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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    Chemical structure predicts the effect of plant‐derived low molecular weight compounds on soil microbiome structure and pathogen suppression
    Gu, Yian ; Wang, Xiaofang ; Yang, Tianjie ; Friman, Ville Petri ; Geisen, Stefan ; Wei, Zhong ; Xu, Yangchun ; Jousset, Alexandre ; Shen, Qirong - \ 2020
    Functional Ecology (2020). - ISSN 0269-8463


    1. Plant‐derived low molecular weight compounds play a crucial role in shaping soil microbiome functionality. While various compounds have been demonstrated to affect soil microbes, mout data are case‐specific and do not provide generalizable predictions on their effects. Here we show that the chemical structural affiliation of low molecular weight compounds typically secreted by plant roots – sugars, amino acids, organic acids and phenolic acids – can predictably affect microbiome diversity, composition and functioning in terms of plant disease suppression.

    2. We amended soil with single or mixtures of representative compounds, mimicking carbon deposition by plants. We then assessed how different classes of compounds, or their combinations, affected microbiome composition and the protection of tomato plants from the soil‐borne Ralstonia solanacearum bacterial pathogen.

    3. We found that chemical class predicted well the changes in microbiome composition and diversity. Organic and amino acids generally decreased the microbiome diversity compared to sugars and phenolic acids. These changes were also linked to disease incidence, with amino acids and nitrogen‐containing compound mixtures inducing more severe disease symptoms connected with a reduction in bacterial community diversity.

    4. Together, our results demonstrate that low molecular weight compounds can predictably steer rhizosphere microbiome functioning providing guidelines to engineer microbiomes based on root exudation patterns by specific plant cultivars or crop regimes.
    The effect of microbial inoculant origin on the rhizosphere bacterial community composition and plant growth-promotion
    Gu, Yian ; Dong, Ke ; Geisen, Stefan ; Yang, Wei ; Yan, Yaner ; Gu, Dalu ; Liu, Naisen ; Borisjuk, Nikolai ; Luo, Yuming ; Friman, Ville Petri - \ 2020
    Plant and Soil 452 (2020). - ISSN 0032-079X - p. 105 - 117.
    Diversity - Microbial inoculation - Microbial transplants - Plant growth-promotion - Rhizosphere microbiota - Soil functioning

    Aims: Microbial inoculation has been proposed as a potential approach for rhizosphere engineering. However, it is still unclear to what extent successful plant growth-promoting effects are driven by the origin of the microbial inocula and which taxa are responsible for the plant-beneficial effects. Methods: We conducted a microbial transplant experiment by using different microbial inocula (and nutrient controls) isolated from forest, soybean and tomato field soils and determined their effects on tomato plant biomass and nutrient assimilation in sterilized tomato soil. Rhizosphere bacterial communities were compared at the end of the experiment and correlative and machine learning analyses used to identify potential keystone taxa associated with the plant growth-promotion. Results: Microbial inoculants had a clear positive effect on plant growth compared to control nutrient inoculants. Specifically, positive effects on the plant biomass were significantly associated with microbial inoculants from the forest and soybean field soils, while microbial inoculants from the forest and tomato field soils had clear positive effects on the plant nutrient assimilation. Soil nutrients alone had relatively minor effects on rhizosphere bacterial communities. However, the origin of microbial inoculants had clear effects on the structure of bacterial community structure with tomato and soybean inoculants having positive effects on the diversity and abundance of bacterial communities, respectively. Specifically, Streptomyces, Luteimonas and Enterobacter were identified as the potential keystone genera affecting plant growth. Conclusions: The origin of soil microbiome inoculant can predictably influence plant growth and nutrient assimilation and that these effects are associated with certain key bacterial genera.

