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Half-life Time (half-life + time)
Selected AbstractsKinetics of HBV DNA and HBsAg in acute hepatitis B patients with and without coinfection by other hepatitis virusesJOURNAL OF MEDICAL VIROLOGY, Issue 3 2003Vladimir P. Chulanov Abstract The kinetics of hepatitis B virus (HBV) and its surface antigen (HBsAg) during acute hepatitis has not yet been studied accurately in a representative number of patients. The influence of coinfecting hepatitis viruses during the acute phase of infection is not known. Three to four serum samples from 21 patients with acute HBV monoinfection and 27 with coinfection were taken at intervals of 6,10 days and analyzed for the number of HBV genome equivalents (ge) by real time polymerase chain reaction (PCR) and for HBsAg quantity using Laurell electrophoresis. Log HBV ge/ml decreased during the follow-up from 6.8,±,1.1 to 5.1,±,1.0 to 4.2,±,0.8 to 3.3,±,1.1 (mean,±,SD). The half-life times of HBV ge increased from 1.6 days at the beginning to 4 days at the end. HBsAg decreased much slower: from 38 to 23 to 12 to3.8 ,g/ml. Half-life time was around 8 days at the beginning and 5.7 days at the end, but 11 patients showed a rapid elimination of HBsAg and HBV DNA. Hepatitis C virus (HCV) coinfection did not change the kinetics of HBV ge and HBsAg significantly. A moderate but significant suppression of HBV ge levels was observed in hepatitis D virus (HDV) coinfected patients. HBsAg levels were, however, enhanced in this cohort. In conclusion, the data suggest that expression and elimination of HBV is in most patients with acute hepatitis B not altered by coinfecting hepatitis viruses. The initial decrease of HBV ge and HBsAg in serum appears to be caused by decay or non-specific removal in the absence of replacement. J. Med. Virol. 69:313,323, 2003. © 2003 Wiley-Liss, Inc. [source] Benzoylphenylurea residues in peppers and zucchinis grown in greenhouses: determination of decline times and pre-harvest intervals by modellingPEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 2 2004Trinidad López-López Abstract Residue levels and degradation rates of five benzoylphenylurea insecticides were studied in zucchinis and peppers grown in experimental greenhouses in Almería (Spain). Benzoylphenylurea residues were analyzed by HPLC using on-line post-elution photoirradiation with fluorescence detection. Mathematically defined decline curves were established by determining optimal relationships between benzoylphenylurea residues and time, using different models. The models that best fitted the experimental data were those of first-order for diflubenzuron, triflumuron, hexaflumuron and flufenoxuron in zucchini and RF first-order models for the five insecticides in peppers and for lufenuron in zucchini. Half-life times for the residues on the two vegetables were estimated from the optimal models. In order to guarantee safe consumption of the two vegetables, we have estimated suitable pre-harvest intervals complying with the maximum residue levels established by the Spanish Government. In all cases, such pre-harvest intervals were shorter than those specified by the manufacturers of commercial formulates. Experimental data for the five insecticides in peppers and for lufenuron in zucchini were also fitted to a first-order model. Even though this function was legitimized statistically, estimations of decline times (T/2) and pre-harvest intervals were quite different from those provided by the optimal model. Copyright © 2004 Society of Chemical Industry [source] Original article: Thermal and light degradation kinetics of anthocyanin extracts from mangosteen peel (Garcinia mangostana L.)INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2010Renan C. Chisté Summary The stability and half-life time of anthocyanin extracts from mangosteen peel were studied under controlled oxygen supply, undergoing the influence of light source (fluorescent, incandescent, infrared and ultraviolet) and storage temperature (5, 28, 40 and 50 °C). The kinetic parameters for anthocyanin degradation, under different illumination conditions fit the first-order reaction model, and the exposition under fluorescent light resulted in a higher half-life time (597 h), followed by incandescent (306 h), ultraviolet (177 h) and infrared (100 h). The kinetic behaviour for the storage in different temperatures also fit the first order, and at 5 °C the highest half-life time (4006 h) was found, followed by 28 °C (370 h), 40 °C (125 h) and 50 °C (93 h). The activation energy was 14.7 Kcal.mol,1, and Q10 values showed that at 