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Wageningen, Netherlands

Pukin A.V.,Wageningen University | Boeriu C.G.,Agrotechnology and Food Science Group | Boeriu C.G.,Aurel Vlaicu University | Scott E.L.,Wageningen University | And 2 more authors.
Journal of Molecular Catalysis B: Enzymatic | Year: 2010

The title compound was prepared enzymatically from l-lysine in an excellent yield and under buffer-free conditions. l-Lysine was oxidized by the action of l-lysine α-oxidase from Trichoderma viride followed by spontaneous oxidative decarboxylation of the intermediate 6-amino-2-oxocaproic acid in the reaction medium. l-Lysine α-oxidase was immobilized on an epoxy-activated solid support (Sepabeads EC-EP) and the activity of both solution-based and immobilized enzyme in this reaction was determined. © 2009 Elsevier B.V. All rights reserved. Source

Skrzeszewska P.J.,Wageningen University | Skrzeszewska P.J.,Dutch Polymer Institute | Jong L.N.,Wageningen University | De Wolf F.A.,Agrotechnology and Food Science Group | And 2 more authors.
Biomacromolecules | Year: 2011

In this article we study shape-memory behavior of hydrogels, formed by biodegradable and biocompatible recombinant telechelic polypeptides, with collagen-like end blocks and a random coil-like middle block. The programmed shape of these hydrogels was achieved by chemical cross-linking of lysine residues present in the random coil. This led to soft networks, which can be stretched up to 200% and "pinned" in a temporary shape by lowering the temperature and allowing the collagen-like end blocks to assemble into physical nodes. The deformed shape of the hydrogel can be maintained, at room temperature, for several days, or relaxed within a few minutes upon heating to 50 °C or higher. The presented hydrogels could return to their programmed shape even after several thermomechanical cycles, indicating that they remember the programmed shape. The kinetics of shape recovery at different temperatures was studied in more detail and analyzed using a mechanical model composed of two springs and a dashpot. © 2011 American Chemical Society. Source

Gonzalez M.E.,University of California at Davis | Barrett D.M.,University of California at Davis | McCarthy M.J.,University of California at Davis | Vergeldt F.J.,Wageningen University | And 3 more authors.
Journal of Food Science | Year: 2010

Proton nuclear magnetic resonance (1H-NMR) relaxometry was used to study the effects of high pressure and thermal processing on membrane permeability and cell compartmentalization, important components of plant tissue texture. High pressure treated onions were subjected to pressure levels from 20 to 200 MPa at 5 min hold time at initial temperatures of 5 and 20 °C. Thermally treated onions were exposed for 30 min at temperatures from 40 to 90 °C. Loss of membrane integrity was clearly shown by changes in transverse relaxation time (T2) of water at temperatures of 60 °C and above. Destabilization effects on membranes exposed to high pressure were observed at 200 MPa as indicated by T2 measurements and cryo-scanning electron microscopy (Cryo-SEM). T2 relaxation successfully discriminated different degrees of membrane damage based on the T2 shift of the vacuolar component. Analyses of the average water self-diffusion coefficient indicated less restricted diffusion after membrane rupture occurred in cases of severe thermal treatments. Milder processing treatments yielded lower average diffusion coefficients than the controls. 1H-NMR proved to be an effective method for quantification of cell membrane damage in onions and allowed for the comparison of different food processes based on their impact on tissue integrity. © 2010 Institute of Food Technologists®. Source

Langeveld J.W.A.,Biomass Research | Kalf R.,KEMA | Elbersen H.W.,Agrotechnology and Food Science Group
Biofuels, Bioproducts and Biorefining | Year: 2010

Development of bioenergy production in the Netherlands is lagging. This paper presents an inventory of problems met by new bioenergy chains and compares these to literature and to other countries. Theoretical frameworks suggest that five elements are crucial for successful bioenergy chain development: (i) availability of (proven) technology; (ii) access to information; (iii) access to feedstocks, financial means, and markets; (iv) locations for new installations; and (v) efficient lobby activities and public support. Nine bioenergy chains were interviewed. Problems that are reported relate to insufficient knowledge of new technological concepts, and of nuisances (noise, emission, odor, and other) caused during bioenergy production. Feedstock markets (wood, byproducts, waste) and product markets (heat, CO 2) are underdeveloped, while some chains are experiencing extra problems finding a suitable location or obtaining necessary permits. Problems related to insufficient public support are most relevant for bioenergy chains depending on tax exemptions (pure vegetation oil transportation fuels) or requiring adaptation of legislation (location permits for farm fermenters). An international comparison to barriers for biofuel suggests that economic factors (including lack of capital), limitations in know-how and institutional capacities, underdeveloped biomass and carbon markets, problems in chain coordination, and limited public support are largest problems for new bioenergy chains. Recommendations to stimulate bioenergy production in the Netherlands refer to performance standards for new installation types, information on feedstock availability, protocols for heat exchange and on improved credit facilities. © 2010 Society of Chemical Industry and John Wiley & Sons, Ltd. Source

Van Dinther A.M.C.,Agrotechnology and Food Science Group | Schroen C.G.P.H.,Agrotechnology and Food Science Group | Vergeldt F.J.,Laboratory of Biophysics | Van Der Sman R.G.M.,Agrotechnology and Food Science Group | And 2 more authors.
Advances in Colloid and Interface Science | Year: 2012

Microfluidic devices are an emerging technology for processing suspensions in e.g. medical applications, pharmaceutics and food. Compared to larger scales, particles will be more influenced by migration in microfluidic devices, and this may even be used to facilitate segregation and separation. In order to get most out of these completely new technologies, methods to experimentally measure (or compute) particle migration are needed to gain sufficient insights for rational design. However, the currently available methods only allow limited access to particle behaviour. In this review we compare experimental methods to investigate migration phenomena that can occur in microfluidic systems when operated with natural suspensions, having typical particle diameters of 0.1 to 10 μm. The methods are used to monitor concentration and velocity profiles of bidisperse and polydisperse suspensions, which are notoriously difficult to measure due to the small dimensions of channels and particles. Various methods have been proposed in literature: tomography, ultrasound, and optical analysis, and here we review and evaluate them on general dimensionless numbers related to process conditions and channel dimensions. Besides, eleven practical criteria chosen such that they can also be used for various applications, are used to evaluate the performance of the methods. We found that NMR and CSLM, although expensive, are the most promising techniques to investigate flowing suspensions in microfluidic devices, where one may be preferred over the other depending on the size, concentration and nature of the suspension, the dimensions of the channel, and the information that has to be obtained. The paper concludes with an outlook on future developments of measurement techniques. © 2012 Elsevier B.V. All rights reserved. Source

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