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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    A cross sectional study on Dutch layer farms to investigate the prevalence and potential risk factors for different Chlamydia species
    Heijne, Marloes ; Goot, Jeanet A. van der; Fijten, Helmi ; Giessen, Joke W. van der; Kuijt, Eric ; Maassen, Catharina B.M. ; Roon, Annika van; Wit, Ben ; Koets, Ad P. ; Roest, Hendrik I.J. - \ 2018
    PLoS ONE 13 (2018)1. - ISSN 1932-6203
    In poultry several Chlamydia species have been detected, but Chlamydia psittaci and Chlamydia gallinacea appear to be most prevalent and important. Chlamydia psittaci is a well-known zoonosis and is considered to be a pathogen of poultry. Chlamydia gallinacea has been described more recently. Its avian pathogenicity and zoonotic potential have to be further elucidated. Within the Netherlands no data were available on the presence of Chlamydia on poultry farms. As part of a surveillance programme for zoonotic pathogens in farm animals, we investigated pooled faecal samples from 151 randomly selected layer farms. On a voluntary base, 69 farmers, family members or farm workers from these 151 farms submitted a throat swab. All samples were tested with a generic 23S Chlamydiaceae PCR followed by a species specific PCR for C. avium, C. gallinacea and C. psittaci. C. avium and psittaci DNA was not detected at any of the farms. At 71 farms the positive result could be confirmed as C. gallinacea. Variables significantly associated with the presence of C. gallinacea in a final multivariable model were ‘age of hens,’ ‘use of bedding material’ and ‘the presence of horses.’ The presence of C. gallinacea was associated with neither clinical signs, varying from respiratory symptoms, nasal and ocular discharges to diarrhoea, nor with a higher mortality rate the day before the visit. All throat swabs from farmers, family members or farm workers tested negative for Chlamydia DNA, giving no further indication for possible bird-to-human (or human-to-bird) transmission.
    Animal health risk of legally imported exotic animals into The Netherlands
    Vos-de Jong, C.J. de; Swanenburg, M. ; Tafro, N. ; Roon, A. van; Stenvers, Olaf F.J. ; Elbers, A.R.W. - \ 2017
    Animal health risk of legally imported exotic animals into the Netherlands in the period 2013-2014
    Vos-de Jong, Clazien de; Swanenburg, Manon ; Tafro, Nedzib ; Roon, Annika van; Stenvers, Olaf F.J. ; Elbers, Armin R.W. - \ 2017
    Microbial Risk Analysis 6 (2017). - ISSN 2352-3522 - p. 9 - 20.
    Animal health - Introduction risk - Legal import - Livestock health - Risk assessment - Wildlife trade
    The worldwide trade in exotic animals is a potential moderator for the global dispersion of infectious disease agents. Better insight into the pathogens that could be introduced by these trade flows can help to target surveillance efforts. The aim of this study was to evaluate the animal health risk for the Dutch livestock sector associated with the legal importation of exotic mammals, birds, reptiles, and amphibians originating from third countries (i.e. non-European Union member states). An inventory was made of exotic animals that were legally shipped to the Netherlands in the period 2013-2014 classified according to taxonomy and geographic origin, the results of which were used to assess the associated animal health risk. In this period, a total of 2.1 ×105 exotic animals were imported into the Netherlands from 25 different countries. The majority of these animals were reptiles (94%), whereas birds and mammals constituted < 1% of all imports. Trade figures were linked with information on worldwide occurrence of diseases and susceptibility of imported species to diseases to identify those exotic diseases that could potentially be introduced by these trade flows. This resulted in a selection of nine diseases for which the animal health risk due to the legal importation of exotic animals was assessed semi-quantitatively using proxy variables to score the probability of introduction and the expected impact of disease. The estimated introduction risk for the selected diseases varied from very low to moderate. Whereas importation of exotic animals might result in introduction of some diseases, the expected consequences for the livestock sector are expected to be limited. The diseases with the highest risk score were salmonellosis (exotic strains) and infection with Salmonella arizonae. Furthermore, the arboviral diseases Japanese encephalitis, Eastern equine encephalitis, and Western equine encephalitis might pose a risk due to the potential role of reptiles and amphibians as reservoir hosts for these diseases and the large numbers of these animals being imported by the Netherlands.
    Animal health risk of legally imported exotic animal into the Netherlands
    Vos, C. De; Nedzib, T. ; Roon, A. van; Stenvers, O. ; Elbers, A.R.W. ; Swanenburg, M. - \ 2016
    - p. 60 - 60.