    Pesticide lifecycle management in agriculture and public health : Where are the gaps?
    Berg, Henk van den; Gu, Baogen ; Grenier, Beatrice ; Kohlschmid, Eva ; Al-Eryani, Samira ; Silva Bezerra, Haroldo Sergio da; Nagpal, Bhupender N. ; Chanda, Emmanuel ; Gasimov, Elkhan ; Velayudhan, Raman ; Yadav, Rajpal S. - \ 2020
    Science of the Total Environment 742 (2020). - ISSN 0048-9697
    Insecticide resistance - Lifecycle management - Pest control - Pesticide management - Risk reduction - Vector control

    Pesticide lifecycle management encompasses a range of elements from legislation, regulation, manufacturing, application, risk reduction, monitoring, and enforcement to disposal of pesticide waste. A survey was conducted in 2017–2018 to describe the contemporary global status of pesticide lifecycle management, to identify where the gaps are found. A three-tiered questionnaire was distributed to government entities in 194 countries. The response rate was 29%, 27% and 48% to the first, second and third part of the questionnaire, respectively. The results showed gaps for most of the selected indicators of pesticide management, suggesting that pesticide efficacy and safety to human health and the environment are likely being compromised at various stages of the pesticide lifecycle, and at varying degrees across the globe. Low-income countries generally had the highest incidence of gaps. Particular shortcomings were deficiencies in pesticide legislation, inadequate capacity for pesticide registration, protection against occupational exposure to pesticides, consumer protection against residues in food, and environmental protection against pesticide contamination. Policy support for, and implementation of, pesticide use-reduction strategies such as integrated pest management and integrated vector management has been inadequate across regions. Priority actions for structural improvement in pesticide lifecycle management are proposed, including pesticide use-reduction strategies, targeted interventions, and resource mobilization.

    Field performance of different maize varieties in growth cores at natural and reduced mycorrhizal colonization : yield gains and possible fertilizer savings in relation to phosphorus application
    Wang, Xin Xin ; Werf, Wopke van der; Yu, Yang ; Hoffland, Ellis ; Feng, Gu ; Kuyper, Thomas W. - \ 2020
    Plant and Soil 450 (2020)1-2. - ISSN 0032-079X - p. 613 - 624.
    Crop - Genetic variation - In-growth cores - Landrace - Maize - Mycorrhizal colonization - Phosphorus

    Aims: The benefits of arbuscular mycorrhizal fungi (AMF) on yield and phosphorus (P) uptake of crops have commonly been studied by inoculating a single mycorrhizal fungal species in pot experiments. Yet, how the native AMF community affects the performance of different maize varieties under field conditions remains obscure. Methods: In-growth cores with and without rotation were used in three soils that differed in P application to assess shoot biomass, P uptake, and mycorrhizal colonization of three maize varietal groups, encompassing four inbred lines, 12 hybrids, and four landraces. Results: Rotating cores drastically reduced mycorrhizal colonization, biomass and P uptake for each varietal group at every P level. Performance of plants at natural mycorrhizal colonization at 30 kg P ha−1 was equal to that of reduced-mycorrhizal plants at 60 kg P ha−1, suggesting the potential for adequate mycorrhizal management to save P fertilizer. Conclusion: There were no significant differences between varietal groups for mycorrhizal responsiveness, confirming that the ability to associate with and benefit from AMF has been maintained in modern breeding. Mycorrhizal plants both exhibited higher P acquisition efficiency and higher P use efficiency than reduced-mycorrhizal plants. Disadvantages of in-growth cores should be duly considered.

    Dietary Isomalto/Malto-Polysaccharides Increase Fecal Bulk and Microbial Fermentation in Mice
    Mistry, Rima H. ; Borewicz, Klaudyna ; Gu, Fangjie ; Verkade, Henkjan J. ; Schols, Henk A. ; Smidt, Hauke ; Tietge, Uwe J.F. - \ 2020
    Molecular Nutrition & Food Research 64 (2020)12. - ISSN 1613-4125
    bile acids - cholesterol - IMMP - microbiota - polysaccharides - prebiotics - short-chain fatty acids

