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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    Feruloyl Esterases for Biorefineries : Subfamily Classified Specificity for Natural Substrates
    Underlin, Emilie N. ; Frommhagen, Matthias ; Dilokpimol, Adiphol ; Erven, Gijs van; Vries, Ronald P. de; Kabel, Mirjam A. - \ 2020
    Frontiers in Bioengineering and Biotechnology 8 (2020). - ISSN 2296-4185
    biomass - corn stover - feruloyl esterases - hydroxycinnamic acids - lignin-carbohydrate complex - pectin - wheat straw - xylan

    Feruloyl esterases (FAEs) have an important role in the enzymatic conversion of lignocellulosic biomass by decoupling plant cell wall polysaccharides and lignin. Moreover, FAEs release anti-oxidative hydroxycinnamic acids (HCAs) from biomass. As a plethora of FAE candidates were found in fungal genomes, FAE classification related to substrate specificity is an indispensability for selection of most suitable candidates. Hence, linking distinct substrate specificities to a FAE classification, such as the recently classified FAE subfamilies (SF), is a promising approach to improve the application of these enzymes for a variety of industrial applications. In total, 14 FAEs that are classified members of SF1, 5, 6, 7, 9, and 13 were tested in this research. All FAEs were investigated for their activity toward a variety of substrates: synthetic model substrates, plant cell wall-derived substrates, including lignin, and natural substrates. Released HCAs were determined using reverse phase-ultra high performance liquid chromatography coupled to UV detection and mass spectrometry. Based on this study, FAEs of SF5 and SF7 showed the highest release of FA, pCA, and diFAs over the range of substrates, while FAEs of SF6 were comparable but less pronounced for diFAs release. These results suggest that SF5 and SF7 FAEs are promising enzymes for biorefinery applications, like the production of biofuels, where a complete degradation of the plant cell wall is desired. In contrast, SF6 FAEs might be of interest for industrial applications that require a high release of only FA and pCA, which are needed as precursors for the production of biochemicals. In contrast, FAEs of SF1, 9 and 13 showed an overall low release of HCAs from plant cell wall-derived and natural substrates. The obtained results substantiate the previous SF classification as a useful tool to predict the substrate specificity of FAEs, which eases the selection of FAE candidates for industrial applications.

    Sugar Beet Pectin Supplementation Did Not Alter Profiles of Fecal Microbiota and Exhaled Breath in Healthy Young Adults and Healthy Elderly
    An, Ran ; Wilms, Ellen ; Smolinska, Agnieszka ; Hermes, Gerben D.A. ; Masclee, Ad A.M. ; Vos, Paul de; Schols, Henk A. ; Schooten, Frederik J. van; Smidt, Hauke ; Jonkers, Daisy M.A.E. ; Zoetendal, Erwin G. ; Troost, Freddy J. - \ 2019
    Nutrients 11 (2019)9. - ISSN 2072-6643
    aging - dietary fiber - elderly - exhaled air - microbiota - pectin - young adults

    Aging is accompanied with increased frailty and comorbidities, which is potentially associated with microbiome perturbations. Dietary fibers could contribute to healthy aging by beneficially impacting gut microbiota and metabolite profiles. We aimed to compare young adults with elderly and investigate the effect of pectin supplementation on fecal microbiota composition, short chain fatty acids (SCFAs), and exhaled volatile organic compounds (VOCs) while using a randomized, double-blind, placebo-controlled parallel design. Fifty-two young adults and 48 elderly consumed 15 g/day sugar beet pectin or maltodextrin for four weeks. Fecal and exhaled breath samples were collected before and after the intervention period. Fecal samples were used for microbiota profiling by 16S rRNA gene amplicon sequencing, and for analysis of SCFAs by gas chromatography (GC). Breath was used for VOC analysis by GC-tof-MS. Young adults and elderly showed similar fecal SCFA and exhaled VOC profiles. Additionally, fecal microbiota profiles were similar, with five genera significantly different in relative abundance. Pectin supplementation did not significantly alter fecal microbiota, SCFA or exhaled VOC profiles in elderly or young adults. In conclusion, aside from some minor differences in microbial composition, healthy elderly and young adults showed comparable fecal microbiota composition and activity, which were not altered by pectin supplementation.

