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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PHA’s (Polyhydroxyalkanoates): General information on structure and raw materials for their production : A running document for “Kleinschalige Bioraffinage WP9: PHA”, Task 5
Kootstra, A.M.J. ; Elissen, H.J.H. ; Huurman, Sander - \ 2017
Lelystad : Wageningen UR, PPO/Acrres (Wageningen Plant Research report 727) - 29 p.
biopolymers - biorefinery - polyhydroxyalkanoates - residual streams - bioprocess engineering - biobased chemistry - biobased economy - biopolymeren - bioraffinage - polyhydroxyalkanoaten - reststromen - bioproceskunde - chemie op basis van biologische grondstoffen
This report provides background information on structure and diversity of different polyhydroxyalkanoates (PHA) and on feedstocks for their microbial production. The information that is contained in this report was compiled as a running document for the project “TKI-AgriFood Kleinschalige Bioraffinage” Work Package 9: “Fatty acid and PHA production based on residues” (In Dutch: “Vetzuuren PHA-productie op basis van residuen”) (TKI-AF-12040), and should be seen as such: a compilation of information regarded as interesting for the project partners.
PPS Innovatie slag groeisubstraat tuinbouwketen. Deelproject 1 BioFoam als substraat : Resultaten 2015
Baltissen, A.H.M.C. - \ 2016
Randwijk : Wageningen Plant Research , onderdeel van Wageningen University & Research, Business Unit Bloembollen, Boomkwekerij en Fruit (Praktijkonderzoek Plant & Omgeving rapport 2016-02) - 19 p.
biopolymeren - schuimplastic - productontwikkeling - substraten - vervangmiddelen - materialen uit biologische grondstoffen - biobased economy - bos- en haagplantsoen - boomteelt - naaldbomen als sierplanten - levermossen - biopolymers - plastic foam - product development - substrates - substitutes - biobased materials - woody nursery stock - arboriculture - ornamental conifers - liverworts
BioFoam® zijn geschuimde bolletjes (vergelijkbaar met piepschuim) die worden gemaakt op basis van Polymelkzuur (PLA). PLA is een polymeer (plastic) dat gemaakt wordt uit hernieuwbare grondstoffen zoals mais zetmeel of suikerstroop (uit bijvoorbeeld suikerriet). PLA is 100% hernieuwbaar en volledig biologisch afbreekbaar. Dit project “BioFoam als substraat” is een onderdeel van de PPS “Innovatie slag groeisubstraat tuinbouw keten” en heeft de focus op de inzet BioFoam® als onderdeel van substraat in de boomkwekerij. Dit rapport beschrijft de resultaten van de proef te PPO Randwijk in 2015.
From Beet Pulp To Building Blocks and Polymers Developing Value Added Materials From GalX
Leeuwen, M.B. van; Gootjes, L. ; Vogelzang, W. ; Knoop, J.R.I. ; Haveren, J. van; Es, D.S. van - \ 2016
biobased economy - materialen uit biologische grondstoffen - reststromen - agrarische afvalstoffen - biopolymeren - galacturonzuur - bietenpulp - bioplastics - biobased materials - residual streams - agricultural wastes - biopolymers - galacturonic acid - beet pulp
Poster of the Carbohydrate Competence Center. The increasing demand for 2nd generation bio-based performance materials presents an excellent opportunity for the development of agricultural residues like sugar beet pulp (SBP) as feedstock for renewable polymers. Refining SBP yields various industrially interesting components, such as galacturonic acid. This sugar acid can be transformed into a novel family of bio-based building blocks called GalX. Here we report on the use of GalX building blocks in bio-based polymers.
Biobased chemicals from polyhydroxybutyrate
Spekreijse, Jurjen - \ 2016
Wageningen University. Promotor(en): Johan Sanders, co-promotor(en): Elinor Scott; Harry Bitter. - Wageningen : Wageningen University - ISBN 9789462578630 - 148
bioprocess engineering - biopolymers - waste water treatment - polyhydroxyalkanoates - acrylics - propylene - biomass conversion - biobased chemistry - biobased economy - bioproceskunde - biopolymeren - afvalwaterbehandeling - polyhydroxyalkanoaten - acrylaten - propyleen - biomassaconversie - chemie op basis van biologische grondstoffen