    Scope: The prevalence of metabolic-syndrome-related disease has strongly increased. Nutritional intervention strategies appear attractive, particularly with novel prebiotics. Isomalto/malto-polysaccharides (IMMPs) represent promising novel prebiotics that promote proliferation of beneficial bacteria in vitro. The present study investigates for the first time the in vivo effects of IMMP in mice. Methods and results: C57BL/6 wild-type mice received control or IMMP-containing (10%, w/w) diets for 3 weeks. IMMP leads to significantly more fecal bulk (+26%, p < 0.05), higher plasma non-esterified fatty acids (colorimetric assay, +10%, p < 0.05), and lower fecal dihydrocholesterol excretion (mass spectrometry, −50%, p < 0.05). Plasma and hepatic lipid levels (colorimetric assays following lipid extraction) are not influenced by dietary IMMP, as are other parameters of sterol metabolism, including bile acids (gas chromatography/mass spectrometry). IMMP is mainly fermented in the cecum and large intestine (high-performance anion exchange chromatography). Next-generation sequencing demonstrates higher relative abundance of Bacteroides and butyrate producers (Lachnospiraceae, Roseburia Odoribacter) in the IMMP group. Conclusion: The combined results demonstrate that IMMP administration to mice increases fecal bulk and induces potentially beneficial changes in the intestinal microbiota. Further studies are required in disease models to substantiate potential health benefits.

    The association between breastmilk oligosaccharides and faecal microbiota in healthy breastfed infants at two, six, and twelve weeks of age
    Borewicz, Klaudyna ; Gu, Fangjie ; Saccenti, Edoardo ; Hechler, Christine ; Beijers, Roseriet ; Weerth, Carolina de; Leeuwen, Sander S. van; Schols, Henk A. ; Smidt, Hauke - \ 2020
    Scientific Reports 10 (2020)1. - ISSN 2045-2322

    Several factors affect gut microbiota development in early life, among which breastfeeding plays a key role. We followed 24 mother-infant pairs to investigate the associations between concentrations of selected human milk oligosaccharides (HMOs) in breastmilk, infant faeces, and the faecal microbiota composition in healthy, breastfed infants at two, six and 12 weeks of age. Lactation duration had a significant effect on breastmilk HMO content, which decreased with time, except for 3-fucosyllactose (3FL) and Lacto-N-fucopentaose III (LNFP III). We confirmed that microbiota composition was strongly influenced by infant age and was associated with mode of delivery and breastmilk LNFP III concentration at two weeks, with infant sex, delivery mode, and concentrations of 3′sialyllactose (3′SL) in milk at six weeks, and infant sex and Lacto-N-hexaose (LNH) in milk at 12 weeks of age. Correlations between levels of individual breastmilk HMOs and relative abundance of OTUs found in infant faeces, including the most predominant Bifidobacterium OTUs, were weak and varied with age. The faecal concentration of HMOs decreased with age and were strongly and negatively correlated with relative abundance of OTUs within genera Bifidobacterium, Parabacteroides, Escherichia-Shigella, Bacteroides, Actinomyces, Veillonella, Lachnospiraceae Incertae Sedis, and Erysipelotrichaceae Incertae Sedis, indicating the likely importance of these taxa for HMO metabolism in vivo.

    Rhizosphere protists are key determinants of plant health
    Xiong, Wu ; Song, Yuqi ; Yang, Keming ; Gu, Yian ; Wei, Zhong ; Kowalchuk, George A. ; Xu, Yangchun ; Jousset, Alexandre ; Shen, Qirong ; Geisen, Stefan - \ 2020
    Microbiome 8 (2020)1. - ISSN 2049-2618
    Pathogen of Ralstonia solanacearum - Plant health - Predator-prey interactions - Protists - Rhizosphere - Secondary metabolite genes

    Background: Plant health is intimately influenced by the rhizosphere microbiome, a complex assembly of organisms that changes markedly across plant growth. However, most rhizosphere microbiome research has focused on fractions of this microbiome, particularly bacteria and fungi. It remains unknown how other microbial components, especially key microbiome predators - protists - are linked to plant health. Here, we investigated the holistic rhizosphere microbiome including bacteria, microbial eukaryotes (fungi and protists), as well as functional microbial metabolism genes. We investigated these communities and functional genes throughout the growth of tomato plants that either developed disease symptoms or remained healthy under field conditions. Results: We found that pathogen dynamics across plant growth is best predicted by protists. More specifically, communities of microbial-feeding phagotrophic protists differed between later healthy and diseased plants at plant establishment. The relative abundance of these phagotrophs negatively correlated with pathogen abundance across plant growth, suggesting that predator-prey interactions influence pathogen performance. Furthermore, phagotrophic protists likely shifted bacterial functioning by enhancing pathogen-suppressing secondary metabolite genes involved in mitigating pathogen success. Conclusions: We illustrate the importance of protists as top-down controllers of microbiome functioning linked to plant health. We propose that a holistic microbiome perspective, including bacteria and protists, provides the optimal next step in predicting plant performance. [MediaObject not available: see fulltext.]

