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Thermodynamic and kinetic aspects on water vs. organic solvent as reaction media in the enzyme-catalysed reduction of ketones

The stereoselective reduction of ketones catalysed by alcohol dehydrogenase from Thermoanaerobium brockii was studied in different reaction media, hexane at controlled water activities, hexane with 2.5% water (biphasic) and pure water. The reactions were studied in the temperature range from -1 to 50°C. Increasing the water activity from 0.53 to 0.97 increased the reaction rate 16-fold. The rate w

Logistics needs qualitative research – especially action research

This paper describes how qualitative research methods, particularly action research case studies, can contribute to further advance and develop logistics research. The paper also describes limitations with the current dominance of quantitative (especially survey) research in logistics. However, the paper is not a pure criticism of the use of quantitative research methods in general or in logistics

Stability and stabilization of hydroxynitrile lyase in organic solvents

The stability of hydroxynitrile lyase from Hevea brasiliensis has been studied in organic solvents. In dry solvents, the enzyme had half-lives in the range 1400-2500 hours. The enzyme half-life was one order of magnitude lower if the medium was water saturated. The substrates, aldehyde and hydrogen cyanide, were found to promote enzyme deactivation. The deactivation increased with substrate concen

Stabilisation of chloroperoxidase towards peroxide dependent inactivation

The addition of polyethyleneimine with a molecular weight of 2000 to chloroperoxidase from Caldariomyces fumago dramatically improved the stability of the enzyme towards peroxide dependent inactivation. The rate constant for the H 2 O 2 -dependent inactivation of chloroperoxidase decreased from 0.0016s -1 to 1.1 * 10 -5 s -1 in the presence of 1% polyethyleneimine. The stabilising effect towards

Lysophosphatidylcholine synthesis with Candida antarctica lipase B (Novozym 435)

Immobilized lipase from Candida antarctica lipase B (Novozym 435) was effective in the synthesis of lysophosphatidylcholine (LPC). The transesterification of L-α-glycerophosphorylcholine (GPC) and vinyl laurate was carried out in a solvent free system or in the presence of 50% (v/v) t- butanol. High conversions (>95%) were easily achieved. The lipase was selective for the sn-1 position of the glyc

Microbial production of D-(S)-chlorolactic acid by Proteus vulgaris cells

Hydroxy carboxylate viologen oxidoreductase (HVOR) contained in Proteus vulgaris cells was used in the reduction of chloropyruvic acid to D-(S)-chlorolactic acid. A synthetic electron mediator 1,1'-carbamoylmethylviologen (CAV) was used to transfer electrons to HVOR. Three different methods for regenerating the mediator were evaluated: (1) electrochemically driven reduction; (2) reduction driven

Mass transfer studies on immobilized α-chymotrypsin biocatalysts prepared by deposition for use in organic medium

Mass transfer limitations were studied in enzyme preparations of α- chymotrypsin made by deposition on different porous support materials such as controlled pore glasses, Celite, and polyamides of different particle sizes. It is the onset of mass transfer limitations that determines the position of the activity optimum with respect to enzyme loading on each support. The evidence of various experim

Triacylglycerols of Vernonia galamensis seed oil

Separation methods using silica gel column chromatography and preparative thin layer chromatography were employed to prepare pure triacylglycerol fractions of the oil from Vernonia galamensis seeds. Pure vernolic acid (12, 13-epoxy-octadec-cis-9-enoic acid) was prepared by enzymatic hydrolysis of the chromatographically purified major triacylglycerol, trivernolin, using a commercially available im

Characterization and optimization of phospholipase A2 catalyzed synthesis of phosphatidylcholine

The phospholipase A2 (PLA2) catalyzed synthesis and hydrolysis of phosphatidylcholine (PC) was studied in a water activity controlled organic medium. The aim of the study was to find the conditions most favorable for the synthetic reaction. To do this, the impact of various parameters such as water activity, substrate concentration and temperature on enzyme activity and equilibrium yield was deter

An agarose gel electrophoresis method for the separation of arabinogalactan proteins.

A method for resolving plasma membrane associated arabinogalactan proteins (AGPs) has been developed. Plasma membranes purified by aqueous polymer two‐phase partitioning were first subjected to Triton X‐114 fractionation. The resulting water phase contained all detectable plasma membrane‐bound AGPs. Plasma membrane AGPs were then resolved in an SDS‐agarose gel electrophoresis system (SDS‐AGE). For

Effects of human pancreatic lipase-colipase and carboxyl ester lipase on eicosapentaenoic and arachidonic acid ester bonds of triacylglycerols rich in fish oil fatty acids.

Fish oil chylomicrons, obtained from mesenteric duct chyle of rats fed [3H]20:5 and [14C]20:4 or [3H]20:5 and [14C]18:2 in a fish oil emulsion, were incubated with human pancreatic lipase-colipase, human carboxyl ester lipase (CEL) and human duodenal contents. With duodenal contents, the triacylglycerols labelled with [3H]20:5 and [14C]20:4 were rapidly converted to free fatty acids (FFA) and mono

Vehicle functionality - Why we need a structured development process

In the early days of vehicle engineering, the car was designed top-down. Most design decisions were taken bearing the complete vehicle in mind. As sub-systems have become more complex, and also deeply interlinked, the width of the problem has become impossible for one engineer to understand in all aspects. To be able to cope with this, vehicle manufacturers have created stable partitionings of the

Prospective Evaluation of Health After Breast Reduction Surgery Using the Breast-Q, Short-Form 36, Breast-Related Symptoms Questionnaire, and Modified Breast Evaluation Questionnaire

INTRODUCTION: Breast hypertrophy is a condition associated with physical, psychological, and psychosocial problems. The primary aims of this study were to determine the impact of breast hypertrophy and the effects of breast reduction, performed on the basis of well-described inclusion criteria, on general and breast-related health, using both general and diagnosis-specific validated questionnaires

Heavy-quark mass effects in Higgs plus jets production

We study the production of a Standard Model Higgs boson in the gluon-fusion channel at the 13 TeV LHC. Our results are accurate to the next-to-leading order in QCD, bar for the lack of some two-loop amplitudes, for up to two extra jets and are matched to the Pythia8 Monte Carlo. We address the impact, at the level of inclusive rates and of differential distributions, of the merging of samples char

Enhancing the ttH signal through top-quark spin polarization effects at the LHC

We consider the impact of the tt spin correlations in the Higgs boson production in association with top quark pairs pp→ttH and in the corresponding backgrounds. We study the H→bb and H→γγ decay modes. We show that retaining the tt spin-correlation effects could significantly improve the LHC sensitivity to the ttH signal, particularly in the H→γγ channel.