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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    Adsorption of rapeseed proteins at oil/water interfaces. Janus-like napins dominate the interface
    Ntone, Eleni ; Wesel, Tessa van; Sagis, Leonard M.C. ; Meinders, Marcel ; Bitter, Johannes H. ; Nikiforidis, Constantinos V. - \ 2021
    Journal of Colloid and Interface Science 583 (2021). - ISSN 0021-9797 - p. 459 - 469.
    Cruciferins - Emulsions - Interfacial rheology - Janus-particles - Napins - Oil bodies - Oleosomes - Plant proteins

    Plants offer a vast variety of protein extracts, typically containing multiple species of proteins that can serve as building blocks of soft materials, like emulsions. However, the role of each protein species concerning the formation of emulsions and interfaces with diverse rheological properties is still unknown. Therefore, deciphering the role of the individual proteins in an extract is highly relevant, since it determines the optimal level of purification, and hence the sustainability aspects of the extract. Here, we will show that when oil/water emulsions were prepared with a rapeseed protein extract containing napins and cruciferins (in a mass ratio of 1:1), only napins adsorbed at the interface exhibiting a soft solid-like rheological behavior. The dominance of napins at the interface was ascribed to their small size (radius r = 1.7 nm) and its unique Janus-like structure, as 45% of the amino acids are hydrophobic and primarily located at one side of the protein. Cruciferins with a bigger size (r = 4.4 nm) and a more homogeneous distribution of the hydrophobic domains couldn't reach the interface, but they appear to just weakly interact with the adsorbed layer of napins.

    Molybdenum and tungsten carbides can shine too
    Führer, M. ; Haasterecht, T. Van; Bitter, J.H. - \ 2020
    Catalysis Science & Technology 10 (2020)18. - ISSN 2044-4753 - p. 6089 - 6097.

    In this perspective, we argue that carbides of transition metals such as molybdenum and tungsten hold great potential for the catalytic conversions of future feedstocks due to their ability to remain active in the presence of impurities in the feedstock. The presence of N and S impurities, found in increasing amounts in fossil-based feedstocks and also in new renewable feedstocks (such as biomass) may cause the carbides to convert to their respective nitrides or sulphides. These phases are catalytically active for similar reactions to the carbides and so these impurities would not lead to complete catalyst deactivation as they do for noble metal catalysts. Establishing the full potential of transition metal carbides as catalysts requires studies that use real feedstocks to look into the role of heteroatoms during the processing of fossil and novel feedstocks. This journal is

    On the Emulsifying Properties of Self-Assembled Pea Protein Particles
    Sridharan, Simha ; Meinders, Marcel B.J. ; Bitter, Johannes H. ; Nikiforidis, Constantinos V. - \ 2020
    Langmuir 36 (2020)41. - ISSN 0743-7463 - p. 12221 - 12229.
    Pea proteins are promising oil-in-water emulsifying agents at both neutral and acidic conditions. In an acidic environment, pea proteins associate to form submicrometer-sized particles. Previous studies suggested that the emulsions at acidic pH were stabilized due to a Pickering mechanism. However, protein particles can be in equilibrium with protein molecules, which could play a significant role in the stabilization of emulsion droplets. Therefore, we revisited the emulsion stabilization mechanism of pea proteins at pH 3 and investigated whether the protein particles or the protein molecules are the major emulsifying agent. The theoretical and experimental surface load of dispersed oil droplets were compared, and we found that protein particles can cover only 3.2% of the total oil droplet surface, which is not enough to stabilize the droplets, whereas protein molecules can cover 47% of the total oil droplet surface. Moreover, through removing protein particles from the mixture and emulsifying with only protein molecules, the contributions of pea protein molecules to the emulsifying properties of pea proteins at pH 3 were evaluated. The results proved that the protein molecules were the primary stabilizers of the oil droplets at pH 3.
    CO2 Conversion by Combining a Copper Electrocatalyst and Wild-type Microorganisms
    Chatzipanagiotou, Konstantina Roxani ; Jourdin, Ludovic ; Buisman, Cees J.N. ; Strik, David P.B.T.B. ; Bitter, Johannes H. - \ 2020
    ChemCatChem 12 (2020)15. - ISSN 1867-3880 - p. 3900 - 3912.
    bio-catalysis - carbon dioxide fixation - catalytic cooperation - formate electrosynthesis - supported catalysts

    Carbon dioxide (CO2) can be converted to valuable products using different catalysts, including metal or biological catalysts (e. g. microorganisms). Some products formed by metal electrocatalysts can be further utilized by microorganisms, and therefore catalytic cooperation can be envisioned. To prevent cumbersome separations, it is beneficial when both catalyst work under the same conditions, or at least in the same reaction medium. Here, we will show that a formate-producing copper electrocatalyst can function in a biological medium. Furthermore, we will show that the effluent of the copper-containing reactor can be used without purification as the sole medium for a bio-reactor, inoculated with a mixed culture of microorganisms. In that second reactor, formate, H2 and CO2 are consumed by the microorganisms, forming acetate and methane. Compared to simple buffer electrolyte, catalytic activity of copper was improved in the presence of microbial growth medium, likely due to EDTA (Ethylenediaminetetraacetic acid) present in the latter.