    Public and animal health risk of import and transit of live exotic animals into the Netherlands in the period 2013 and 2014
    Roon, A. van; Maas, M. ; Toale, D. ; Giessen, J. van der; Vos-de Jong, C.J. de; Swanenburg, M. ; Tafro, N. - \ 2015
    Central Veterinary Institute of Wageningen UR (Report / CVI 15/CVI0318) - 147 p.
    Loss of Olfactory Function and Nutritional Status in Vital Older Adults and Geriatric Patients
    Toussaint, N. ; Roon, M. de; Campen, J.P.C.M. van; Kremer, S. ; Boesveldt, S. - \ 2015
    Chemical Senses 40 (2015)3. - ISSN 0379-864X - p. 197 - 203.
    mild cognitive impairment - odor identification - normative data - taste - malnutrition - smell - discrimination - dysfunction - prevalence - validation
    The aim of this cross-sectional study was to assess the association of olfactory function and nutritional status in vital older adults and geriatric patients. Three hundred forty-five vital (mean age 67.1 years) and 138 geriatric older adults (mean age 80.9 years) were included. Nutritional status was assessed using the mini nutritional assessment-short form. The Sniffin’ Sticks was used to measure olfactory function. Eleven percentage of the vital older adults were at risk of malnutrition, whereas 60% of the geriatric participants were malnourished or at risk. Only 2% of the vital older adults were anosmic, compared with 46% of the geriatric participants. Linear regression demonstrated a significant association (P = 0.015) between olfactory function and nutritional status in the geriatric subjects. However, this association became insignificant after adjustment for confounders. Both crude and adjusted analysis in the vital older adults did not show a significant association. The results indicate that, in both groups of elderly, there is no direct relation between olfactory function and nutritional status. We suggest that a decline in olfactory function may still be considered as one of the risk-factors for malnutrition in geriatric patients—once co-occurring with other mental and/or physical problems that are more likely to occur in those patients experience.
    Significant increase of Echinococcus multilocularis prevalencein foxes, but no increased predicted risk for humans
    Maas, M. ; Dam-Deisz, W.D.C. ; Roon, A.M. van; Takumi, K. ; Giessen, J.W.B. van der - \ 2014
    Veterinary Parasitology 206 (2014)3-4. - ISSN 0304-4017 - p. 167 - 172.
    human alveolar echinococcosis - red foxes - netherlands - transmission - switzerland - city - dogs
    The emergence of the zoonotic tapeworm Echinococcus multilocularis, causative agent ofalveolar echinococcosis (AE), poses a public health risk. A previously designed risk mapmodel predicted a spread of E. multilocularis and increasing numbers of alveolar echinococ-cosis patients in the province of Limburg, The Netherlands. This study was designed todetermine trends in the prevalence and worm burden of E. multilocularis in foxes in a popu-lar recreational area in the southern part of Limburg to assess the risk of infection for humansand to study the prevalence of E. multilocularis in dogs in the adjacent city of Maastricht.Thirty-seven hunted red foxes were tested by the intestinal scraping technique and nestedPCR on colon content. Additionally, 142 fecal samples of domestic dogs from Maastrichtwere analyzed by qPCR for the presence of E. multilocularis.In foxes, a significantly increased prevalence of 59% (95% confidence interval 43–74%)was found, compared to the prevalence of 11% (95% CI 7–18%) in 2005–2006. Average wormburden increased to 37 worms per fox, the highest since the first detection, but consistentwith the prediction about the parasite population for this region. Updated prediction onthe number of AE cases did not lead to an increase in previous estimates of human AE casesup to 2018. No dogs in the city of Maastricht tested positive, but results of questionnairesshowed that deworming schemes were inadequate, especially in dogs that were consideredat risk for infection.