Currently, most chemicals and materials are obtained from fossil resources. After use, these chemicals and materials are converted to CO2. As discussed in chapter 1, this causes a build-up of CO2 in the atmosphere, the main driving force of global warming. In order to reach a sustainable system, biomass could be used as a resource for chemicals and materials instead. A biorefinery approach, where all parts of biomass are used to its full potential is essential. Taking this into consideration, wastewater streams of current biobased processes could be an excellent source for chemicals and materials. However, wastewater is often dilute and heterogeneous of nature. To overcome these challenges, wastewater rich in carbon can be processed by microorganisms to obtain a biodegradable polyester, polyhydroxyalkanoate (PHA). However, the mechanical properties of this polymer make it unsuitable as polymeric material. Moreover, processing of PHA is challenging. To circumvent these issues, we propose a conversion of the inferior PHA to methyl acrylate and propylene (Figure 7.1) which can be used in current processing infrastructure. PHA rich cells are obtained from the purification of wastewater. The PHA obtained can be purified and converted to MC (Figure 7.1, chapter 2) or the PHA rich cells can be used directly (Figure 7.1, chapter 3). For the second step, the conversion of methyl crotonate (MC) to methyl acrylate and propylene, the catalyst was immobilised (Figure 7.1, chapter 4). The current state of ethenolysis reaction on biomass was reviewed (Figure 7.1, chapter 5). The conversion of PHA to methyl acrylate and propylene enables the use of carbon from wastewater streams without the disadvantages related to the direct use of PHA.

In chapter 2, the first step of the conversion of PHA to methyl acrylate and propylene was investigated. Since PHA obtained from wastewater exists mostly as polyhydroxybutyrate (PHB), this was chosen as a starting material for our studies. It was shown that PHB could be converted to MC using methanol at 200 °C.. MC has the advantage of being immiscible with water, which aids its separation. In chapter 2, the pathway of the reaction was clarified, which was subsequently used to optimise the conditions of this conversion. The conversion of PHB to MC proceeds via a thermolysis to crotonic acid (CA), which is followed by an esterification to MC. The formation of CA is the rate determining step below 18 bar, where above 18 bar this changes to the esterification to MC. A selectivity of 60% to MC is obtained with a full conversion of PHB with 18 bar being the optimal pressure for the conversion.

Microorganisms produce PHA within their cells, which poses challenges to the downstream processing of PHA as the material has to be isolated from within the cells and dried. The isolation and drying of PHB is costly and is responsible for a large part of the production costs of PHA. In order to reduce the costs of PHA for the production of biobased chemicals, the conversion of PHA to MC was tested using whole cells. In chapter 3, PHA rich cells were directly converted to MC using the optimised conditions found in chapter 2. The influence of fermentation salts, water and the presence of valerate monomers in the PHA were studied. It was found that the valerate monomers have no influence on the conversion. Fermentation salts do influence the conversion depending on the salt. Magnesium hydroxide catalyses the conversion of PHB to MC, where magnesium sulphate catalyses the formation of methyl 3-hydroxybutyrate as side product. The reaction tolerates up to 20% water, which means that the drying step in the downstream processing of PHA can be significantly reduced.

The second step of the conversion of PHA to methyl acrylate and propylene involves an ethenolysis, a cross metathesis of MC with ethylene. This ethenolysis reaction requires a homogeneous catalyst. One of the most active catalysts for this conversion is the ruthenium based Hovey-Grubbs 2nd generation. However, the required high loading of this catalyst makes it an expensive part of the conversion. In order to enable reusing of the catalyst, immobilisation of the Hovey-Grubbs catalyst was investigated in chapter 4. The catalyst was immobilised inside a metal organic framework (MOF). For this purpose MIL-101-NH2(Al) was used for its large cavities connected by small openings. This allows the catalyst to reside inside the cavities, while the small openings prevent it from leaching out. The catalyst was successfully immobilised using a mechanochemical approach. This method can be applied on other catalysts as well, which was shown by the immobilisation of Zhan catalyst. Both immobilised catalysts show metathesis activity for multiple reaction cycles. It was found that the MOF, MIL-101-NH2(Al), partially undergoes a structural change to form MIL-53-NH2(Al). When MIL-53-NH2(Al) was used as starting MOF the catalyst was trapped but inactive. It was concluded that when starting from MIL-101-NH2(Al), the catalyst trapped in the parts of the material that was converted to MIL-53-NH2(Al) are catalytically inactive.