    Mycorrhizal impacts on root trait plasticity of six maize varieties along a phosphorus supply gradient
    Wang, Xin-Xin ; Li, Hongbo ; Chu, Qun ; Feng, Gu ; Kuyper, Thomas W. ; Rengel, Zed - \ 2020
    Plant and Soil 448 (2020). - ISSN 0032-079X - p. 71 - 86.
    Morphological traits - Physiological traits - Root/shoot ratio - Specific root length

    Background and aims: Plasticity of plants refers to their ability to produce different phenotypes in different environments. Plants show plasticity aboveground as well as belowground. The influence of the arbuscular mycorrhizal fungal (AMF) symbiosis on root plasticity is poorly known. This study aimed to quantify plasticity of root-system related, morphological, physiological or mycorrhizal traits along a soil phosphorus (P) supply gradient. Methods: Six varieties of maize (Zea mays L.) were grown in pots with or without AMF at five rates of P supply. Fifteen root traits were measured and calculated after seven weeks of growth. Results: Root system traits (biomass and length) and physiological traits (phosphatase activity at the root surface and in the rhizosphere) showed high plasticity along the P gradient, whereas morphological traits (specific root length and root diameter) exhibited low plasticity. Mycorrhizal presence reduced root-system plasticity (biomass and length), increased morphological-trait plasticity (specific root length and proportion of fine roots), but had little effects on other traits. Conclusion: Our results indicate that trait plasticity related to the root system constitutes the most important adaptive strategy for maize to variation in P supply, and that the mycorrhizal symbiosis reduces root-system plasticity.

    Designing intercrops for high yield, yield stability and efficient use of resources: Are there principles?
    Stomph, Tjeerd Jan ; Dordas, Christos ; Baranger, Alain ; Rijk, Joshua de; Dong, Bei ; Evers, Jochem ; Gu, Chunfeng ; Li, Long ; Simon, Johan ; Jensen, Erik Steen ; Wang, Qi ; Wang, Yuyun ; Wang, Zishen ; Xu, Huasen ; Zhang, Chaochun ; Zhang, Lizhen ; Zhang, Wei Ping ; Bedoussac, Laurent ; Werf, Wopke van der - \ 2019
    In: Advances in Agronomy Academic Press Inc. (Advances in Agronomy ) - p. 1 - 50.
    Biotic stresses - Cropping system design - Light - Nutrients - Product quality - Resource use efficiency - Water

    Intercropping is the simultaneous cultivation of plant species in the same field for a considerable proportion of their growing periods. Interest in intercropping for sustainable agriculture is on the rise and the number of scientific studies on intercropping is strongly increasing. Here we assess the current status of knowledge on factors that determine yield, yield stability and resource use efficiency of intercropping as compared to sole cropping. Distinguishing resource use into acquisition and conversion shows that intercrops are mainly improving acquisition rather than conversion efficiency. We also make an attempt to quantify the importance of reduced biotic stresses through pests, diseases, and weeds. We particularly focus on blank spots in the knowledge and possible bias in existing literature and ask which research approaches are needed to advance the field and pave the way for a wider usage of intercropping in modern sustainable agriculture.

    Improved phosphoric acid recovery from sewage sludge ash using layer-by-layer modified membranes
    Paltrinieri, Laura ; Remmen, Kirsten ; Müller, Barbara ; Chu, Liangyong ; Köser, Joachim ; Wintgens, Thomas ; Wessling, Matthias ; Smet, Louis C.P.M. de; Sudhölter, Ernst J.R. - \ 2019
    Journal of Membrane Science 587 (2019). - ISSN 0376-7388
    Layer-by-layer - Phosphate recovery - Polyelectrolyte - Sewage sludge ash - Water treatment