    Water-holding capacity of soluble and insoluble polysaccharides in pressed potato fibre
    Ramasamy, U. ; Gruppen, H. ; Kabel, M.A. - \ 2015
    Industrial Crops and Products 64 (2015). - ISSN 0926-6690 - p. 242 - 250.
    dietary fiber - side-chains - pectin - pulp - fractionation - cellulose - mobility
    Pressed potato fibres (PPF), a by-product of starch production, has a high water-holding capacity (WHC).In this study, it is shown that the WHC is caused by a network of mainly insoluble, non-cellulosic cellwall polysaccharides (CWPs). Despite the solubilization of one-fourth of the CWPs from PPF, repre-senting 40–60 w/w% of pectic CWPs (rhamnosyl, uronyl, galactosyl and arabinosyl residues) presentin PPF, the insoluble residues still had similar WHCs as PPF. Only after enzymatic hydrolysis of mainlynon-cellulosic CWPs, the WHC decreased substantially (by 61%). Combining the cellulose-rich residueobtained after enzyme hydrolysis with a polymeric homogalacturonan (HG)-rhamnogalacturonan-I (RG-I)-arabinogalactan (AG) extract increased the WHC. This increased hydration is suggested to result fromthe observed adsorption of the soluble HG-RG-I-AG to the insoluble cellulose-rich residue. No adsorptionwas observed of the HG-RG-I-AG to an insoluble residue enriched in non-cellulosic CWPs.
    The endo-arabinanase BcAra1 is a novel host-specific virulence factor of the necrotic fungal phytopathogen Botrytis cinerea
    Nafisi, M. ; Stranne, M. ; Zhang, L. ; Kan, J.A.L. van; Sakuragi, Y. - \ 2014
    Molecular Plant-Microbe Interactions 27 (2014)8. - ISSN 0894-0282 - p. 781 - 792.
    wall-degrading enzymes - plant-cell walls - carbohydrate gel-electrophoresis - gene-expression - penicillium-chrysogenum - polysaccharide analysis - aspergillus-aculeatus - side-chains - in-vitro - pectin
    The plant cell wall is one of the first physical interfaces encountered by plant pathogens and consists of polysaccharides, of which arabinan is an important constituent. During infection, the necrotrophic plant pathogen Botrytis cinerea secretes a cocktail of plant cell-wall-degrading enzymes, including endo-arabinanase activity, which carries out the breakdown of arabinan. The roles of arabinan and endo-arabinanases during microbial infection were thus far elusive. In this study, the gene Bcara1 encoding for a novel a-1,5-L-endo-arabinanase was identified and the heterologously expressed BcAra1 protein was shown to hydrolyze linear arabinan with high efficiency whereas little or no activity was observed against the other oligo- and polysaccharides tested. The Bcara1 knockout mutants displayed reduced arabinanase activity in vitro and severe retardation in secondary lesion formation during infection of Arabidopsis leaves. These results indicate that BcAra1 is a novel endo-arabinanase and plays an important role during the infection of Arabidopsis. Interestingly, the level of Bcara1 transcript was considerably lower during the infection of Nicotiana benthamiana compared with Arabidopsis and, consequently, the ¿Bcara1 mutants showed the wild-type level of virulence on N. benthamiana leaves. These results support the conclusion that the expression of Bcara1 is host dependent and is a key determinant of the disease outcome.