To investigate the current state of the art of the use of ethenolysis on biomass, a literature review was performed in chapter 5. The results of the ethenolysis of methyl oleate (MO) were compared in order to investigate the most important parameters. It was found that the purity of the ethylene feed has the biggest influence on the turn over numbers (TONs) and that a higher purity ethylene has shown a larger impact on the ethenolysis of MO than the development of novel catalysts. When electron poor substrates are used, the highest TONs are obtained with the less stable Hoveyda-Grubbs 2nd generation. However, no studies were performed on the influence of ethylene purity on these reactions and higher TONs may be achieved using a higher purity ethylene.

In chapter 6, the results and conclusions of the thesis are summarised. The implications of these findings are discussed and suggestions for further research within the field are given.

Nanoscale force sensors to study supramolecular systems
Cingil, E.H. - \ 2016
Wageningen University. Promotor(en): Martien Cohen Stuart, co-promotor(en): Joris Sprakel. - Wageningen : Wageningen University - ISBN 9789462576971 - 136 p.
sensors - supramolecular chemistry - molecules - biopolymers - polymers - methodology - rheology - supramoleculaire chemie - moleculen - biopolymeren - polymeren - methodologie - reologie

Supramolecular systems are solutions, suspensions or solids, formed by physical and non-covalent interactions. These weak and dynamic bonds drive molecular self-assembly in nature, leading to formation of complex ordered structures in high precision. Understanding self-assembly and co-assembly is crucial to unravel and mimic many processes occurring in nature. However, the challenge cannot be easily addressed especially in biological systems as it involves many dynamic interactions which may cooperatively, noncooperatively or competitively generate a complex manifold of interaction pathways. In this thesis, we employed two techniques to understand these complex interactions in various supramolecular systems at the nanoscale 1) multiple particle tracking microrheology to study thermoreversible assembly of triple helices in a collagen-inspired recombinant polypeptide in the form of a triblock copolymer gel former; and 2) polyfluorene-based conjugated polyelctrolyte mechosensors to monitor electrostatic co-assembly dynamics of (i) a recombinant diblock copolypeptide which encapsulates the conjugated polyelectrolyte like a protein capsid and (ii) various synthetic diblock copolymers which forms complex coacervate micelles; and finally the orthogonal self-assembly dynamics of (iii) a recombinant viral coat protein which mimics natural rod-like viruses. These novel polymeric mechanosensors work as versatile, non-invasive tools to detect even low degrees of analyte binding or complex formation due to the stress applied on their conjugated backbone. This mechanical stress causes the polymeric backbone to stretch which can be detected by a shift in its fluorescence spectra.