    We report an advanced treatment method for phosphoric acid recovery from leached sewage sludge ash. Layer-by-layer (LbL) polyelectrolyte deposition has been used as a tool to modify and convert a hollow ultrafiltration membrane into a nanofiltration (NF) LbL membrane for H3PO4 recovery. To build the LbL membrane, poly(styrenesulfonate) PSS was chosen as polyanion, while three different polycations were used: a permanently charged polyelectrolyte, poly(diallyldimethylammonium chloride), PDADMAC; a pH-dependent charged polyelectrolyte poly(allylamine hydrochloride), PAH; and a PAH modified with guanidinium groups (PAH-Gu). Based on detailed surface characterizations (AFM, XPS and Zeta-potential) it was concluded that both charge density and pH-responsiveness of the polycations are key parameters to control the final membrane surface structure and transport properties. The surface properties of LbL-coated membranes were correlated with the membrane filtration performance, when exposed to the real leached sewage sludge ash solution. The highest permeability was recorded for (PDADMAC/PSS)6, a result that was rationalized on its loose, and possibly less interpenetrated, structure, followed by (PAH-Gu/PSS)6 characterized by a more dense, compact layer. H3PO4 recovery was the highest in the case of (PDADMAC/PSS)6, but the retention of multivalent metals (Fe3+ and Mg2+) was low, leading to a more contaminated permeate. The opposite trend was observed for (PAH-Gu/PSS)6, resulting in a less metal-contaminated, but also a less H3PO4-concentrated permeate. Our LbL-modified membranes were found to improve the permeability and H3PO4 recovery compared to a commercially available acid-resistant NF membrane.

    Glucosinolate variability between turnip organs during development
    Bonnema, Guusje ; Lee, Jun Gu ; Shuhang, Wang ; Lagarrigue, David ; Bucher, Johan ; Wehrens, Ron ; Vos, Ric De; Beekwilder, Jules - \ 2019
    PLoS ONE 14 (2019)6. - ISSN 1932-6203

    Turnip (Brassica rapa spp. rapa) is an important vegetable species, with a unique physiology. Several plant parts, including both the turnip tubers and leaves, are important for human consumption. During the development of turnip plants, the leaves function as metabolic source tissues, while the tuber first functions as a sink, while later the tuber turns into a source for development of flowers and seeds. In the present study, chemical changes were determined for two genotypes with different genetic background, and included seedling, young leaves, mature leaves, tuber surface, tuber core, stalk, flower and seed tissues, at seven different time points during plant development. As a basis for understanding changes in glucosinolates during plant development, the profile of glucosinolates was analysed using liquid chromatography (LC) coupled to mass spectrometry (MS). This analysis was complemented by a gene expression analysis, focussed on GLS biosynthesis, which could explain part of the observed variation, pointing to important roles of specific gene orthologues for defining the chemical differences. Substantial differences in glucosinolate profiles were observed between above-ground tissues and turnip tuber, reflecting the differences in physiological role. In addition, differences between the two genotypes and between tissues that were harvested early or late during the plant lifecycle. The importance of the observed differences in glucosinolate profile for the ecophysiology of the turnip and for breeding turnips with optimal chemical profiles is discussed.

    Correlating Infant Fecal Microbiota Composition and Human Milk Oligosaccharide Consumption by Microbiota of 1-Month-Old Breastfed Infants
    Borewicz, Klaudyna ; Gu, Fangjie ; Saccenti, Edoardo ; Arts, I.C.W. ; Penders, John ; Thijs, Carel ; Leeuwen, Sander S. van; Lindner, Cordula ; Nauta, Arjen ; Leusen, Ellen van; Schols, Henk A. ; Smidt, Hauke - \ 2019
    Molecular Nutrition & Food Research (2019). - ISSN 1613-4125
    breastfeeding - human milk oligosaccharide - microbial clusters - microbiome

