Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Characterization of apoptosis in PER.C6® batch and perfusion cultures
    Mercier, S.M. ; Diepenbroek, B. ; Martens, D.E. ; Wijffels, R.H. ; Streefland, M. - \ 2015
    Biotechnology and Bioengineering 112 (2015)3. - ISSN 0006-3592 - p. 569 - 578.
    hamster ovary cells - high-level expression - flow-cytometry - line per.c6 - death - adenovirus - dna - vaccine - gene - manufacture
    Preventing or delaying cell death is a challenge in mammalian cell cultures for the development and optimization of production processes for biopharmaceuticals. Cell cultures need to be maintained highly viable for extended times in order to reach maximum production yields. Moreover, programmed cell death through apoptosis is often believed to occur without being detected by classical viability measurements. In this study, we characterized cell death in PER.C6® batch and perfusion cultures using three flow cytometry techniques measuring different steps of the apoptosis cascade: DNA fragmentation, caspases activation and phosphatidylserine externalization. We showed that apoptosis is the main pathway of PER.C6® cell death in batch cultures after depletion of main carbon sources. In high cell density perfusion cultures fed at a constant specific perfusion rate, both high viability and very limited apoptosis were observed. When extending this perfusion process far beyond standard operations, cultures were exposed to suboptimal process conditions, which resulted in an increase of apoptotic cell death. Moreover, we showed that the reference viability measurement using trypan blue exclusion properly assesses the level of cell death in PER.C6® cultures. This study is a first step in understanding the mechanisms of PER.C6® cell death, which will be helpful to support applications of the cell line.
    Concurrent formation of furan-2,5-and furan-2,4-dicarboxylic acid: unexpected aspects of the Henkel reaction
    Thiyagarajan, S. ; Pukin, A. ; Haveren, J. van; Lutz, M. ; Es, D.S. van - \ 2013
    RSC Advances : An international journal to further the chemical sciences 3 (2013)36. - ISSN 2046-2069 - p. 15678 - 15686.
    chiral building-blocks - renewable resources - crystal-structure - glucose dehydration - terephthalic acid - biomass - conversion - manufacture - chemistry - products
    The concurrent formation of furan-2,5- and furan-2,4-dicarboxylic acid under solvent free conditions via a disproportionation reaction is described. By reacting potassium-2-furoate at 260 degrees C in the presence of 22 mol% of (Lewis acidic) catalysts like CdI2 or ZnCl2, potassium-2-furoate is disproportionated to furan and furandicarboxylic acids. Besides furan and furan-2,5-dicarboxylic acid (2,5-FDCA) as the main products, furan-2,4-dicarboxylic acid (2,4-FDCA) is also formed as a by-product. Experimental evidence has been obtained that, under the reaction conditions applied, 2,5-FDCA and 2,4-FDCA are formed by separate reaction pathways. Selectivity towards the different FDCA isomers is affected by the type of catalyst used. Single-crystal X-ray analysis shows that 2,4-FDCA has a more 'linear' character compared to 2,5-FDCA and hence is structurally more comparable to terephthalic acid (TA), making it an interesting monomer for synthetic polyesters.
    Fate of Listeria monocytogenes in Gouda microcheese: No growth, and substantial inactivation after extended ripening times
    Wemmenhove, E. ; Stampelou, I. ; Hooijdonk, A.C.M. van; Zwietering, M.H. ; Wells-Bennik, M.H.J. - \ 2013
    International Dairy Journal 32 (2013)2. - ISSN 0958-6946 - p. 192 - 198.
    cheddar cheese - inoculum size - lactic-acid - behavior - manufacture - inhibition - survival - storage - milk - ph
    This challenge study demonstrates that Listeria monocytogenes does not grow in Gouda cheese: during the first 8 weeks of ripening no growth was observed and between 8 and 52 weeks viable numbers declined significantly in a well-established Gouda microcheese system. Cheese milk was artificially contaminated just prior to addition of the starter culture. Three individual L. monocytogenes strains were used, including strains originating from cheese, a cheese plant environment and a reference strain. During curd formation, viable numbers of L. monocytogenes increased by 0.5 log cfu g-1, resulting from entrapment in the curd. No growth was observed during the first 8 weeks of ripening. A significant decline in the viable numbers of L. monocytogenes was observed in Gouda cheese that was ripened for longer than 8 weeks. Two factors that could possibly control the fate of L. monocytogenes in Gouda cheese were lactic acid and water activity.
    Risk assessment approaches to setting thermal processes in food manufacture
    Bean, D. ; Bourdichon, F. ; Bresnahan, D. ; Davies, A. ; Geeraerd, A. ; Jackson, T. ; Membré, J.M. ; Pourkomailian, B. ; Richardson, P. ; Stringer, M. ; Uyttendaele, M. ; Zwietering, M.H. - \ 2012
    Belgium : ILSI (ILSI Europe Report Series ) - 40
    voedselverwerking - fabricage - risicoschatting - warmtebehandeling - food processing - manufacture - risk assessment - heat treatment
    Structural features and properties of soluble products derived from Eucalyptus globulus hemicelluloses
    Gullon, P. ; González-Muñoz, M.J. ; Gool, M.P. van; Schols, H.A. ; Hirsch, J. ; Ebringerová, A. ; Parajo, J.C. - \ 2011
    Food Chemistry 127 (2011)4. - ISSN 0308-8146 - p. 1798 - 1807.
    xylo-oligosaccharides - in-vitro - autohydrolysis liquors - intestinal microbiota - wood - xylooligosaccharides - fermentability - fermentation - spectroscopy - manufacture
    Eucalyptus globulus wood samples were subjected to double hydrothermal processing to remove extractives in the first stage, and to cause the selective solubilisation of 4-O-methylglucuronoxylan in the second stage. The hemicellulose-derived products present in the liquors from the second hydrothermal stage (substituted xylooligosaccharides, denoted XOS) were refined by treatments with membranes and ion exchange. The purified XOS product was assayed for composition and characterised by HPLC-RI, HPAEC-PAD, HPSEC, MALDI-TOF-MS and NMR techniques. The results suggested the presence of neutral and acidic XOS with a degree of acetylation of about 0.6. The fermentability of the refined XOS product by faecal inocula was assessed by measuring both substrate consumption and formation of short-chain fatty acids.
    Brushes and proteins
    Bosker, W.T.E. - \ 2011
    Wageningen University. Promotor(en): Martien Cohen Stuart, co-promotor(en): Willem Norde. - [S.l.] : S.n. - ISBN 9789085859178 - 142
    biofilms - eiwitten - adsorptie - aangroeiwerende middelen - fabricage - biomaterialen - biofilms - proteins - adsorption - antifouling agents - manufacture - biomaterials