5 °C the anthocyanin extracts were more sensitive to storage temperature changes compared to the other tested temperatures. [source] Influence of ferulic acid on stability of anthocyanins from Cabernet Sauvignon grapes in a model system and a yogurt systemINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 8 2007Eliana Fortes Gris Summary The influence of different factors on the stability of the anthocyanin crude extract from Cabernet Sauvignon grape skins was investigated. In a model system, the factors evaluated were as follows: temperature 4 ± 1 °C and 29 ± 3 °C, presence and absence of light, pH 3.0 and 4.0 and presence of ferulic acid. The influence of the addition of ferulic acid to anthocyanins was investigated in a yogurt system stored at 4 ± 1 °C. The results obtained for anthocyanin degradation velocity constant and for the half-life time of anthocyanins in a model system and in a yogurt system showed that ferulic acid significantly increased the stability of the anthocyanins crude extract. [source] Experimental determination of Anammox decay coefficientJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 8 2009D. Scaglione Abstract This paper describes an experimental method used to evaluate the anaerobic ammonium oxidation (Anammox) decay coefficient by means of a batch test. The test was carried out using an experimental procedure based on manometric measurements of the dinitrogen gas that is produced by the Anammox process. The accuracy of the procedure had previously been assessed, and the method was used to determine the specific Anammox activity (SAA mg N2 -N g VSS,1 d,1,) and the maximum nitrogen production rate (MNPR, NmL N2 L,1 d,1) under several different conditions. A specific batch test, which lasted for 148 days, was performed to assess the decay coefficient. The activity decrease was monitored and the estimated value of the decay coefficient was found to be 0.0048 d,1 at 35 °C, for which the corresponding half-life time of the Anammox biomass was 145 days. This value is higher than other values reported in the literature, but in accordance with the slow growth rate of the Anammox bacteria. Copyright © 2009 Society of Chemical Industry [source] Effect of temperature on pharmacokinetics of enrofloxacin in mud crab, Scylla serrata (Forsskål), following oral administrationJOURNAL OF FISH DISEASES, Issue 3 2008W H Fang Abstract The study was conducted to evaluate the pharmacokinetics of enrofloxacin following a single oral gavage (10 mg kg,1) in mud crab, Scylla serrata, at water temperatures of 19 and 26 °C. Enrofloxacin concentration in haemolymph was determined using high-performance liquid chromatography (HPLC). A multiple and repeated haemolymph sampling from the articular cavity of crab periopods was developed. The haemolymph of an individual crab was successfully sampled up to 11 times from the articular cavity. The profile of haemolymph enrofloxacin concentration of an individual crab versus time was thus achieved. The mean haemolymph enrofloxacin concentration versus time was described by a two-compartment model with first-order absorption at two water temperatures. The peak concentrations of haemolymph enrofloxacin at 19 and 26 °C were 7.26 and 11.03 ,g mL,1, at 6 and 2 h, respectively. The absorption and distribution half-life time ( and t1/2,) at 19 °C were 3.7 and 4.5 h, respectively, which were markedly larger than the corresponding values (1.1 and 1.5 h) at 26 °C; the elimination half-life time (t1/2,) was 79.1 and 56.5 h at 19 and 26 °C, respectively. The area under curve (AUC), total body clearance (Cl) and mean residence time (MRT0,,) at 19 °C were 636.0 mg L,1 h, 0.016 L h,1 kg,1 and 102.5 h, respectively; the corresponding values at 26 °C were 583.4 mg L,1 h, 0.018 L h,1 kg,1and 63.7 h. These results indicate that enrofloxacin is absorbed and eliminated more rapidly in mud crab at 26 °C than at 19 °C. [source] CLONING AND SEQUENCING OF THE ,-AMYLASE GENE FROM BACILLUS SUBTILIS US116 STRAIN ENCODING AN ENZYME CLOSELY IDENTICAL TO THAT FROM BACILLUS AMYLOLIQUEFACIENS BUT DISTINCT IN THERMAL STABILITYJOURNAL OF FOOD BIOCHEMISTRY, Issue 2 2010EZZEDINE BEN MESSAOUD ABSTRACT The gene encoding for the ,-amylase AMYUS116 was cloned and sequenced. The amino acid sequence of AMYUS116 exhibited an almost perfect homology with the ,-amylase BACAAM, excluding the residues N205 and N217 of AMYUS116 that were changed to H205 and I217 into BACAAM. Three mutant derivatives from AMYUS116 (N205H, N217I and N205H/N217I) were created by site-directed mutagenesis and their physicochemical and kinetic properties were compared