Chemie - Van suiker naar mobiel : Kennisclip Bogo-project e-learning
Baltissen, A.H.M.C. - \ 2016
Groen Kennisnet
biopolymeren - suiker - biobased economy - biochemie - chemische reacties - polymelkzuur - melkzuur - bioplastics - tuinbouw - lesmaterialen - biopolymers - sugar - biochemistry - chemical reactions - polylactic acid - lactic acid - horticulture - teaching materials
Deze kennisclip maakt onderdeel uit van de lesmodule Biobased Economy van het CIV T&U.
Doodzonde om op te stoken. Lignine de grondstof van de toekomst
Zundert, M. ; Gosselink, R.J.A. - \ 2014
Chemie Magazine 2014 (2014)3. - ISSN 1572-2996 - p. 24 - 27.
biopolymeren - lignine - toepassingen - bioraffinage - innovaties - chemie op basis van biologische grondstoffen - biobased economy - aromatische koolwaterstoffen - biopolymers - lignin - applications - biorefinery - innovations - biobased chemistry - aromatic hydrocarbons
Onhandelbaar, wee barstig en recalcitrant. Zo staat het houtpolymeer lignine bekend. Maar de stof vervangt steeds vaker fenol. En onderzoekers zijn hoopvol over de ontwikkeling van bio-BTX en koolstofvezels uit lignine.
Bioplastic op bestelling : grondstoffen kunnen steeds opnieuw worden geoogst
Didde, R. ; Bolck, C.H. - \ 2014
WageningenWorld (2014)4. - ISSN 2210-7908 - p. 10 - 15.
bioplastics - materialen uit biologische grondstoffen - biobased economy - biopolymeren - markten - biodegradatie - prijsvorming - economische ontwikkeling - biobased materials - biopolymers - markets - biodegradation - price formation - economic development
Bioplastics hebben de wind in de rug. Steeds meer bedrijven overwegen hun producten te maken van kunststoffen met een plantaardige oorsprong. Christiaan Bolck van Wageningen UR Food & Biobased Research helpt ze aan de juiste receptuur.
Bioflocculation of wastewater organic matter at short retention times
Faust, L. - \ 2014
Wageningen University. Promotor(en): Huub Rijnaarts, co-promotor(en): Hardy Temmink. - Wageningen : Wageningen University - ISBN 9789462571716 - 153
afvalwaterbehandeling - uitvlokking - bioreactoren - geactiveerd slib - organische verbindingen - biopolymeren - energieterugwinning - waste water treatment - flocculation - bioreactors - activated sludge - organic compounds - biopolymers - energy recovery
Expositie brengt biobased economy tot leven
Baltissen, A.H.M.C. ; Leeuwen, M.A.E. van; Dijk, W. van - \ 2014
lesmaterialen - tentoonstellingen - biobased economy - materialen uit biologische grondstoffen - biopolymeren - voorlichting - onderwijs - teaching materials - exhibitions - biobased materials - biopolymers - extension - education
Poster met informatie over de mobiele expositie 'Bio-Based'.
Understanding of the self- and co-assembly behavior of recombinant protein polymers : from design to implementation
Golinska, M.D. - \ 2014
Wageningen University. Promotor(en): Martien Cohen Stuart, co-promotor(en): Renko de Vries; Frits de Wolf. - Wageningen : Wageningen University - ISBN 9789461738134 - 165
biopolymeren - eiwitten - zelf-assemblage - recombinant eiwitten - elastine - collageen - enzymatische cross-linking - glutaminase - biopolymers - proteins - self assembly - recombinant proteins - elastin - collagen - enzymatic cross-linking

A key part of the growing field of biomedical sciences deals with the development of new, controlled and biocompatible biomaterials. In this thesis we present results on the design, production, purification and characterization of stimuli responsive protein polymers that could ultimately be used in that field. Protein-polymers are composed of two or three blocks that are able to self- and co-assemble. An important theme in the thesis is to highlight the specific advantages of our new protein polymer for future biomedical applications.

We have used recombinant DNA techniques and expression in methylotrophic yeast Pichia pastorisfor protein production. DNAs encoding various polypeptide blocks were designed, produced using general molecular biology techniques and combined into synthetic genes for protein polymers. Synthetic genes were cloned into P. pastorisexpression vector pPIC9 that integrates into the yeast genome. Yields were high, typically reaching gram-per-liter (of medium).

In Chapter 2we study dual-stimuli (pH, temperature) responsive silk-elastin-like protein polymers (SELPs). These polymers were designed to self- and co-assembly, controlled by both pH and temperature. The first protein is a diblock S24E40composed of 24 silk-like (S) repeats and 40 elastin-like (E) repeats. The other protein is a triblock S12C4E40, in which the Sand Eblocks are separated by a random coil block (C4) that serves as an inert ‘spacer’.

A C2SHSHC2protein polymer, which consists of a pH responsive, positively charged silk-like middle block SH, flanked by two random coil collagen-like blocks C2was studied in Chapter 3.

For this protein have studied fibril formation and gelling properties at pH values close to neutral, that are crucial for biomedical applications. We find that at physiological pH, these proteins form self-healing physical gels that fulfill many requirements for use in biomedical applications.


In Chapter 4we test the influence of enzymatic cross-linking on elasticity andmechanical properties ofhydrogels that include collagen-like domains, using microbial transglutaminase (mTGase) as an enzymatic crosslinker that catalyzes the coupling of glutamines to lysines. We show that even though the collagen-like blocks are not particularly good substrates for the mTGase, the few cross-links that are made have a strong effect on the physical properties of the protein-polymer hydrogels. For silk-collagen fiber gels, the elastic moduli can be increased by a factor of five, and for thermosensitive collagen hydrogels, the enzymatic cross-linking induces qualitatively new behavior, namely shape-memory of hydrogels.