    Brushes and Proteins

    Wouter T. E. Bosker

    Protein adsorption at solid surfaces can be prevented by applying a polymer brush at the surface. A polymer brush consists of polymer chains end-grafted to the surface at such a grafting density that the polymer chains stretch out into the solution. This is schematically shown in figure 1.


    Fig. 1. Cartoons of a polymer brush. Two ways of preparation: (a) chemical grafting and (b) grafting through adsorption of block copolymers, for instance by Langmuir-Blodgett deposition (LB).

    The main parameters determining the protein resistance of a brush are the grafting density (σ), the chain length (N) and the solvent quality. The thickness of the brush is a function of these parameters: H ~ N σ1/3.

    This research is related to biofouling: 'the undesirable accumulation of proteins and cells at a surface', which starts by adsorption of proteins at the surface. Prevention of biofouling is of vital interest in medicine, where bacterial adhesion may cause severe infections on biomaterials used for implants. Treatment with antibiotics has hardly any effect. The only promising remedy against infections in this case is the prevention of a bacterial film. Because protein adsorption is the first step in this process, the research in this thesis is focused on prevention of protein adsorption by polymer brushes.

    Numerous studies over the past decades revealed that neutral polymer brushes, especially from poly(ethylene oxide) (PEO), can minimize protein adsorption. Mindful of the parameters determining the adsorbed amount mentioned above, the following three mechanisms can be identified, displayed in figure 2. Primary adsorption occurs when the diameter of the protein is (much) smaller than the distance between the polymer chains. In case of secondary adsorption, the protein is (much) bigger than the distance between the polymer chains. Ternary adsorption results from an attraction between the proteins and the polymer chains in the brush and was first discovered by Currie et al. In 1999. For a considerable time researchers have assumed a repulsion between the proteins and the polymer chains, thereby neglecting the possible ternary adsorption. However, there is increasing evidence that this attraction occurs, especially with PEO brushes. This is highlighted in this research, by adsorption studies at bimodal PEO brushes, consisting of a dense PEO brush of short chains with a varying PEO brush of long chains.

    Figure 2.
    Different mechanisms for protein adsorption at polymer brushes:

    primary, secondary and ternary adsorption.

    The main objective of this research was to investigate whether polysaccharide brushes, in particular dextran brushes, could be prepared at a solid surface and to study their protein repellency. It was suggested that brushes from these natural polymers would be more successful to prepare nonfouling surfaces with. Dextran brushes were prepared using Langmuir-Blodgett deposition (LB) and PS-dextran diblock copolymers, illustrated in figure 1. With the LB method it is possible to control both σ and N. The synthesis of the PS-dextran diblock copolymers is described in the thesis as well as the interfacial behavior. Quasi-2D aggregation occurred at the air-water interface during preparation (compression of the PS-dextran monolayer, see figure 1), resulting in inhomogeneous dextran layers at low grafting density. At higher grafting density these aggregates were pushed together to form a homogeneous dextran brush, as illustrated by AFM images. This transition from inhomogeneous to homogeneous results in non-continuous adsorption behavior at dextran brushes, in contrast to PEO brushes, as demonstrated in figure 3.


    Figure 3. Normalized adsorption of BSA (Γ/ Γ0) at dextran brushes (■) and PEO brushes (○).

    In case of dextran brushes the adsorption of BSA is constant up to a specific σ, followed by a drastic decrease, while PEO brushes show a gradual reduction.Figure 3 also demonstrates that dextran brushes are as efficient as PEO brushes in preventing protein adsorption, at high σ. This is the main conclusion of this research. It is expected that at even higher σ dextran brushes will completely suppress protein adsorption.