with those of the wild-type enzymes. Therefore, the undertaken amylases mainly generated maltohexaose from starch and had radically the same kinetic parameters and optimum pH and temperature. They, however, were significantly distinct in thermal stability; AMYUS116 was more thermosensible as its half-life time at 80C was 13 min, while those of BACAAM and the double mutant were likewise 38 min. The single-mutant amylases exhibited an identically intermediate thermal stability as their half-life times at 80C were roughly 22 min. PRACTICAL APPLICATIONS Of particular interest to the current search is that the different thermal stability between AMYUS116 and BACAAM can lead to novel findings pertaining to protein stability, which can bring about new strategies for protein engineering. Basically, the comparative study of closely related amylases and the protein engineering of already existing ones are certainly important because they offer opportunities to understand the structure,function relationships of these biocatalysts. [source] KINETICS AND HYDROLYSIS PARAMETERS OF TOTAL FRUCTOOLIGOSACCHARIDES OF ONION BULBS: EFFECTS OF TEMPERATURE REGIMES AND CULTIVARSJOURNAL OF FOOD BIOCHEMISTRY, Issue 1 2007NOUREDDINE BENKEBLIA ABSTRACT This work studied the percentage of hydrolysis, observed hydrolysis rate constant (kobs), half-life time (t1/2) and kinetics of degradation of the total fructooligosaccharides (FOS) of three different onion bulb cultivars (Yellow Spanish, Red Amposta and Tenshin) kept during 6 months under three temperature regimes, 10, 15 and 20C. The percentage of hydrolysis of FOS was higher at 20C than at 10C and ranged from 47 to 58% at 10C, from 63 to 68% at 15C and from 74 to 83% at 20C. The kobs ranged from 27 × 10,3 to 36 × 10,3/week at 10C and from 41 × 10,3/week to 47 × 10,3/week at 15C, while at 20C, it was high and was about kobs 56 × 10,3/week.. The t1/2 decreased when temperature increased, and varied from 19.5 to 26.0 weeks at 10C, from 14.6 to 16.8 weeks at 15C and from 9.4 to 12.3 weeks at 20C, indicating that high degree of polymerization (DP) FOS have shorter lives than low DP FOS. Linear regression and kinetics of hydrolysis have shown that FOS hydrolysis is higher at 20C, with a coefficient of regression ranging between 0.87 and 0.99. Apparently, FOS hydrolysis is temperature independent, and storage time had more effect on the higher DP FOS than on the lower DP FOS. [source] Interfacial and foaming characteristics of milk whey protein and polysaccharide mixed systemsAICHE JOURNAL, Issue 4 2010Adrián A. Perez Abstract Protein-polysaccharide (PS) interactions find many applications in food engineering and new foam formulations. In this article, we have studied the effect of anionic nonsurface active PSs [sodium alginate (SA) and lambda-carrageenan (,-C)] in aqueous solution on interfacial and foaming characteristics of milk whey proteins [whey protein concentrate (WPC) and whey protein isolate (WPI)]. Whey protein concentration (1.0% wt), temperature (20°C), pH (7), and ionic strength (0.05 M) of the aqueous media were kept constant, while PS influence was evaluated within a 0.0,1.0% wt concentration range. The dynamic properties (dynamics of adsorption and surface dilatational properties) of WPC/PS and WPI/PS adsorbed films were considered in order to correlate the foaming characteristics of the biopolymer mixed systems. Foaming characteristics of the biopolymer mixed systems depended on the PS relative concentration in the aqueous phase and on the whey protein-PS interactions in solution and at the air,water interface. Dynamic surface properties of the adsorbed films at short adsorption time had a significant effect on foaming capacity. For a particular system, the overall foam destabilization (foam half-life time) and the individual destabilization processes (drainage, disproportionation, and bubble coalescence) depend on the nature of the PS, its relative bulk concentration, and whey protein-PS interactions in the vicinity of the air,water interface. The viscosity of the aqueous phase has an effect on the rate of drainage while the rate of disproportionation/collapse is more dependent on the interfacial characteristics of the adsorbed film. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Simultaneous reversible addition fragmentation chain transfer and ring-opening polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2008Maude Le Hellaye Abstract The simultaneous ring-opening polymerization (ROP) of ,-caprolactone (,-CL) and 2-hydroxyethyl methacrylate (HEMA) polymerization via reversible addition fragmentation chain transfer (RAFT) chemistry and the possible access to graft copolymers with degradable and nondegradable segments is investigated. HEMA and ,-CL are reacted in the presence of cyanoisopropyl dithiobenzoate (CPDB) and tin(II) 2-ethylhexanoate (Sn(Oct)2) under typical ROP conditions (T > 100 °C) using toluene as the solvent in order to lead to the graft copolymer PHEMA- g -PCL. Graft copolymer formation is evidenced by a combination of size-exclusion chromatography (SEC) and NMR analyses as well as confirmed by the hydrolysis of the PCL segments of the copolymer. With targeted copolymers containing at least 10% weight of PHEMA and relatively small PHEMA backbones (ca. 5,000,10,000 g mol,1) the copolymer grafting density is higher than 90%. The ratio of free HEMA-PCL homopolymer produced during the "one-step" process was found to depend on the HEMA concentration, as well as the half-life time of the radical initiator used. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3058,3067, 2008 [source] Insights into phase stability of anhydrous/hydrate systems: a Raman-based methodologyJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2010Mariela M. Nolasco Abstract FT-Raman spectroscopy turns out to be a powerful technique to evaluate the amount of polymorphic and pseudopolymorphic forms in crystalline samples,which is particularly relevant in pharmaceutical sciences. This paper presents a methodology that allows successful quantitative evaluation of the solid-state hydration and dehydration processes, using FT-Raman spectroscopy. All the steps required for a reliable evaluation of the hydration/dehydration process are illustrated for the caffeine system, a particularly challenging system presenting limited spectral differences between the pseudopolymorphs. The hydration process of caffeine was found to occur in a single-step process with a half-life time of ca 13 h, while the dehydration occurs through a two-step mechanism. The critical relative humidity was found to be at ca 81 and 42% for anhydrous and hydrate caffeine forms, respectively. Copyright © 2009 John Wiley & Sons, Ltd. [source] Pharmacokinetic parameters estimation using adaptive Bayesian P-splines modelsPHARMACEUTICAL STATISTICS: THE JOURNAL OF APPLIED STATISTICS IN THE PHARMACEUTICAL INDUSTRY, Issue 2 2009Astrid Jullion Abstract In preclinical and clinical experiments, pharmacokinetic (PK) studies are designed to analyse the evolution of drug concentration in plasma over time i.e. the PK profile. Some PK parameters are estimated in order to summarize the complete drug's kinetic profile: area under the curve (AUC), maximal concentration (Cmax), time at which the maximal concentration occurs (tmax) and half-life time (t1/2). Several methods have been proposed to estimate these PK parameters. A first method relies on interpolating between observed concentrations. The interpolation method is often chosen linear. This method is simple and fast. Another method relies on compartmental modelling. In this case, nonlinear methods are used to estimate parameters of a chosen compartmental model. This method provides generally good results. However, if the data are sparse and noisy, two difficulties can arise with this method. The first one is related to the choice of the suitable compartmental model given the small number of data available in preclinical experiment for instance. Second, nonlinear methods can fail to converge. Much work has been done recently to circumvent these problems (J. Pharmacokinet. Pharmacodyn. 2007; 34:229,249, Stat. Comput., to appear, Biometrical J., to appear, ESAIM P&S 2004; 8:115,131). In this paper, we propose a Bayesian nonparametric model based on P-splines. This method provides good PK parameters estimation, whatever be the number of available observations and the level of noise in the data. Simulations show that the proposed method provides better PK parameters estimations than the interpolation method, both in terms of bias and precision. The Bayesian nonparametric method provides also better AUC and t1/2 estimations than a correctly specified compartmental model, whereas this last method performs better in tmax and Cmax estimations. We extend the basic model to a hierarchical one that treats the case where we have concentrations from different subjects. We are then able to get individual PK parameter estimations. Finally, with Bayesian methods, we can get easily some uncertainty measures by obtaining credibility sets for each PK parameter. Copyright © 2008 John Wiley & Sons, Ltd. [source] Development of predictive quantitative retention,activity relationship