As species in soils under aerobic conditions. Hence, the dissolution of Fe (hydr)oxides under reductive conditions can result in the mobilization and reduction of AsV and, thus, in an increase in the bioavailability of arsenic. The temporal dynamics of these processes and possible re-sorption or precipitation of arsenite (AsIII) formed are poorly understood. Under controlled laboratory conditions, the temporal change in the redox potential and arsenic speciation with time after a simulated flooding event in a quartz-goethite organic matter substrate, spiked with AsV, was examined. During a period of 6,weeks, substrate solutions were sampled weekly using micro-suction cups and analyzed for pH, AsIII and AsV, Fe, Mn and P concentrations. Redox potentials and matric potentials were determined in situ in the substrate-bearing cylinders. The redox potential and the ratio between AsIII and AsV concentrations remained unchanged during the experiment without organic matter application. With organic matter applied, the redox potential decreased and the AsIII concentrations in the substrate solution increased while the total As concentrations in the substrate solution strongly decreased. An addition of goethite (1,g/kg) per se led to a decrease of the total As in the substrate solution (almost 50,%). In respect to the potential As availability for plants, and consequently, the transfer into the food chain, the results are difficult to evaluate. The lower the total As concentrations in the substrate solution, determined with decreasing redox potential, the least plant As uptake will occur. This effect may however be compensated by a shift of the molar P/AsV ratio in the solution in favor of AsV which is expected to increase the As uptake. [source] High-throughput enzyme kinetics using microarraysISRAEL JOURNAL OF CHEMISTRY, Issue 2 2007Guoxin Lu We report a microanalytical method to study enzyme kinetics. The technique involves immobilizing horseradish peroxidase on a poly-L-lysine (PLL)-coated glass slide in a microarray format, followed by applying substrate solution onto the enzyme microarray. Enzyme molecules are immobilized on the PLL-coated glass slide through electrostatic interactions, and no further modification of the enzyme or glass slide is needed. In situ detection of the products generated on the enzyme spots is made possible by monitoring the light intensity of each spot using a scientific-grade charged-coupled device (CCD). Reactions of substrate solutions of various types and concentrations can be carried out sequentially on one enzyme microarray. To account for the loss of enzyme from washing in between runs, a standard substrate solution is used for calibration. Substantially reduced amounts of substrate solution are consumed for each reaction on each enzyme spot. The Michaelis constant Km obtained by using this method is comparable to the result for homogeneous solutions. Absorbance detection allows universal monitoring, and no chemical modification of the substrate is needed. High-throughput studies of native enzyme kinetics for multiple enzymes are therefore possible in a simple, rapid, and low-cost manner. [source] Microfluidic biolector,microfluidic bioprocess control in microtiter platesBIOTECHNOLOGY & BIOENGINEERING, Issue 3 2010Matthias Funke Abstract In industrial-scale biotechnological processes, the active control of the pH-value combined with the controlled feeding of substrate solutions (fed-batch) is the standard strategy to cultivate both prokaryotic and eukaryotic cells. On the contrary, for small-scale cultivations, much simpler batch experiments with no process control are performed. This lack of process control often hinders researchers to scale-up and scale-down fermentation experiments, because the microbial metabolism and thereby the growth and production kinetics drastically changes depending on the cultivation strategy applied. While small-scale batches are typically performed highly parallel and in high throughput, large-scale cultivations demand sophisticated equipment for process control which is in most cases costly and difficult to handle. Currently, there is no technical system on the market that realizes simple process control in high throughput. The novel concept of a microfermentation system described in this work combines a fiber-optic online-monitoring device for microtiter plates (MTPs),the BioLector technology,together with microfluidic control of cultivation processes in volumes below 1,mL. In the microfluidic chip, a micropump is integrated to realize distinct substrate flow rates during fed-batch cultivation in microscale. Hence, a cultivation system with several distinct advantages could be established: (1) high information output on a microscale; (2) many experiments can be performed in parallel and be automated using MTPs; (3) this system is user-friendly and can easily be transferred to a disposable single-use system. This article elucidates this new concept and illustrates applications in fermentations of Escherichia coli under pH-controlled and fed-batch conditions in shaken MTPs. Biotechnol. Bioeng. 2010;107: 497,505. © 2010 Wiley Periodicals, Inc. [source] | |||||||||||||