    Scope: Understanding the biological functions of human milk oligosaccharides (HMOs) in shaping gastrointestinal (GI) tract microbiota during infancy is of great interest. A link between HMOs in maternal milk and infant fecal microbiota composition is examined and the role of microbiota in degrading HMOs within the GI tract of healthy, breastfed, 1-month-old infants is investigated. Methods and results: Maternal breast milk and infant feces are from the KOALA Birth Cohort. HMOs are quantified in milk and infant fecal samples using liquid chromatography-mass spectrometry. Fecal microbiota composition is characterized using Illumina HiSeq 16S rRNA gene amplicon sequencing. The composition is associated with gender, delivery mode, and milk HMOs: Lacto-N-fucopentaose I and 2′-fucosyllactose. Overall, Bifidobacterium, Bacteroides, Escherichia–Shigella, and Parabacteroides are predominating genera. Three different patterns in infant fecal microbiota structure are detected. GI degradation of HMOs is strongly associated with fecal microbiota composition, and there is a link between utilization of specific HMOs and relative abundance of various phylotypes (operational taxonomic units). Conclusions: HMOs in maternal milk are among the important factors shaping GI tract microbiota in 1-month-old breastfed infants. An infant's ability to metabolize different HMOs strongly correlates with fecal microbiota composition and specifically with phylotypes within genera Bifidobacterium, Bacteroides, and Lactobacillus.

    Phenotyping flag leaf nitrogen content in rice using a three-band spectral index
    Wang, Jian Jun ; Li, Zhikang ; Jin, Xiuliang ; Liang, Guohua ; Struik, Paul C. ; Gu, Junfei ; Zhou, Yong - \ 2019
    Computers and Electronics in Agriculture 162 (2019). - ISSN 0168-1699 - p. 475 - 481.
    Chromosome segment substitution lines - Oryza sativa - SPAD-502plus chlorophyll meter - Spectral reflectance

    Accurate, rapid and non-destructive measurements of rice flag leaf nitrogen content (LNC) are crucial for geneticists and breeders. To help design a less expensive, non-destructive, real-time LNC sensor, we developed a Three-Band Difference Ratio (TBDR) spectral index, TBDR (R 755 , R 513 , R 508 ). This spectral index could accurately and rapidly estimate rice LNC in a population of chromosome segment substitution lines with small variation in LNC. The model estimating LNC was validated using a leave-one-out cross-validation technique; the achieved root mean square error was 0.13% and the relative error was 4.74%. In comparison with SPAD-502plus chlorophyll meter readings and commonly used spectral indices, including GreenSeeker- and Crop Circle-based indices, TBDR (R 755 , R 513 , R 508 ) produced higher accuracy in LNC estimation.

    Maize varieties can strengthen positive plant-soil feedback through beneficial arbuscular mycorrhizal fungal mutualists
    Wang, Xin Xin ; Hoffland, Ellis ; Mommer, Liesje ; Feng, Gu ; Kuyper, Thomas W. - \ 2019
    Mycorrhiza 29 (2019)3. - ISSN 0940-6360 - p. 251 - 261.
    AMF species - Maize varieties - Plant-soil feedback - Soil conditioning

    Plant-soil feedback (PSF) describes the process whereby plant species modify the soil environment, which subsequently impacts the growth of the same or another plant species. Our aim was to explore PSF by two maize varieties (a landrace and a hybrid variety) and three arbuscular mycorrhizal fungi (AMF) species (Funneliformis mosseae, Claroideoglomus etunicatum, Gigaspora margarita, and the mixture). We carried out a pot experiment with a conditioning and a feedback phase to determine PSF with different species of AMF and with a non-mycorrhizal control. Sterilized soil was conditioned separately by each variety, with or without AMF; in the feedback phase, each soil community was used to grow each in its “home” soil and in the “away” soil. Plant performance was assessed as shoot biomass, phosphorus (P) concentration and P content, and fungal performance was assessed as mycorrhizal colonization and hyphal length density. Both maize varieties were differentially influenced by AMF in the conditioning phase. In the feedback phase, PSF was generally negative for non-mycorrhizal plants or when plants were colonized by G. margarita, whereas PSF was positive in the other three AMF treatments. When plants were grown on home soil, hyphal length density was larger than on away soil. We conclude that different maize varieties can strengthen positive plant-soil feedback for themselves through beneficial mutualists for themselves, but not across the maize varieties.

    Functionalized Anion-Exchange Membranes Facilitate Electrodialysis of Citrate and Phosphate from Model Dairy Wastewater
    Paltrinieri, Laura ; Huerta, Elisa ; Puts, Theo ; Baak, Willem Van; Verver, Albert B. ; Sudhölter, Ernst J.R. ; Smet, Louis C.P.M. De - \ 2018
    Environmental Science and Technology 53 (2018). - ISSN 0013-936X - p. 2396 - 2404.