    Reconsidering the importance of interfacial properties in foam stability
    Wierenga, P.A. ; Norel, L. van; Basheva, E.S. - \ 2009
    Colloids and Surfaces. A: Physicochemical and Engineering Aspects 344 (2009)1-3. - ISSN 0927-7757 - p. 72 - 78.
    bovine beta-lactoglobulin - maillard reaction - whey proteins - soap films - egg-white - ovalbumin - behavior - manufacture - emulsions - glycation
    In food industry, protein isolates are often used to help in the formation and stabilisation of food foams. Subsequently there is great interest in (1) understanding the effect of processing parameters on the functional properties of the isolate, and (2) methods and techniques that can help to predict the foam properties. This article describes the foaming properties of proteins that were modified in the Maillard reaction. From these relatively simple experiments results were obtained that indicate that for certain protein solutions the foam properties can vary significantly, while the interfacial properties are constant. Commercial protein isolates originate from only a few sources, mainly egg white and whey, and sometimes plant proteins (e.g. soy). Despite these limited sources a large variety of isolates with a wide range of properties is produced. One source of variation is the isolation procedure, but at least equally important are the conditions used before, during and after drying the protein solution to form the dry powder. From the literature it was found that one of the major changes to the protein during processing of the isolates is the covalent coupling of sugars via the Maillard reaction. To study the effects of these reactions, a model system was produced that consists of proteins that were glycated to different degrees using Maillard reaction. For each sample, interfacial properties (e.g. surface pressure, dilatational modulus) were determined, and foam experiments were performed. The results show that at constant concentration of both the protein (0.5 g/L) and sugar (0.7 g/L), the foam-ability and stability could be significantly improved (e.g. non-modified lysozyme does not foam, the highest modification is easily foamed and the foam has a half-life time of 200 s). Interestingly, the improved foam properties could not be related to any change in interfacial properties. While foam stability improved with increasing modification, the measured interfacial properties were not significantly affected. These observations seem to go against the general view that changes in foam behaviour should be reflected in changes in the interfacial properties. Additional experiments on thin liquid films were performed, where the disjoining isotherm was measured. These isotherms did not show significant differences in the interactions between the adsorbed layers. This indicates that the electrostatic and steric interactions between the adsorbed layers do not depend on the degree of modification. Only the thin film stability against rupture was found to increase with increasing modification. The thin film experiments lead to the hypothesis that aggregates (or oligomeric proteins) formed during modification might become trapped in the film. The presence of these oligomeric proteins could result in an increase of the apparent viscosity in these films, or in gelling or jamming of the liquid phase between the two interfaces. In other words, the observed behaviour is the result of the confined geometry of the thin films. The results confirm other observations that Maillard reactions improve foaming properties. Moreover, strong indications were found that to predict foam stability we need more than the traditional parameters (i.e. (dynamic) surface pressure, interfacial reology, and disjoining pressure).
    Coir based building and packaging materials : final report of project CFC/FIGHF/11