    Sensory and health properties of steamed and boiled carrots (Daucus carota ssp. sativus)
    Bongoni, R. ; Stieger, M.A. ; Dekker, M. ; Steenbekkers, B. ; Verkerk, R. - \ 2014
    International Journal of Food Sciences and Nutrition 65 (2014)7. - ISSN 0963-7486 - p. 809 - 815.
    beta-carotene - processed vegetables - cooking methods - fruits - texture - quality - bioavailability - pectin - juice - raw
    This study examined the influences of domestic processing conditions applied by consumers on firmness, colour and amount of phytochemicals and liking and sensory attributes intensity rating of carrots. The aim was to identify a cooking method and time that yields carrots with higher amount of b-carotene while maintaining consumer liking. Instrumentally measured firmness and colour showed comparable degradation trends between cooking methods. While boiling showed a significant decrease in the amount b-carotene after 20 min (19%), steaming maintained the amount (+40%). Cooking method did not show a significant effect on liking and intensity ratings for the majority of the sensory attributes. Medium firm carrots were liked the most and low firm carrots the least. This study demonstrates that for optimum liking, carrots should be in the range of medium firmness. This can be obtained through either cooking methods but steamed carrots possess a higher amount of b-carotene and maintains liking.
    Predictive modelling of vegetable firmness after thermal pre-treatments and steaming
    Dekker, M. ; Dekkers, E. ; Jasper, A. ; Baár, C. ; Verkerk, R. - \ 2014
    Innovative Food Science and Emerging Technologies 25 (2014). - ISSN 1466-8564 - p. 14 - 18.
    pectin - kinetics - texture - fruits
    Texture is an important product property that strongly affects the quality evaluation of processed vegetables by consumers. The rate of texture decrease is dependent on the processing temperature and the type of vegetable. A large data set on instrumental texture measurements of carrot and broccoli was produced with different time–temperature combinations for steaming the vegetables. This data set was fitted with a fractional conversion model to describe the kinetics of texture change. Pre-treating the vegetables by steaming at 50–80 °C can increase the resistance towards softening in a subsequent steaming process. The effect of time and temperature of the thermal pre-treatment on the rate constant of softening during subsequent steaming has been evaluated. A response surface two factor interaction model could well describe this effect. Pre-treatments enable more flexibility to optimise several product properties like health, texture and colour. The predictive model presented here is a valuable tool for this multi-criteria optimisation. Industrial relevance A model to describe the softening of vegetable texture during steaming is presented, and the effect of pre-treatment conditions on the reduction of the subsequent softening rate is included in the model. With this model vegetable texture can be improved by predicting the optimal time and temperature of the pre-treatment. This model can be integrated into a multi-criteria optimization approach to improve other quality attributes and still give a desired texture.
    Waste Not, Want Not: Mild and Selective Catalytic Oxidation of Uronic Acids
    Klis, F. van der; Frissen, A.E. ; Haveren, J. van; Es, D.S. van - \ 2013
    ChemSusChem 6 (2013)9. - ISSN 1864-5631 - p. 1640 - 1645.
    acetalized galactaric acid - sugar-beet pulp - renewable resources - gold catalysts - polyesters - decarboxylation - glucose - chemicals - pectin - fdca
    And isn't it uronic: A mild, highly efficient and selective catalytic oxidation of pectin-derived uronic acids to the corresponding aldaric acids is reported. Fast, quantitative conversions (>99%) of the starting materials are achieved with high selectivity (>97%) at room temperature, using supported gold catalysts and air as oxidizing agent
    Crystal structure of endo-xylogalacturonan hydrolase from Aspergillus tubingensis
    Rozeboom, H.J. ; Beldman, G. ; Schols, H.A. ; Dijkstra, B.W. - \ 2013
    FEBS Journal 280 (2013)23. - ISSN 1742-464X - p. 6061 - 6069.