Finally, we study the co-assembly of very asymmetric diblock copolymers with oppositely charged sodium poly(acrylic acid) (NaPAA) with a range of molar masses (Chapter 5). This asymmetric diblock consists of a cationic block of 12 lysines connected to a long (400 amino acid) collagen-like block with a net charge that is nearly zero. For shorter Na-PAA chains, spherical complex coacervates micelles are formed, as have been studied before in our lab. But, for long Na-PAA chains a new self-assembled structure is found: a single (Na-PAA) chain pearl-necklace of complex-coacervate micelles.

The general discussion of the thesis in Chapter 6, focuses on recombinant and natural hydrogels as biomaterials. We point out the specific advantages of recombinant proteins and also indicate where these still need to be improved in order to be used in biomedical applications. Finally, we make some suggestions for further research in this area.

BOGO van groene grondstoffen naar biobased materialen. eigenschappen van polymerlkzuur
Schennink, G.G.J. ; Beukelaer, H.J. de; Molenveld, K. - \ 2013
FBR
lesmaterialen - bioplastics - biopolymeren - polymelkzuur - beroepsopleiding (hoger) - materialen uit biologische grondstoffen - biobased economy - handleidingen - teaching materials - biopolymers - polylactic acid - professional education - biobased materials - guide books
Deze opdracht geeft inzicht in de eigenschappen van PLA en daarmee de toepassingsmogelijkheden. Het praktijkdeel van deze opdracht laat zien hoe door keuze van de juiste PLA typen en temperatuurbehandeling de maximale gebruikstemperatuur (HDT=Heat Distortion Temperature) verhoogd kan worden.
BOGO van groen grondstoffen naar biobased materialen. Van melkzuur naar polymeren.
Knoop, J.R.I. - \ 2013
Wageningen : FRB
lesmaterialen - melkzuur - biopolymeren - polymelkzuur - polymerisatie - chemie - biobased economy - beroepsopleiding (hoger) - handleidingen - teaching materials - lactic acid - biopolymers - polylactic acid - polymerization - chemistry - professional education - guide books
Lesmateriaal (theorie en praktijkopdracht) over de polymerisatie van melkzuur tot polymelkzuur (PLA).
BOGO van groen grondstoffen naar biobased materialen. Van stro naar melkzuur.
Bakker, R.R.C. ; Lopez Contreras, A.M. ; Broek, L.A.M. van den - \ 2013
Wageningen : FBR
lesmaterialen - biopolymeren - melkzuur - stro - fermentatie - beroepsopleiding (hoger) - biobased economy - chemie op basis van biologische grondstoffen - handleidingen - teaching materials - biopolymers - lactic acid - straw - fermentation - professional education - biobased chemistry - guide books
Practicumhandleiding voor hbo. In dit practicum wordt melkzuur gemaakt uit stro.
BOGO van groene grondstoffen naar biobased materialen. Van zetmeel naar plastic.
Broek, L.A.M. van den - \ 2013
Wageningen : FBR Wageningen
lesmaterialen - zetmeel - biopolymeren - bioplastics - handleidingen - chemie op basis van biologische grondstoffen - biobased economy - beroepsopleiding (hoger) - teaching materials - starch - biopolymers - guide books - biobased chemistry - professional education
Practicumhandleiding voor hbo. Met behulp van commercieel zetmeel is het mogelijk om gelen te maken. Door het toevoegen van glycerol tijdens het proces kan men de gel flexibeler maken.
Dual responsive physical networks from asymmetric biosynthetic triblock copolymers
Pham, T.H.T. - \ 2013
Wageningen University. Promotor(en): Martien Cohen Stuart; Jasper van der Gucht, co-promotor(en): Frits de Wolf. - Wageningen : Wageningen UR - ISBN 9789461737359 - 163
polymeren - gels - biopolymeren - biosynthese - elastine - collageen - polymers - biopolymers - biosynthesis - elastin - collagen

The aim of the project is to develop biosynthetically produced amino acid polymers which are composed of three distinct blocks A-C-B, each with a separate function. A is a first self-assembling block capable of ‘recognizing’ (upon a trigger) other A blocks; C is an inert, random coil-like connector, and B is a second self-assembling block. A and B have to be chosen such that they do not cross-assemble. With these molecules it should be possible to fabricate hydrogels in which direct ‘loops’ are excluded. We exploited genetic engineering to design proper genes encoding asymmetric triblock protein polymer and fermentation to produce monodisperse protein polymers. There different asymmetric triblock protein polymers were produced and characterized.