    Snijder, M.H.B. ; Keijsers, E.R.P. ; Oever, M.J.A. van den; Dam, J.E.G. van - \ 2006
    Wageningen : Agrotechnology & Food Innovations (Report / Wageningen UR, Agrotechnology & Food Innovations 592) - ISBN 9789067549943 - 121
    kokosvezel - plantenvezels - bouwmaterialen - verpakkingsmaterialen - chemische samenstelling - lignine - fabricage - proefprojecten - haalbaarheidsstudies - ontwikkelingslanden - biobased economy - coir - plant fibres - building materials - packaging materials - chemical composition - lignin - manufacture - pilot projects - feasibility studies - developing countries - biobased economy
    Elucidating the relationship between the spreading coefficient, surface-mediated partial coalescence and the whipping time of artificial cream
    Hotrum, N.E. ; Cohen Stuart, M.A. ; Vliet, T. van; Avino, S.F. ; Aken, G.A. van - \ 2005
    Colloids and Surfaces. A: Physicochemical and Engineering Aspects 260 (2005)1-3. - ISSN 0927-7757 - p. 71 - 78.
    in-water emulsions - air/water interface - dairy emulsions - oil droplets - destabilization - manufacture - stability
    We studied the whipping of artificial creams composed of a blend of sunflower oil and hydrogenated palm fat stabilized by protein or a mixture or protein and low molecular weight (lmw) surfactant. It was found that an increased whipping speed, decreased protein concentration, and the addition of lmw surfactant leads to shorter whipping times. Further, shorter whipping times were observed for WPI-stabilized cream compared to cream stabilized by sodium caseinate. In all cases, the decrease in whipping time was due to a decrease in the length of the second stage of whipping, the stage characterized by the adhesion of fat droplets to the air bubble surface. The decrease in whipping time could be accounted for by considering the influence of the experimental variables on the fraction of bubble surface area at which fat droplet spreading is possible. The same changes in parameters that promote droplet spreading at the air/water interface cause a decrease in the whipping time of our model creams. Correlating the whipping time of cream with the spreading behavior of fat droplets at the air/water interface represents a new insight into the mechanisms involved in the whipping of cream.
    Daling transvetzuren, maar niet in alle grootverbruikproducten: vetzuursamenstelling van spijsvetten, koek en snacks.
    Hulshof, P.J.M. ; Zock, P.L. ; Kosmeijer-Schuil, J.G. ; Bovenkamp, P. van de; Katan, M.B. - \ 1998
    Voeding 59 (1998)5. - ISSN 0042-7926 - p. 24 - 27.
    vetzuren - carbonzuren - vetten - oliën - bakoliën - bakvetten - zoetwaren - biscuits - fabricage - cakes - snacks - maaltijden - voedingsmiddelen - chemische samenstelling - voeding - oleïnezuur - onverzadigde vetzuren - acrylzuur - volksgezondheid - gezondheidszorg - spijsoliën - spijsvetten - fatty acids - carboxylic acids - fats - oils - cooking oils - cooking fats - confectionery - biscuits - manufacture - cakes - snacks - meals - foods - chemical composition - nutrition - oleic acid - unsaturated fatty acids - acrylic acid - public health - health care - edible oils - edible fats
    Deze vetzuren hebben een ongunstige invloed op het lipoproteineprofiel in het bloed. In een tabel is de vetzuursamenstelling van geselecteerde koek en snacks weergegeven. Tegenwoordig bevatten de margarines, bak- en braadvetten aanzienlijk minder verzadigd vet
    Mechanical properties of short doughs and their corresponding biscuits
    Baltsavias, A. - \ 1996
    Agricultural University. Promotor(en): P. Walstra; T. van Vliet. - S.l. : Baltsavias - ISBN 9789054856092 - 159
    zoetwaren - biscuits - fabricage - cakes - bakkwaliteit - deeg - confectionery - biscuits - manufacture - cakes - baking quality - doughs