    site-directed mutagenesis - endopolygalacturonase ii - sequence alignments - features - polysaccharides - processivity - degradation - pectin - niger - polygalacturonase
    Endo-xylogalacturonan hydrolase is a member of glycoside hydrolase family 28 (GH28) that hydrolyzes the glycosidic bond between two ß-xylose-substituted galacturonic acid residues in pectin. Presented here is the X-ray crystal structure of the endo-xylogalacturonan hydrolase from Aspergillus tubingensis (XghA) at 1.75 Å resolution. The high degree of structural conservation in the active site and catalytic apparatus compared with polygalacturonases indicates that cleavage of the substrate proceeds in essentially the same way as found for the other GH28 enzymes. Molecular modeling of a xylosylated tri-galacturonate in the active site identified the amino acid residues involved in substrate binding. They border a substrate-binding cleft that is much wider than in other polygalacturonases, and can accommodate xylosylated substrates. The most extensive interactions appear to occur at subsite +2, in agreement with the enzyme kinetics results, which showed enhanced activity on substrates with a xylose attached to the galacturonic acid bound at subsite +2
    Characterisation of 3-aminoquinoline-derivatised isomeric oligogalacturonic acid by travelling-wave ion mobility mass spectrometry
    Huang, J.H. ; Bakx, E.J. ; Gruppen, H. ; Schols, H.A. - \ 2013
    Rapid Communications in Mass Spectrometry 27 (2013)20. - ISSN 0951-4198 - p. 2279 - 2285.
    cell walls - oligosaccharides - matrix - chromatography - separation - pectin - quantification - resolution
    RATIONALE Mass spectrometry has become a useful technique for elucidating the chemical structures of oligosaccharides. The combined use of chromatography and mass spectrometry for the separation and identification of oligosaccharides has shown much progress in recent years. However, no powerful method has yet been developed to quickly identify isomeric oligosaccharides in complex mixtures. METHODS A rapid travelling-wave ion mobility mass spectrometry (TWIMS-MS) method was developed for the identification of various isomeric oligogalacturonic acids in mixtures and determined their structures, using 3-aminoquinoline (3-AQ) as a labelling agent. RESULTS TWIMS successfully distinguished isomeric oligogalacturonic acids of various degrees of polymerisation (DPs) and levels of methyl-esterification. After derivatisation by 3-AQ, isomeric oligosaccharides of galacturonic acid, with the DP ranging from 2 to 9 and the number of methyl esters ranging from 1 to 5, were identified by 3-AQ-TWIMS-MS. The isomeric oligosaccharides with varying sites of methyl ester substitution were identified by the post-fragmentation mode of TWIMS using 3-AQ labelling to obtain simplified mass spectra. CONCLUSIONS Using the 3-AQ-TWIMS-MS method, the precise distribution of methyl esters within the pectin molecule and isomeric oligogalacturonic acids after enzyme degradation was determined. Simplified product ion mass spectra and precise analysis of the isomers were achieved by labelling 3-AQ at the reducing end of the oligosaccharides. Series of methyl-esterified galacturonic acid oligomers have predictable drift times, depending on the precise position of the methyl ester.
    Enzymatic saccharification of sugar beet pulp for the production of galacturonic acid and arabinose; a study on the impact of the formation of recalcitrant oligosaccharides
    Leijdekkers, A.G.M. ; Bink, J.P.M. ; Geutjes, S. ; Schols, H.A. ; Gruppen, H. - \ 2013
    Bioresource Technology 128 (2013). - ISSN 0960-8524 - p. 518 - 525.
    rhamnogalacturonan regions - ethanol-production - pectin - fermentation - hydrolysis - polysaccharides - pretreatment - cellulose - enzymes
    Enzymatic saccharification of sugar beet pulp was optimized on kg-scale to release the maximum amounts of monomeric galacturonic acid and arabinose with limited concomitant degradation of cellulose, using conditions that are feasible for industrial upscaling. A selected mixture of pectinases released 79% of the galacturonic acid and 82% of the arabinose as monomers from sugar beet pulp while simultaneously degrading only 17% of the cellulose. The recalcitrant structures that were obtained after hydrolysis were characterized using mass spectrometry. The most abundant structures had an average degree of polymerization of 4–5. They were identified as partially acetylated rhamnogalacturonan-oligosaccharides, mostly containing a terminal galacturonosyl residue on both reducing and non-reducing end, partially methyl esterified/acetylated homogalacturonan-oligosaccharides, mostly containing methyl and acetyl esters at contiguous galacturonosyl residues and arabinan-oligosaccharides, hypothesized to be mainly branched. It could be concluded that especially rhamnogalacturonan-galacturonohydrolase, arabinofuranosidase and pectin acetylesterase are lacking for further degradation of recalcitrant oligosaccharides
    Emulsion properties of algae soluble protein isolate from Tetraselmis sp.