The first molecule, silk-elastin hybrid molecule (SCE), was inspired by natural silk and elastin. The silk-like block (S) forms a pH-sensitive beta-roll (beta-sheet like) structure that further stacks into long fibrils. The elastin-like block(E) has thermo-responsive properties; above the lower critical solution temperature (LCST), it forms aggregates. We find that polymers that have both silk and elastin-like domains show temperature dependent fibril formation. At high temperature, the elastin blocks irreversibly induce bundling and aggregation of fibrils. The presence of the elastin-like block also changes the kinetics of fibril formation. Whereas silk-like protein without elastin forms monodisperse fibrils, the presence of elastin results in polydisperse fibrils due to homogenous nucleation.

The self-assembly of silk-elastin hybrid molecule is further analysed in the presence of NaCl. We find that the thermo-responsive behaviors of elastin-like block are strongly dependent on salt concentration. At high salt concentration, the aggregation transition is much more pronounced. At high pH, where the S block does not self-assemble, the polymer forms micellar aggregates upon heating in the presence of NaCl. At low temperature, lowering the pH leads to fibril formation. When both blocks are induced to self-assemble, the final structure reveals a pathway-dependence. Heating the solution of fibrils formed at low temperature results in fibril aggregates which do not dissociate upon cooling. The pH-triggered fibril formation of preheated protein solutions leads to the formation of large objects, which likely cause sedimentation. The structural difference is also demonstrated clearly in the morphology of gels formed at high protein concentration: whereas the gel formed in the first pathway (first lower the pH, then increase the temperature) is transparent, the gel formed in the latter pathway (first increase the temperature, then lower the pH) is milky and has a higher elastic modulus.

The second type of asymmetric triblock copolymer (TR4H or TR4K) has a collagen-like, triple-helix-forming motif at one end, and a poly cationic block at the other. The collagen-like end-block T consists of 9 (PGP) repeats and forms thermo-responsive triple helices upon cooling. Such helices are reversibly disrupted when the temperature is raised above the melting temperature. The other end-block has 6 positively charged amino acids (histidine-H or lysine-K) and forms micelles when a negatively charged polymer is added. The charge-driven complexation of this block depends on its degree of deprotonation, which is determined by the pKa and the pH. The additives used in this study are a flexible polyanion (polystyrene sulfonate, PSS) and a semi-flexible polyanion (xanthan). We find micelle-to-network transition of the triblock TR4H in complexation with PSS. First, the self-assembly of each end-block is studied separately. As expected, the collagen-like block reversibly forms triple helices upon cooling. The cationic H block forms charge-driven complexes upon adding PSS, leading to micelles with an aggregation number that depends on ionic strength. At high concentration, the micellar TR4H/PSS solutions form a viscoelastic gel upon cooling, which melts at high temperature, indicating the formation of helical junctions between the micelles. Liquid-liquid phase separation is observed when the concentration is below the gelation point (around 90 g/L). This leads to a dilute phase on top of a concentrated gel phase. The phase separation is driven by the attraction between charge-driven micelles caused by the triple helices. It disappears when the solution is heated or when the ionic strength is increased.