    In this study, the preparation of a new, functional anion-exchange membrane (AEM), containing guanidinium groups as the anion-exchanging sites (Gu-100), is described as well as the membrane characterization by XPS, water uptake, permselectivities, and electrical resistances. The functional membrane was also employed in pH-dependent electrodialysis experiments using model dairy wastewater streams. The properties of the new membrane are compared to those of a commercially available anion-exchange membrane bearing conventional quaternary ammonium groups (Gu-0). Guanidinium was chosen for its specific binding properties toward oxyanions: e.g., phosphate. This functional moiety was covalently coupled to an acrylate monomer via a facile two-step synthesis to yield bulk-modified membranes upon polymerization. Significant differences were observed in the electrodialysis experiments for Gu-0 and Gu-100 at pH 7, showing an enhanced phosphate and citrate transport for Gu-100 in comparison to Gu-0. At pH 10 the difference is much more pronounced: for Gu-0 membranes almost no phosphate and citrate transport could be detected, while the Gu-100 membranes transported both ions significantly. We conclude that having guanidinium groups as anion-exchange sites improves the selectivity of AEMs. As the presented monomer synthesis strategy is modular, we consider the implementation of functional groups into a polymer-based membrane via the synthesis of tailor-made monomers as an important step toward selective ion transport, which is relevant for various fields, including water treatment processes and fuel cells.

    Hybrid polyelectrolyte-anion exchange membrane and its interaction with phosphate
    Paltrinieri, Laura ; Poltorak, Lukasz ; Chu, Liangyong ; Puts, Theo ; Baak, Willem van; Sudhölter, Ernst J.R. ; Smet, Louis C.P.M. de - \ 2018
    Reactive and Functional Polymers 133 (2018). - ISSN 1381-5148 - p. 126 - 135.
    Anion-exchange membrane - Electrodialysis - Interaction - Phosphate - Sulfate

    We have investigated in detail properties of hybrid polyelectrolyte-anion exchange membranes (AEMs) having different amounts of a guanidinium-modified poly(allylamine hydrochloride) (PAH-Gu) derivative (2, 5, and 8 wt%). The presence of guanidinium groups at the membrane surface was confirmed by XPS. For 2 and 5 wt% the blended membranes are homogeneous, while at 8 wt% segregation is observed by AFM. The membrane permselectivity and ionic electrical resistance for phosphate reduce upon incorporation of the PAH-Gu in the membrane, reflecting an increased co-ion (H+ and Na+) permeation. We conclude that PAH-Gu loaded in the AEM favors an interaction with phosphate. In electrodialysis, using sodium sulfate and sodium dihydrogen phosphate at equal concentrations in the source phase a slight preference for phosphate was observed. Our work shows that this facile membrane fabrication procedure shows great potential in terms of tuning the membrane properties. One way to boost selective ion transport could be by increasing the number of functional groups in the membrane.

    Effect of the prebiotic fiber inulin on cholesterol metabolism in wildtype mice
    Mistry, Rima H. ; Gu, Fangjie ; Schols, Henk A. ; Verkade, Henkjan J. ; Tietge, Uwe J.F. - \ 2018
    Scientific Reports 8 (2018)1. - ISSN 2045-2322

    Dietary non-digestible carbohydrates are perceived to improve health via gut microbiota-dependent generation of products such as short-chain fatty acids (SCFA). In addition, SCFA are also precursors for lipid and cholesterol synthesis potentially resulting in unwanted effects on lipid metabolism. Inulin is a widely used model prebiotic dietary fiber. Inconsistent reports on the effects of inulin on cholesterol homeostasis have emerged in humans and preclinical models. To clarify this issue, the present study aimed to provide an in-depth characterization of the effects of short-chain (sc)- and long-chain (lc)- inulin on cholesterol synthesis, absorption and elimination in mice. Feeding wildtype C57BL/6J mice diets supplemented with 10% (w/w) of either sc- or lc-inulin for two weeks resulted in approximately 2.5-fold higher fecal SCFA levels (P < 0.01) compared with controls, but had no significant effects on plasma and liver lipids. Subtle shifts in fecal and plasma bile acid species were detected with beta-muricholic acid increasing significantly in plasma of the inulin fed groups (1.7-fold, P < 0.05). However, neither sc-inulin nor lc-inulin affected intestinal cholesterol absorption, mass fecal cholesterol excretion or trans-intestinal cholesterol excretion (TICE). Combined, our data demonstrate that sc- and lc-inulin have no adverse effects on cholesterol metabolism in mice despite increased generation of SCFA.