    Schwenzfeier, A. ; Helbig, A. ; Wierenga, P.A. ; Gruppen, H. - \ 2013
    Food Hydrocolloids 30 (2013)1. - ISSN 0268-005X - p. 258 - 263.
    in-water emulsions - diffusing wave spectroscopy - whey-protein - physicochemical properties - stabilized emulsions - flocculation - emulsifiers - adsorption - microalgae - pectin
    To study possible applications of microalgae proteins in foods, a colourless, protein-rich fraction was isolated from Tetraselmis sp. In the present study the emulsion properties of this algae soluble protein isolate (ASPI) were investigated. Droplet size and droplet aggregation of ASPI stabilized oil-in-water emulsions were studied as function of isolate concentration (1.25–10.00 mg/mL), pH (3–7), and ionic strength (NaCl 10–500 mM; CaCl2 0–50 mM). Whey protein isolate (WPI) and gum arabic (GA) were used as reference emulsifiers. The lowest isolate concentrations needed to reach d32 = 1 µm in 30% oil-in-water emulsions were comparable for ASPI (6 mg/mL) and WPI (4 mg/mL). In contrast to WPI stabilized emulsions ASPI stabilized emulsions were stable around pH 5 at low ionic strength (I = 10 mM). Flocculation only occurred around pH 3, the pH with the smallest net droplet ¿-potential. Due to the charge contribution of the anionic polysaccharide fraction present in ASPI its droplet ¿-potential remained negative over the whole pH range investigated. An increase in ionic strength (=100 mM) led to a broadening of the pH range over which the ASPI stabilized emulsions were unstable. GA emulsions are not prone to droplet aggregation upon changes in pH or ionic strength, but much higher concentrations are needed to produce stable emulsions. Since ASPI allows the formation of stable emulsions in the pH range 5–7 at low protein concentrations, it can offer an efficient natural alternative to existing protein–polysaccharide complexes.
    TEMPO oxidation of gelatinized potato starch results in acid resistant blocks of glucuronic acid moieties
    Haar, R. ter; Timmermans, J.W. ; Slaghek, T.M. ; Dongen, F.E.M. van; Schols, H.A. ; Gruppen, H. - \ 2010
    Carbohydrate Polymers 81 (2010)4. - ISSN 0144-8617 - p. 830 - 838.
    physicochemical properties - selective oxidation - mediated oxidation - polysaccharides - pectin
    Chemical derivatization is often applied to improve polysaccharide functionality. Primary hydroxyl groups in starch can, for example, be oxidized to aldehydes by using a 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated reaction. The major part of the aldehydo groups is subsequently converted to carboxyl groups by NaOCl. The exact structure of TEMPO-oxidized starch was studied to promote a better understanding of the TEMPO oxidation mechanism and the functionality of oxidized starches. By using weak and strong acidic hydrolysis, and methanolysis, at elevated temperatures, oxidized starches with different degrees of oxidation (DO) were broken down into oligomers and monomers. Analysis of the oligomers by chromatographic and mass spectrometric techniques revealed that blocks of glucuronic acid moieties are present in the oxidized starch polymers. The a(1 ¿ 4) glucuronic acid–glucuronic acid bond was found to be very resistant to breakdown by acids. The a(1 ¿ 4) glucuronic acid–glucose bond also showed increased resistance to acids compared to a(1 ¿ 4) glucose–glucose bonds. The size of the blocks of glucuronic acid moieties increased when DO increased. Furthermore, the presence of clusters of aldehydes close to carboxyl groups directly after oxidation was proven. This implies that TEMPO, which is positively charged in its active state, is apparently attracted by the negatively charged carboxyl groups. Because of this, TEMPO tends to be active in areas where carboxyl groups have already been formed, which leads to a block wise distribution of the glucuronic acid moieties.