The charge-driven complexation of TR4K with xanthan, a negatively charged polysaccharide is also studied. At high temperature and at very low xanthan concentration, the TR4K binds to the xanthan backbone via the charged block K, leading to charge-driven bottle brushes, as indicated by a significant increase in light scattering intensity due to the increased mass. This interaction is dependent on the pH, due to protonation of the cationic K block. The xanthan/TR4K complex shows thermo-sensitivity due to the helical interaction of the collagen-like blocks. At a xanthan concentration around the overlap concentration (~7 g/L), the presence of the triblock results in an increase in elastic modulus of xanthan gels. At high temperature, the elastic modulus increases by 3 times after adding the triblock. As triple helices do not form, this must be due to changes in the entanglement of the bottle brushes. Also the non-linear rheology of the xanthan/TR4K gels differs significantly from that of xanthan alone. At low temperatures when the helical junctions are formed, the elastic modulus increases even further approximately two times compared with the corresponding value at high temperature. This is ascribed to the formation of crosslinks induced by the proteins between the xanthan molecules. The triblock protein modifies the properties of the xanthan hydrogels in three ways: (1) a significant increase in storage modulus, (2) thermo-sensitivity and (3) a two-step strain softening, where the first step is probably due to unbinding of the proteins from the xanthan backbones.

The third molecule is an asymmetric triblock copolymer (TR4T-Cys), which has two triple helix forming end-blocks (T), with a cysteine residue (Cys) added to one of these. Under oxidizing conditions, the cysteine residues can form disulfide bonds between two polymers whereas reducing conditions restore the thiol groups. Since cysteine can form only one S-S bridge, intramolecular loops are prevented. The presence of S-S bonds significantly enhances the thermal stability of the triple helical network. This results in the appearance of two melting temperatures, of which the higher one is due to the S-S stabilized triple helices. The elastic modulus of the physical gels in the presence of S-S bonds is almost 2 times higher than that of the physical gels in the absence of S-S bonds. The relaxation time also triples under oxidizing conditions, which indicates that triple helical knots are also kinetically stabilized by S-S bonds.

In summary, the design of S-C-S (S: functional end-block, C: connector) network-forming components might meet the increasing demands of high performance biomaterials that must be able to build a physical gel under narrowly defined conditions. Such class of telechelic polymer might display various interesting dynamic behaviors including shear banding, self-assembly, rheochaos, and phase-separation. Another aspect is the functionality of the end-block which self-assembles upon triggering. However, connectors often return to the same nodes, resulting in loop formation. Loop formation is a structural imperfection that weakens network connectivity and lowers the material’s elasticity. The asymmetric triblock with two different end-blocks is designed in order to: (1) prevent unimolecular loops and improve mechanical properties (2) achieve multi-responsiveness: this allows us to observe different assembling pathways. In this work, with respect to (1), we indeed observed the decrease in loop formation in physical gels formed by TR4T-Cys due to the formation of S-S bridges. With respect to (2), we indeed obtained multi-responsive hydrogels with all three asymmetric triblock proteins. However, we have only scratched the surface as understanding kinetics of self-assembly and pathway dependent processes. Further investigations are needed to get more insights into how to manipulate various parameters in controlling the final structures.