models of alkaloids by mixed micellar liquid chromatographyBIOMEDICAL CHROMATOGRAPHY, Issue 2 2010Yu Chen Abstract The mixed micellar liquid chromatography is a mode that uses mixed micellar system of Brij35/SDS (85 : 15) as a mobile phase under adequate experimental conditions, can simulate the resting membrane potential and the conformation of the long hydrophilic polyoxyethylene chains remains unchanged. In this article, the applications of biopartitioning micellar chromatography, using mixed micellar system to describe and estimate bioactivities of alkaloids, has been focused. The BMCBrij35/SDS -QRAR models of half-life time, volume of distribution, plasma clearance and area under concentration,time curve were obtained using Brij35-SDS retention data. The aim is to take a look at the capability of the mixed micellar liquid chromatography model to describe and/or estimate the bioactivity of alkaloids. Copyright © 2009 John Wiley & Sons, Ltd. [source] Involvement of alanine 103 residue in kinetic and physicochemical properties of glucose isomerases from Streptomyces speciesBIOTECHNOLOGY JOURNAL, Issue 2 2007Mohamed Ali Borgi Abstract The Ala103 to Gly mutation, introduced within the glucose isomerase from Streptomyces sp. SK (SKGI) decreased its catalytic efficiency (kcat/Km) toward D -glucose from 7.1 to 3 mM,1 min,1. The reverse counterpart replacement Gly103Ala introduced into the glucose isomerase of Streptomyces olivochromogenes (SOGI) considerably improved its catalytic efficiency to be 6.7 instead of 3.2 mM,1 min,1. This later mutation also increased the half-life time of the enzyme from 70 to 95 min at 80°C and mainly modified its pH profile. These results provide evidence that the residue Ala103 plays an essential role in the kinetic and physicochemical properties of glucose isomerases from Streptomyces species. [source] Autocatalytic Enantiomerisation at the Crystal Surface in Deracemisation of Scalemic ConglomeratesCHEMISTRY - A EUROPEAN JOURNAL, Issue 39 2009Shengwei Wei Dr. Abstract Deracemisation of racemic or scalemic conglomerates of intrinsically chiral compounds appears to be a promising method of chiral resolution. By combining the established methods of asymmetric synthesis and the physical process of crystal growth, we were able to achieve a complete deracemisation (with 100,%,ee) of an asymmetric Mannich product conglomerate,vigorously stirred in its saturated solution,from a starting enantiomeric excess value of 15.8,% in the presence of pyrrolidine (8,mol,%) as an achiral catalyst for the CC bond-forming reaction. Strong activation of this deracemisation process was observed on mild isothermal heating to only 40,°C, resulting in dramatic acceleration by a factor of about 20 with respect to the results obtained at room temperature. Despite the fact that the racemisation half-life time of the nearly enantiopure Mannich product (with 99,%,ee) in the homogenous solution at the reaction temperature is eight days, the deracemisation process took only hours in a small-scale experiment. This apparent paradox is explained by a proposed rapid enantiomerisation at the crystal/solution interface, which was corroborated by a 13C labelling experiment that confirmed the involvement of rapid enantiomerisation. Frequent monitoring of the solution-phase ee of the slowly racemising compound further revealed that the minor enantiomer dominated in solution, supporting an explanation based on a kinetic model. A generalisation of the process of "aymmetric autocatalysis" (resulting in automultiplication of chiral products in homogenous media) to encompass heterogeneous systems is also suggested. [source] Activity and Stability of Hammerhead Ribozymes Containing 2,- C- Methyluridine: a New RNA MimicCHEMISTRY & BIODIVERSITY, Issue 2 2005Mariana Gallo We propose 2,- C -methylnucleotides as a new class of 2,-modified RNA mimics. These analogues are expected to provide 2,-OH groups capable of reproducing the interactions observed in natural RNA and, due to the presence of the Me group, to possess increased stability towards nucleases. In this work, we investigate the catalytic activity and nuclease resistance of hammerhead ribozymes carrying 2,- C -methyluridines in positions 4 and 7 of the catalytic core. We describe the in vitro activity of these chimeric molecules and their stability in cell lysate, fetal calf serum, and cell culture medium. The data show that, when only position 4 is modified, activity decreases twofold; while, when both 4 and 7 positions are substituted, a sevenfold drop in activity is observed. Regarding biological stability, the