    Synthesis and characterization of a supported Pd complex on carbon nanofibers for the selective decarbonylation of stearic acid to 1-heptadecene : The importance of subnanometric Pd dispersion
    Ochoa, Elba ; Henao, Wilson ; Fuertes, Sara ; Torres, Daniel ; Haasterecht, Tomas Van; Scott, Elinor ; Bitter, Harry ; Suelves, Isabel ; Pinilla, Jose Luis - \ 2020
    Catalysis Science & Technology 10 (2020)9. - ISSN 2044-4753 - p. 2970 - 2985.

    Production of linear α-olefins from renewable sources is gaining increasing attention because it allows the transition from the current petrochemical synthesis route to a more sustainable scenario. In this work, we describe the synthesis and characterization of an innovative catalyst based on a di-μ-chloro-bis[palladium(ii) anthranilate] complex highly dispersed by incipient wetness impregnation over acyl chlorinated carbon nanofibers. The subnanometric dispersion of the metal complex allowed higher catalytic efficiency for the selective decarbonylation of stearic acid to 1-heptadecene as compared to the reference homogenous catalyst. The best catalytic performance (90 mol% selectivity, 71 mol% conversion, and TON = 484) was achieved under mild reaction conditions (atmospheric pressure, 140 °C) with a Pd loading in solution of 0.14 mol%. The post-mortem catalyst characterization and the recyclability tests evidenced the high stability of the catalyst. The highly dispersed catalyst developed in this work provides new opportunities in the rational design of more efficient catalytic systems for the sustainable transformation of fatty acids.

    Not sequentially but simultaneously : Facile extraction of proteins and oleosomes from oilseeds
    Ntone, Eleni ; Bitter, Johannes H. ; Nikiforidis, Constantinos V. - \ 2020
    Food Hydrocolloids 102 (2020). - ISSN 0268-005X
    Emulsifiers - Oil bodies - Oil-in-water systems - Oleosomes - Plant proteins - Rapeseed proteins

    Oilseeds represent a sustainable source of oils and proteins that can replace those of animal origin. However, the extraction of oil and proteins from oilseeds currently requires multiple steps and is plagued by undesired reactions occurring during the extraction, which limits valorization. In this paper, we describe a successful method for the simple simultaneous extraction of proteins and oil (as intact oleosomes). Non-defatted dehulled rapeseeds served as oilseed model. First, an aqueous extraction step at pH 9.0 was performed resulting in a protein-oleosome extract, with extraction yields of 78.8 ±0.2 wt% and 82.8 ±0.4 wt% of proteins and oleosomes respectively. Further separation resulted in a protein-rich and an oleosome-rich mixture. The oleosomes were recovered as high oil volume oil-in-water emulsion, while simple filtration of the protein-rich mixture led to a highly soluble (81.4 ±1.9 wt%) protein concentrate. Following this extraction method, complexation between proteins and phenolic compounds was prevented, a clear advantage over the existing methods. These findings emphasize the importance of designing new processes for the extraction of oilseed proteins and oleosomes that could initiate their use in food systems.

    Pea flour as stabilizer of oil-in-water emulsions : Protein purification unnecessary
    Sridharan, Simha ; Meinders, Marcel B.J. ; Bitter, Johannes H. ; Nikiforidis, Constantinos V. - \ 2020
    Food Hydrocolloids 101 (2020). - ISSN 0268-005X
    Emulsions - Natural emulsifiers - Pea proteins - Plant proteins - Yellow peas

    Plant proteins have recently gained considerable attention as stabilizers of food-grade oil-in-water emulsions. However, the separation of plant proteins from their native matrix can be cumbersome due to the molecular complexity of plants. This issue could be alleviated by avoiding the protein purification step. In this work, we show that native pea flour containing 50 wt% starch and 20 wt% protein has similar interfacial properties compared to concentrated pea protein systems (~55 wt% protein). Interfacial tension profile of pea flour was similar to that of concentrated pea protein, indicating that proteins are the primary stabilizing agents of the interface. The fabricated oil-in-water emulsions (10.0 wt% oil) made with pea flour or pea protein concentrate containing 0.2 and 0.3 wt% protein showed a similar monomodal droplet size distribution. Moreover, both emulsions stabilized by the pea flour and the pea protein concentrate had similar rheological properties, showing that starch granules did not have any impact on the physical properties. This work clearly showed that stable oil-in-water emulsions can be produced with pea flour and further purification of pea proteins is not necessary.