Plastic zonder olie : lesmodule voor nieuwe scheikunde
Langejan, B. ; Klein Douwel, C. ; Horst, J.J. ter; Tijdink, K. ; Marle, N. van; Klaasen, P. ; Coolen, R. ; Assenbergh, P. van; Sijbers, J.P.J. ; Mast, A. - \ 2013
Wageningen : Wageningen UR - 66
lesmaterialen - bioplastics - biopolymeren - voortgezet onderwijs - kunststoffen - polymerisatie - biobased economy - cradle to cradle - natuur- en milieueducatie - teaching materials - biopolymers - secondary education - plastics - polymerization - nature and environmental education
Lesmodule voor nieuwe scheikunde voor leerlingen uit 5 en 6 vwo. Bioplastics worden gemaakt uit natuurlijke grondstoffen. Als ze de synthetische plastics vervangen kan de voorraad aardolie ontzien worden. Omdat veel bioplastics afbreekbaar zijn, kan ook de berg plastic afval krimpen. Maar zijn bioplastics in staat om ons de reguliere plastics te doen vergeten? Hoe maken we bioplastics met dezelfde veelzijdige eigenschappen als plastic? Waar komen de uiteenlopende eigenschappen van plastics eigenlijk vandaan? De lesmodule ‘Plastic zonder Olie’ gaat op deze en meerdere vragen in. Naast de practica waarin de leerlingen bioplastics gaan maken ligt het zwaartepunt van de module bij een multidisciplinaire slotopdracht.
Green building blocks for biobased plastics: biobased processes and market development
Harmsen, P.F.H. ; Hackmann, M.M. - \ 2013
Wageningen : Wageningen UR - Food & Biobased Research (Green raw materials ) - ISBN 9789461736109 - 77
bioplastics - biopolymeren - chemie op basis van biologische grondstoffen - biobased economy - materialen uit biologische grondstoffen - vinylkunststoffen - polyesters - amiden - polyurethanen - rubber - chemicaliën uit biologische grondstoffen - biopolymers - biobased chemistry - biobased materials - vinyl plastics - amides - polyurethanes - biobased chemicals
From a chemical perspective, nearly all building blocks for plastics can be made using renewable raw materials. However, not every process is commercially feasible. Processes often remain inefficient, products have insufficient purity or the raw materials are simply too expensive. This publication provides more insight into the processes that are currently under development and the companies involved, as well as the current development stage (from R&D to commercial production).
Biosubstraat : Duurzaam substraat op basis van BioFoam
Baltissen, A.H.M.C. ; Molenveld, K. ; Bosch, C. ; Blok, C. ; Reuler, H. van; Sluis, B.J. van der; Dijkema, M.H.G.E. ; Gude, H. - \ 2013
Lisse : Praktijkonderzoek Plant & Omgeving B.V. - 53
substraten - schuimplastic - biopolymeren - tuinbouw - polymelkzuur - proeven - materialen uit biologische grondstoffen - biobased economy - substrates - plastic foam - biopolymers - horticulture - polylactic acid - trials - biobased materials
Doelstelling van het project was het ontwikkelen van een hernieuwbare grondstof/substraat, welke voldoet aan de wensen en eisen van de kwekers en waar een kwalitatief goed product op geteeld kan worden met handhaving of verbetering van het rendement. Het belangrijkste eindproduct is een bio substraat op basis van gemodificeerde BioFoam. De volgende activiteiten hebben bijgedragen aan het realiseren van de doelstelling: • Het ontwikkelen en produceren van diverse varianten gemodificeerde BioFoam en het uitvoeren van een aantal fysische en chemische testen in het laboratorium. • Het bepalen van belangrijke eigenschappen van deze gemodificeerde BioFoam als substraat in combinatie en vergelijking tot andere grondstoffen in het laboratorium • Het uitvoeren van diverse teeltproeven met mengsels van BioFoam met andere grondstoffen • Het in beeld brengen van de voordelen met betrekking tot de ketenkosten. Er is maar een teeltjaar (alleen 2012) gebruikt om testen uit te voeren. Ketens moeten daarom nog deels opgezet worden. • Op basis van de (teelt)proeven zijn wel meer partijen bij het project betrokken geraakt en heeft de markt belangstelling getoond. Het belangrijkste eindproduct is een getest substraat op basis van gemodificeerde BioFoam.
Sustainability aspects of biobased products : comparison of different crops and products from the vegetable oil platform
Meesters, K.P.H. ; Corré, W.J. ; Conijn, J.G. ; Patel, M.K. ; Bos, H.L. - \ 2012
Wageningen : Wageningen UR - Food & Biobased Research (Report / Wageningen UR Food & Biobased Research 1441) - ISBN 9789461739827 - 68
oil plants - plant oils - palm oils - soyabean oil - rapeseed oil - sustainability - sustainability indicators - renewable energy - greenhouse gases - land use - biobased economy - biofuels - biopolymers - olieleverende planten - plantaardige oliën - palmoliën - sojaolie - raapzaadolie - duurzaamheid (sustainability) - duurzaamheidsindicatoren - hernieuwbare energie - broeikasgassen - landgebruik - biobrandstoffen - biopolymeren
This study focusses on the production of vegetable oil based products. A limited number of aspacts of the sustainability of the full chain (from agriculture to product at the factory gate) was evaluated. Three different vegetable oils were taken into account: palm oil, soy oil and rapeseed oil. Also three different products made from vegetable oil were evaluated: biodiesel, polyol (a raw material for production of PU foams) and resin. In the present study, sustainability of these products was evaluated through the following parameters: Non-Renewable Energy Usage (NREU) (GJ per ton of product); Greenhouse Gas (GHG) emissions (ton CO2-equivalent per ton of product); Land use (ha/ton vegetable oil) and NREU and GHG emission avoided (GJ or ton CO2-equivalent per hectare of land).
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