main increase of the half-life time is observed when position 7 is modified. These results suggest that 2,- C -methylnucleotides may be useful in the design of chemically synthesized RNA mimics with biological activity. [source] CLONING AND SEQUENCING OF THE ,-AMYLASE GENE FROM BACILLUS SUBTILIS US116 STRAIN ENCODING AN ENZYME CLOSELY IDENTICAL TO THAT FROM BACILLUS AMYLOLIQUEFACIENS BUT DISTINCT IN THERMAL STABILITYJOURNAL OF FOOD BIOCHEMISTRY, Issue 2 2010EZZEDINE BEN MESSAOUD ABSTRACT The gene encoding for the ,-amylase AMYUS116 was cloned and sequenced. The amino acid sequence of AMYUS116 exhibited an almost perfect homology with the ,-amylase BACAAM, excluding the residues N205 and N217 of AMYUS116 that were changed to H205 and I217 into BACAAM. Three mutant derivatives from AMYUS116 (N205H, N217I and N205H/N217I) were created by site-directed mutagenesis and their physicochemical and kinetic properties were compared with those of the wild-type enzymes. Therefore, the undertaken amylases mainly generated maltohexaose from starch and had radically the same kinetic parameters and optimum pH and temperature. They, however, were significantly distinct in thermal stability; AMYUS116 was more thermosensible as its half-life time at 80C was 13 min, while those of BACAAM and the double mutant were likewise 38 min. The single-mutant amylases exhibited an identically intermediate thermal stability as their half-life times at 80C were roughly 22 min. PRACTICAL APPLICATIONS Of particular interest to the current search is that the different thermal stability between AMYUS116 and BACAAM can lead to novel findings pertaining to protein stability, which can bring about new strategies for protein engineering. Basically, the comparative study of closely related amylases and the protein engineering of already existing ones are certainly important because they offer opportunities to understand the structure,function relationships of these biocatalysts. [source] Cp2TiCl-catalyzed living radical polymerization of styrene initiated from peroxidesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2006Alexandru D. Asandei Abstract The effects of the reaction conditions and nature of the initiator were investigated in the Cp2Ti(III)Cl-catalyzed living radical polymerization of styrene initiated by benzoyl peroxide (BPO), tert -butyl peroxide (TBPO), tert -butyl peroxybenzoate (TBPOB), dicumyl peroxide (CPO), and tert -butylperoxy 2-ethylhexyl carbonate (TBPOEHC). The reversible termination of the growing chains with Cp2Ti(III)Cl affords a linear dependence of molecular weight on conversion over a wide range of temperatures (60,120 °C) with an optimum in polydispersity (Mw/Mn < 1.2) for St/BPO/Cp2TiCl2/Zn = 100/1/3/6 at 60,90 °C. The similarity of the kinetic parameters from polymerizations initiated by peroxides with vastly different half-life times (t = 1 h, t = 543 h) and the minimum peroxide/Ti = 1/2 ratio required for a living process indicate that initiation occurs primarily by the redox reaction of the peroxide with Cp2Ti(III)Cl rather than peroxide thermal decomposition. This is consistent with one Ti equivalent consumed in the redox initiation and the second one utilized in the reversible termination of the growing chains. Qualitatively, based on the livingness of the process, these initiators ranked as BPO > TBPOB , TBPO > CPO > TBPOEHC. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1106,1116, 2006 [source] Operational concept for the improved synthesis of (R)-3,3'-furoin and related hydrophobic compounds with benzaldehyde lyaseBIOTECHNOLOGY JOURNAL, Issue 5 2006Marion B. Ansorge-Schumacher Dr. Abstract Biphasic reaction systems for enzyme catalysis are an elegant way to overcome limited solubility and stability of reactants and facilitate continuous processes. However, many synthetically useful enzymes are not stable in biphasic systems of water and organic solvent. The entrapment in polymer beads of polyvinyl alcohol has been shown to enable the stable operation of enzymes unstable in conventional biphasic reaction systems. We report the extension of this concept to continuous operation in a fluidised bed reactor. The enzyme benzaldehyde lyase was used for the continuous synthesis of enantiopure (R)-3,3'-furoin. The results show enhanced stability with half-life times under operation conditions of more than 100 h, as well as superior enzyme utilisation in terms of productivity. Furthermore, racemisation and oxidation of the product could be successfully prevented under the non-aqueous and inert reaction conditions. [source] | |||||||||||||||||||||||||