    Red de bij (KennisOnline in beeld 2018)
    Dooremalen, Coby van - \ 2018
    Roles of nitrogen and cytokinin signals in root and shoot communications in maximizing of plant productivity and their agronomic applications
    Gu, Junfei ; Li, Zhikang ; Mao, Yiqi ; Struik, Paul C. ; Zhang, Hao ; Liu, Lijun ; Wang, Zhiqin ; Yang, Jianchang - \ 2018
    Plant Science 274 (2018). - ISSN 0168-9452 - p. 320 - 331.
    Cytokinin transport - Long-distance signaling - Nitrogen status - Root - shoot relationship - Source-sink relationship

    Nitrogen is an essential, often limiting, factor in plant growth and development. To regulate growth under limited nitrogen supply, plants sense the internal and external nitrogen status, and coordinate various metabolic processes and developmental programs accordingly. This coordination requires the transmission of various signaling molecules that move across the entire plant. Cytokinins, phytohormones derived from adenine and synthesized in various parts of the plant, are considered major local and long-distance messengers. Cytokinin metabolism and signaling are closely associated with nitrogen availability. They are systemically transported via the vasculature from plant roots to shoots, and vice versa, thereby coordinating shoot and root development. Tight linkage exists between the nitrogen signaling network and cytokinins during diverse developmental and physiological processes. However, the cytokinin-nitrogen interactions and the communication systems involved in sensing rhizospheric nitrogen status and in regulating canopy development remain obscure. We review current knowledge on cytokinin biosynthesis, transport and signaling, nitrogen acquisition, metabolism and signaling, and their interactive roles in regulating root-shoot morphological and physiological characteristics. We also discuss the role of spatio-temporal regulation of cytokinins in enhancing beneficial crop traits of yield and nitrogen use efficiency.

    In Vitro Fermentation Behavior of Isomalto/Malto-Polysaccharides Using Human Fecal Inoculum Indicates Prebiotic Potential
    Gu, Fangjie ; Borewicz, Klaudyna ; Richter, Bernadette ; Zaal, Pieter H. van der; Smidt, Hauke ; Buwalda, Pieter L. ; Schols, Henk A. - \ 2018
    Molecular Nutrition & Food Research 62 (2018)12. - ISSN 1613-4125
    Digesta - Enzyme activities - Microbiota - Short chain fatty acids

    Scope: This study characterize intestinal fermentation of isomalto/malto-polysaccharides (IMMPs), by monitoring degradation of IMMPs, production of short chain fatty acids (SCFAs), lactic acid, and succinic acid as well as enzyme activity and microbiota composition. Methods and results: IMMP-94 (94% α-(1→6) glycosidic linkages), IMMP-96, IMMP-27, and IMMP-dig27 (IMMP-27 after removal of digestible starch segments) are fermented batchwise in vitro using human fecal inoculum. Fermentation digesta samples are taken for analysis in time up till 48 h. The fermentation of α-(1→6) glycosidic linkages in IMMP-94, IMMP-96, and IMMP-dig27 starts after 12 h and finishes within 48 h. IMMP-27 fermentation starts directly after inoculation utilizing α-(1→4) linked glucosyl residues; however, the utilization of α-(1→6) linked glucoses is delayed and start only after the depletion of α-(1→4) linked glucose moieties. SCFAs are produced in high amounts with acetic acid and succinic acid being the major products next to propionic acid and butyric acid. The polysaccharide fraction is degraded into isomalto-oligosaccharides (IMOs) mainly by extracellular enzymes. The smaller IMOs are further degraded by cell-associated enzymes. Overall microbial diversity and the relative abundance of Bifidobacterium and Lactobacillus, significantly increase during the fermentation of IMMPs. Conclusion: IMMP containing segments of α-(1→6) linked glucose units are slowly fermentable fibers with prebiotic potential.

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