    Assessment of air gap membrane distillation for milk concentration
    Moejes, S.N. ; Wonderen, G.J. van; Bitter, J.H. ; Boxtel, A.J.B. van - \ 2020
    Journal of Membrane Science 594 (2020). - ISSN 0376-7388
    Membrane distillation - Milk - Network optimization - Process design - Reverse osmosis

    Multi-effect evaporation is the state of the art for concentration of liquid food products to high solid content. Membrane technology with reverse-osmosis and membrane distillation offer an alternative. For the concentration of milk, a reverse osmosis and air-gap membrane distillation network was modelled and optimized. Fouling dynamics and scheduling are taken into account. Reverse osmosis is favourable until its maximum achievable concentration. Air gap membrane distillation is, despite the low operational temperatures, energy intensive for the concentration of milk. A large recirculation flow to keep sufficient cross flow has to be heated and cooled, and the costs for heating and cooling dominate the total costs for product concentration. Moreover, fouling increases the energy requirements. The optimal system for air gap membrane distillation has only one stage operating at a high concentration and relative low flux. Applying multiple stages reduces the investment costs due to smaller units, but the heating and cooling costs increase. Major opportunities to improve the performance of air gap membrane distillation for concentration of milk are: 1) increase the cold and hot side temperatures to their maximum acceptable values, 2) develop spacers that allow lower linear flow velocities in the system and thus lower recirculation rates, and 3) make use of available waste heat.

    Towards an Industrial Process for Au-Catalyzed Carbohydrate Oxidations: Evaluation of Batch- vs. Continuous Reactors
    Klis, Frits van der; Gootjes, Linda ; Haveren, Jacco van; Es, Daan van; Bitter, Harry - \ 2019
    CO2 capture from air and utilization: Thermodynamic boundaries of adsorption processes
    Cabrera Rodriguez, Carlos ; Kiewidt, Lars ; Haasterecht, T. van; Masoud, Nazila ; Bitter, J.H. - \ 2019
    Oxidation of polydisperse starch in porous catalysts: modelling hindered diffusion
    Noord, Aster Van; Hoogstad, Tim ; Kiewidt, Lars ; Bitter, J.H. - \ 2019
    Assessing the influence of reactivity and diffusivity of different molecular weight fractions in the conversion of polydisperse feedstocks
    Hoogstad, Tim ; Noord, Aster Van; Buwalda, P.L. ; Kiewidt, Lars ; Bitter, J.H. - \ 2019
    Assessing the influence of reactivity and diffusivity of different molecular sizes in the conversion of polydisperse feedstocks
    Hoogstad, Tim ; Noord, Aster Van; Buwalda, P.L. ; Kiewidt, Lars ; Bitter, J.H. - \ 2019
    The case of pea flour as emulsifier: Protein Purification unnecessary?
    Sridharan, Lakshminarasimhan ; Meinders, M.B.J. ; Bitter, J.H. ; Nikiforidis, K. - \ 2019
    Heeft Sint iets groens in petto?
    Bitter, Harry - \ 2019
    Carbohydrate conversions: a combination of challenges
    Bitter, J.H. - \ 2019
    (non) Noble metal catalysts in biobased conversions
    Bitter, J.H. - \ 2019
    Carbohydrate based conversions: From catalyst preparation to reactor design
    Bitter, J.H. - \ 2019
    Activated Carbon, Carbon Nanofibers and Carbon-Covered Alumina as Support for W2C in Stearic Acid Hydrodeoxygenation
    Souza Macedo, Luana ; Teixeira Da Silva, Victor ; Bitter, Johannes Hendrik - \ 2019
    ChemEngineering 3 (2019)1. - ISSN 2305-7084
    Carbon materials play a crucial role in sorbents and heterogeneous catalysis and are widely used as catalyst support for several reactions. This paper reports on an investigation of tungsten carbide (W2C) catalyst on three types of carbon support, namely activated carbon (AC), carbon nanofibers (CNF) and carbon-covered alumina (CCA). We evaluated their activity and selectivity in stearic acid hydrodeoxygenation at 350 °C and 30 bar H2. Although all three W2C catalysts displayed similar intrinsic catalytic activities, the support did influence product distribution. At low conversions (<5%), W2C/AC yielded the highest amount of oxygenates relative to W2C/CNF and W2C/CCA. This suggests that the conversion of oxygenates into hydrocarbons is more difficult over W2C/AC than over W2C/CNF and W2C/CCA, which we relate to the lower acidity and smaller pore size of W2C/AC. The support also had an influence on the C18-unsaturated/C18-saturated ratio. At conversions below 30%, W2C/CNF presented the highest C18-unsaturated/C18-saturated ratio in product distribution, which we attribute to the higher mesopore volume of CNF. However, at higher conversions (>50%), W2C/CCA presented the highest C18-unsaturated/C18-saturated ratio in product distribution, which appears to be linked to W2C/CCA having the highest ratio of acid/metallic sites.
    Direct CO₂ capture from air - towards better sorbents
    Masoud, Nazila ; Bordanaba Florit, G. ; Haasterecht, T. van; Bitter, J.H. - \ 2019
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