    The mechanical properties of short doughs of various composition were determined in small amplitude oscillatory experiments and in uniaxial compression. Regardless of composition, the linear region was very limited; beyond that, pronounced yielding and flow occurred. Conductimetry was also used to evaluate the effect of fat type and fat content on dough structure. Short doughs showed large differences in mechanical spectra, conductivity and apparent biaxial extensional viscosity, according to fat and sucrose contents, fat type and mixing time. It is concluded that short doughs are bicontinuous systems; reducing the fat content or changing the rheological properties of the fat relative to those of the non-fat phase results in fat-dispersed systems. The rheological properties of the non-fat phase are largely determined by intact flour particles present in a concentrated sucrose syrup. Sucrose delays, if not inhibits, gluten development through its effect on solvent quality and facilitates formation of a non-fat continuous phase via its effect on solvent quantity. Mixing promotes formation of a continuous fat phase.

    Mechanical properties of short-dough biscuits of various composition were determined in three-point bending tests. Increasing fat content or omitting sucrose from the recipe decreased the modulus and the fracture stress of the biscuits. The effect of fat content, however, was dependent on fat type. Temperature during dough preparation, dough water content and temperature during bending tests affected the mechanical properties of biscuits to an extent which depended on fat content. Diffusion of Sudan III into the biscuits indicated that low-fat biscuits are fat-dispersed systems and high-fat biscuits are bicontinuous. Differential scanning calorimetry showed that, irrespective of composition, starch gelatinisation was slight, if not absent, presumably due to the limited water content coupled with the low baking temperature. Under certain storage conditions, biscuits are in a glassy state. Upon water uptake, the matrix undergoes a glass-rubber transition. It is concluded that the mechanical properties of biscuits are mainly determined by air volume fraction, fat continuity, size of inhomogeneities, and physical state of the non-fat phase.