    Vatbaarheid van Nerine voor PlAMV : voortgezet diagnostisch onderzoek 2013
    Leeuwen, P.J. van; Lemmers, M.E.C. ; Trompert, J.P.T. - \ 2014
    Lisse : Praktijkonderzoek Plant & Omgeving, Business Unit Bloembollen, Boomkwekerij en Fruit - 13
    nerine - bloembollen - plantenvirussen - plantago asiatica mosaic virus - virusziekten - diagnostische technieken - proeven - landbouwkundig onderzoek - nerine - ornamental bulbs - plant viruses - plantago asiatica mosaic virus - viral diseases - diagnostic techniques - trials - agricultural research
    Nerine blijkt niet vatbaar te zijn voor het PlAMV-virus. Het onderzoek naar de vatbaarheid van Nerine geeft dan ook geen aanleiding om de bestaande teeltstrategie aan te passen. Nerine wordt veelal in vruchtwisseling geteeld met lelie. Lelie is de laatste jaren getroffen door het PlAMV (Plantago asiatica mosaic virus). Dit virus kan tijdens de teelt via de bodem verspreiden. Ook bij hergebruik van grond afkomstig van PlAMV-lelieteelt is er (tijdens de broei in de kas) een risico op infectie van de nieuwe lelieteelt. Omdat Nerinebollen vaak naast lelies worden geteeld en/of in vruchtwisseling met lelies plaatsvindt, is er een grote angst dat PlAMV mogelijk ook voor grote problemen kan zorgen bij dit gewas. Een besmetting van Nerine met PlAMV zou een decimering van de teelt betekenen. Er is een besmettingsproef uitgevoerd in de periode van augustus 2013 t/m januari 2014 met Nerine bowdeni ‘Favourite’ en ‘Van Roon’ om vast te stellen of Nerine vatbaar is voor een besmetting met PlAMV. Het virus is via verschillende methoden overgebracht op Nerine, maar vervolgens is bij geen enkele plant of bol besmetting aangetoond, terwijl dit wel het geval was bij controle leliebollen/planten. Op basis van dit onderzoek kan de conclusie worden getrokken dat Nerine niet vatbaar is voor PlAMV.
    Damherten in de Amsterdamse Waterleidingduinen. Hun invloed op het duinlandschap en de kwaliteit van enkele habitats
    Haperen, A.M.M. van; Kooijman, A.M. ; Kuiters, A.T. ; Nijssen, M. ; Roon, J.A. van; Schotsman, N. ; Slings, Q.L. - \ 2013
    Waternet - 35 p.
    Membrane applications for antibiotics production
    Schroën, C.G.P.H. ; Roon, J.L. van; Beeftink, H.H. ; Tramper, J. ; Boom, R.M. - \ 2009
    Desalination 236 (2009)1-3. - ISSN 0011-9164 - p. 78 - 84.
    penicillin acylase - aqueous-solution - cephalosporins - hydrolysis - cephalexin - kinetics - acid
    In the enzymatic production of antibiotics, membranes can be used for different purposes. Since the enzyme is a cost-determining factor, membrane bioreactors in which the ultrafiltration membrane's sole purpose is retention of the `free' enzyme and recycling it to the reaction vessel, were investigated as an alternative for the current immobilised-enzyme based process. The membrane bioreactor was tested for two reactions, the production of one of the substrates for the antibiotic synthesis, and the actual enzymatic synthesis reaction. The first process could be improved considerably if the pH regulation took place right after the membrane, therewith creating a small loop that prevented direct contact of the enzyme with high pH, for which it is very sensitive. For the latter process, a big advantage was that diffusion limitation, which reduces the yield of the process with immobilised enzyme, does not take place. Besides, options for continuous operation became available. Away from application during the enzymatic reactions, (nanofiltration) membranes were useful for downstream processing of one of the substrates for antibiotic synthesis. Some of the tested membranes showed separation behaviour, which was strongly pH dependent, therewith opening new options for isolation of the desired component
    Membrane applications for antibiotics production
    Schroën, C.G.P.H. ; Roon, J.L. van; Beeftink, H.H. ; Tramper, J. - \ 2007
    Biocatalysts: Measurement, modelling and design of heterogeneity
    Roon, J.L. van; Schroën, C.G.P.H. ; Tramper, J. ; Beeftink, H.H. - \ 2007
    Biotechnology Advances 25 (2007)2. - ISSN 0734-9750 - p. 137 - 147.
    monodisperse double emulsions - scanning-electron-microscopy - membrane emulsification - enzyme distribution - penicillin acylase - immobilization - cephalexin - distributions - tomography - stability
    Multiple phenomena are involved in conversions by immobilized biocatalysts. A paradox is identified between analytical desires on one hand and analytical boundary conditions on the other: while the study of interdependent phenomena would call for their simultaneous analysis in an integrated context, the available experimental options may impose a series of separate and dedicated analyses. From this analysis, bottlenecks in particle performance may be identified, if possible supported by a mechanistic model and performance criteria. Subsequently, a strategy for further biocatalyst development may be chosen. Finally, possibilities for future improvement of biocatalysts are discussed for various fields of research. Some examples of recent developments in enzyme and matrix characteristics, reactor operation, and micro-technology are discussed
    Rational design of an immobilized biocatalyst
    Tramper, J. ; Roon, J.L. van; Schroën, C.G.P.H. ; Beeftink, H.H. - \ 2007
    NPT Procestechnologie 14 (2007)1. - ISSN 1380-3638 - p. 11 - 13.