    Meten van klimaat in varkensstallen
    Werkgroep Meten van klimaat in varkensstallen, - \ 1991
    Rosmalen : Proefstation voor de Varkenshouderij (Proefverslag / Proefstation voor de Varkenshouderij P1.68) - 71
    gebouwen - constructie - milieubeheersing - verwarming - vochtigheid - instrumentatie - instrumenten (meters) - verlichting - fabricage - meting - varkensstallen - ventilatie - buildings - construction - environmental control - heating - humidity - instrumentation - instruments - lighting - manufacture - measurement - pig housing - ventilation
    Onderzoek GRAIN MINI V graanvochtmeter
    Anonymous, - \ 1988
    Wageningen etc. : Instituut voor Mechanisatie, Arbeid en Gebouwen [etc.] (IMAG bulletin no. 1085) - 8
    constructie - elevatoren - voer - graan - instrumentatie - instrumenten (meters) - fabricage - meting - silo's - vloeibare voedering - construction - elevators - feeds - grain - instrumentation - instruments - manufacture - measurement - silos - liquid feeding
    De dynamiek van het grondgebruik : een literatuurstudie
    Luijt, J. ; Bethe, F. - \ 1988
    Den Haag : L.E.I. (Onderzoekverslag / Landbouw-Economisch Instituut nr. 43) - 216
    landgebruik - economie - landbouwgrond - ruimtelijke ordening - zonering - overheidsbeleid - grondbeleid - landgebruiksplanning - milieu - landbouw - industrie - fabricage - nederland - overzichten - grondverzet - land use - economics - agricultural land - physical planning - zoning - government policy - land policy - land use planning - environment - agriculture - industry - manufacture - netherlands - reviews - earth moving
    Deze literatuurstudie beoogt theorieen te inventariseren en te beoordelen, die een verklaring kunnen geven van veranderingen van het grondgebruik in het landelijk gebied
    Marktverkenning verkeersregistratie - apparatuur
    Heijden, T.G.C. van der - \ 1987
    Wageningen : ICW (Nota / Instituut voor Cultuurtechniek en Waterhuishouding 1777) - 27
    constructie - tellen - dichtheid - instrumentatie - instrumenten (meters) - fabricage - meting - wegtransport - verkeer - construction - counting - density - instrumentation - instruments - manufacture - measurement - road transport - traffic
    Bepaling van het vocht- en vetgehalte in o.a. toast, crackers en knäckebröd m.b.v. NIR
    Oostenbrink, T.E. ; Coors, R.G. ; Frankhuizen, R. ; Veen, N.G. van der - \ 1985
    Wageningen : RIKILT (Rapport / RIKILT 85.123) - 4
    zoetwaren - biscuits - fabricage - cakes - voedingsmiddelen - voedselkwaliteit - kwaliteitscontroles - organische verbindingen - vochtgehalte - bepaling - samenstelling - verontreinigingen - analyse - infraroodspectroscopie - voedsel - vetten - confectionery - biscuits - manufacture - cakes - foods - food quality - quality controls - organic compounds - moisture content - determination - composition - impurities - analysis - infrared spectroscopy - food - fats
    Nagegaan is of met de Infra Alyzer-500 de gehalten aan vocht en vet in o. a. toast, crackers en knäckebröd voldoende nauwkeurig vast te stellen zijn.
    Prognose van de ontwikkeling van de landbouwmechanisatie en de landbouwwerktuigenindustrie in Mali gedurende de periode 1983-2000
    Moens, A. ; Wanders, A.A. - \ 1984
    Landbouwhogeschool Wageningen
    agricultural engineering - industry - crafts - manufacture - farm equipment - farm machinery - prognosis - production - construction - mali
    Landbouw en economie in Friesland : een analyse van de uitstralingseffecten van de Friese landbouw op de provinciale bedrijvigheid
    Dekker, K.M. ; Langevelde, A.P. van; Welle, J. ter - \ 1983
    Leeuwarden : Economisch-Technologisch Instituut voor Friesland [etc.] (Rapport / Economisch-Technologisch Instituut voor Friesland, Landbouw-Economisch Instituut no. 882) - 79
    landbouw - economische sectoren - industrie - fabricage - nederland - landbouw als bedrijfstak - friesland - agriculture - economic sectors - industry - manufacture - netherlands - agriculture as branch of economy - friesland
    Landbouwmechanisatie en landbouwwerktuigenindustrie in Mali : chronologische verslag van een bezoek aan een aantal instellingen en industrieen in Mali, Senegal, Ivoorkust, Frankrijk en Belgie in de periode december 1982/januari 1983
    Moens, A. ; Wanders, A.A. - \ 1983
    Wageningen : L.H. - 32
    landbouwtechniek - industrie - kunstnijverheid - fabricage - boerderij uitrusting - landbouwwerktuigen - mali - agrarische bedrijfsvoering - productie - constructie - agricultural engineering - industry - crafts - manufacture - farm equipment - farm machinery - mali - farm management - production - construction
    Parels en het kweken hiervan = Pearls and their culture
    Anonymous, - \ 1982
    Wageningen : Pudoc (Literatuurlijst / Centrum voor Landbouwpublikaties en Landbouwdocumentatie no. 4586)
    bibliografieën - goud - fabricage - oesterteelt - oesters - zilver - voorwerpen - bibliographies - gold - manufacture - oyster culture - oysters - silver - objects
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