    A multicomponent reaction-diffusion model of a heterogeneously distributed immobilized enzyme
    Roon, J.L. van; Arntz, M.M.H.D. ; Kallenberg, A.I. ; Paasman, M.A. ; Tramper, J. ; Schroën, C.G.P.H. ; Beeftink, H.H. - \ 2006
    Applied Microbiology and Biotechnology 72 (2006)2. - ISSN 0175-7598 - p. 263 - 278.
    kinetically controlled synthesis - cephalexin - acylase
    A physical model was derived for the synthesis of the antibiotic cephalexin with an industrial immobilized penicillin G acylase, called Assemblase. In reactions catalyzed by Assemblase, less product and more by-product are formed in comparison with a free-enzyme catalyzed reaction. The model incorporates reaction with a heterogeneous enzyme distribution, electrostatically coupled transport, and pH-dependent dissociation behavior of reactants and is used to obtain insight in the complex interplay between these individual processes leading to the suboptimal conversion. The model was successfully validated with synthesis experiments for conditions ranging from heavily diffusion limited to hardly diffusion limited, including substrate concentrations from 50 to 600 mM, temperatures between 273 and 303 K, and pH values between 6 and 9. During the conversion of the substrates into cephalexin, severe pH gradients inside the biocatalytic particle, which were previously measured by others, were predicted. Physical insight in such intraparticle process dynamics may give important clues for future biocatalyst design. The modular construction of the model may also facilitate its use for other bioconversions with other biocatalysts
    Enzyme distribution and matrix characteristics in biocatalytic particles
    Roon, J.L. van; Boom, R.M. ; Paasman, M.A. ; Tramper, J. ; Schroën, C.G.P.H. ; Beeftink, H.H. - \ 2005
    Journal of Biotechnology 119 (2005). - ISSN 0168-1656 - p. 400 - 415.
    membrane-forming system - equilibrium thermodynamics - 2 polymers - chitosan - hydrogels - gelatin - acylase
    In a study of Assemblase®, an industrial immobilized penicillin-G acylase, various electron microscopic techniques were used to relate intra-particle enzyme heterogeneity with the morphological heterogeneity of the support material at various levels of detail. Transmission electron microscopy was used for the study of intra-particle penicillin-G acylase distribution in Assemblase® particles of various sizes; it revealed an abrupt increase in enzyme loading at the particle surface (1.4-fold) and in the areas (designated halo's) surrounding internal macro-voids (7.7-fold). Cryogenic field-emission scanning electron microscopy related these abrupt local enzyme heterogeneities to local heterogeneity of the support material by revealing the presence of dense top layers surrounding both the particle exterior and the internal macro-voids. Furthermore, it showed a very distinct morphological appearance of the halo. Most probably, all these regions contained relatively more chitosan than gelatin (the polymers Assemblase® was constructed of), which suggested local polymer demixing during particle production. A basic thermodynamic line of reasoning suggested that a difference in hydrophilicity between the two polymers induced local demixing. In the future, thermodynamic knowledge on such polymer interactions resulting in matrix heterogeneity may be used as a tool for biocatalyst design
    Heterogeneity and scale in the rational design of an immobilized biocatalyst
    Roon, J.L. van - \ 2005
    Wageningen University. Promotor(en): Hans Tramper, co-promotor(en): Rik Beeftink; Karin Schroen. - [S.l.] : s.n. - ISBN 9789085042464 - 209
    katalysatoren - immobilisatie - enzymen - enzymactiviteit - synthese - antibiotica - catalysts - immobilization - enzymes - enzyme activity - synthesis - antibiotics - cum laude
    cum laude graduation (with distinction)
    Field-emission scanning electron microscopy analysis of morphology and enzyme distribution within an industrial biocatalytic particle
    Roon, J.L. van; Aelst, A.C. van; Schroën, C.G.P.H. ; Tramper, J. ; Beeftink, H.H. - \ 2005
    Scanning 27 (2005)4. - ISSN 0161-0457 - p. 181 - 189.
    cephalexin
    Field-emission scanning electron microscopy (FESEM) was used in a technical feasibility study to obtain insight into the internal morphology and the intraparticle enzyme distribution of Assemblase®, an industrial biocatalytic particle containing immobilized penicillin-G acylase. The results were compared with previous studies based on light and transmission electron microscopic techniques. The integrated FESEM approach yielded the same quantitative results as the microscopic techniques used previously. Given this technical equivalence, the integrated approach offers several advantages. First, the single preparation method and detection system avoids interpretation discrepancies between corresponding areas that were examined for different properties with different detection techniques in different samples. Second, the specimen size suitable for whole particle study is virtually unlimited, which simplifies sectioning and puts less stringent demands on the embedding technique. Furthermore, the sensitivity toward enzyme presence and distribution increases because the epitopes inside thick sections become available for labeling. Quick and unambiguous analysis of the relation between particle morphology and enzyme distribution is important because this information may be used in the future for the design of enzyme distributions in which the particle morphology can be used as a control parameter
    Novel approach to quantify immobilized-enzyme distributions
    Roon, J.L. van; Groenendijk, E. ; Kieft, H. ; Schroën, C.G.P.H. ; Tramper, J. ; Beeftink, H.H. - \ 2005
    Biotechnology and Bioengineering 89 (2005)6. - ISSN 0006-3592 - p. 660 - 669.
    scanning laser microscopy - confocal microscopy - diffusion limitation - protein diffusion - methacrylate - acylase
    The quantitative intraparticle enzyme distribution of Assemblase, an industrially employed polydisperse immobilized penicillin-G acylase, was measured. Because of strong autofluorescence of the carrier, the generally applied technique of confocal scanning microscopy could not be used; light microscopy was our method of choice. To do so, Assemblase particles of various sizes were sectioned, labeled with antibodies specifically against the enzyme, and analyzed light microscopically. Image analysis software was developed and used to determine the intraparticle enzyme distribution, which was found to be heterogeneous, with most enzyme located in the outer regions of the particles. Larger particles showed steeper gradients than smaller ones. A mathematical representation of the intraparticle profiles, based on in-stationary enzyme diffusion into the particles, was validated successfully for a broad range of particle sizes using data for volume-averaged particle size and enzyme loading. The enzyme gradients determined in this work will be used as input for a physical model that quantitatively describes the complex behavior of Assemblase. Such a physical model will lead to identification of the current bottlenecks in Assemblase and can serve as a starting point for the design of improved biocatalysts that also may be based on intelligent use of enzyme gradients. (C) 2005 Wiley Periodicals, Inc.
    Groene routes voor de antibiotica-productie
    Schroën, C.G.P.H. ; Roon, J.L. van - \ 2003
    NPT Procestechnologie 4 (2003). - ISSN 1380-3638 - p. 16 - 20.
    Enzyme distribution derived from macroscopic particle behavior of an industrial immobilized penicillin-G acylase
    Roon, J.L. van; Tramper, J. ; Joerink, M. ; Schroën, C.G.P.H. ; Beeftink, H.H. - \ 2003
    Biotechnology Progress 19 (2003)5. - ISSN 8756-7938 - p. 1510 - 1518.
    porous solid supports - active-site titration - diffusion limitation - rate-constant - tool - biocatalyst - performance - cephalexin - parameters - substrate
    The macroscopic kinetic behavior of an industrially employed immobilized penicillin-G acylase, called Assemblase, formed the basis for a discussion on some simple intraparticle biocatalytic model distributions. Assemblase catalyzes the synthesis of the widely used semisynthetic antibiotic cephalexin. Despite the obvious advantages of immobilization, less cephalexin and more of the unwanted byproduct d-(-)-phenylglycine are obtained due to diffusional limitations when the immobilized enzyme is employed. To rationally optimize Assemblase, the parameters particle size, enzyme loading, and enzyme distribution, which severely determine the macroscopic particle performance, were studied on the basis of macroscopic observations. Laser diffraction measurements showed that the particle sizes in Assemblase vary as much as 100-fold. The relative and total enzyme loadings in Assemblase and fractions thereof of different sizes were determined by initial-rate d-(-)-phenylglycine amide hydrolysis, cephalexin synthesis experiments, and active-site titration. These experiments revealed that the loading of penicillin-G acylase in Assemblase was inversely correlated with the particle diameter. Apart from enzyme loadings, estimates on the intraparticle enzyme distribution came from cephalexin synthesis experiments, where mass-transport limitations were present. Although this method cannot provide the level of detail of specific labeling experiments, it is simple, fast, and cheap. Within the set of simple model predictions, a heterogeneous enzyme distribution with most biocatalyst present in the outer region of the particle (within the outer 100 m) gave the best description of the observed behavior, although no exact correlation was established. Highly detailed determination of intraparticle enzyme distributions must come from immunolabeling
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