    MALDI-TOF MS and CE-LIF Fingerprinting of Plant Cell Wall Polysaccharide Digests as a Screening Tool for Arabidopsis Cell Wall Mutants
    Westphal, Y. ; Schols, H.A. ; Voragen, A.G.J. ; Gruppen, H. - \ 2010
    Journal of Agricultural and Food Chemistry 58 (2010)8. - ISSN 0021-8561 - p. 4644 - 4652.
    capillary-electrophoresis - aspergillus-aculeatus - black-currants - pectin - thaliana - identification - purification - oligosaccharides - biosynthesis - hydrolase
    Cell wall materials derived from leaves and hypocotyls of Arabidopsis mutant and wild type plants have been incubated with a mixture of pure and well-defined pectinases, hemicellulases, and cellulases. The resulting oligosaccharides have been subjected to MALDI-TOF MS and CE-LIF analysis. MALDI-TOF MS analysis provided a fast overview of all oligosaccharides released, whereas CE-LIF-measurements enabled separation and characterization of many oligosaccharides under investigation. Both methods have been validated with leaf material of known mutant Arabidopsis plants and were shown to be able to discriminate mutant from wild type plants. Downscaling of the MALDI-TOF MS and CE-LIF approaches toward the hypocotyl level was established, and the performance of MALDI-TOF MS and CE-LIF was shown in the successful recognition of the Arabidopsis mutant gaut13 as an interesting candidate for further analysis.
    Introducing porous graphitized carbon liquid chromatography with evaporative light scattering and mass spectrometry detection into cell wall oligosaccharide analysis
    Westphal, Y. ; Schols, H.A. ; Voragen, A.G.J. ; Gruppen, H. - \ 2010
    Journal of Chromatography. A, Including electrophoresis and other separation methods 1217 (2010)5. - ISSN 0021-9673 - p. 689 - 695.
    treated eucalyptus wood - hairy ramified regions - capillary-electrophoresis - black-currants - polysaccharides - pectin - xylogalacturonan - quantification - nomenclature - ionization
    Separation and characterization of complex mixtures of oligosaccharides is quite difficult and, depending on elution conditions, structural information is often lost. Therefore, the use of a porous-graphitized-carbon (PGC)-HPLC-ELSD-MSn-method as analytical tool for the analysis of oligosaccharides derived from plant cell wall polysaccharides has been investigated. It is demonstrated that PGC-HPLC can be widely used for neutral and acidic oligosaccharides derived from cell wall polysaccharides. Furthermore, it is a non-modifying technique that enables the characterization of cell wall oligosaccharides carrying, e.g. acetyl groups and methylesters. Neutral oligosaccharides are separated based on their size as well as on their type of linkage and resulting 3D-structure. Series of the planar ß-(1,4)-xylo- and ß-(1,4)-gluco-oligosaccharides are retained much more by the PGC material than the series of ß-(1,4)-galacto-, ß-(1,4)-manno- and a-(1,4)-gluco-oligosaccharides. Charged oligomers such as a-(1,4)-galacturonic acid oligosaccharides are strongly retained and are eluted only after addition of trifluoroacetic acid depending on their net charge. Online-MS-coupling using a 1:1 splitter enables quantitative detection of ELSD as well as simple identification of many oligosaccharides, even when separation of oligosaccharides within a complex mixture is not complete. Consequently, PGC-HPLC-separation in combination with MS-detection gives a powerful tool to identify a wide range of neutral and acidic oligosaccharides derived from various cell wall polysaccharides.
    High-throughput screening of monoclonal antibodies against plant cell wall glycans by hierarchical clustering of their carbohydrate microarray binding profiles
    Moller, I. ; Marcus, S.E. ; Haeger, A. ; Verhertbruggen, Y. ; Verhoef, R.P. ; Schols, H.A. ; Ulvskov, P. ; Mikkelsen, J.D. ; Knox, J.P. ; Willats, W.G.T. - \ 2008
    Glycoconjugate Journal 25 (2008)1. - ISSN 0282-0080 - p. 37 - 48.
    oligosaccharide microarrays - arabinogalactan-proteins - glycomics - pectin - polysaccharides - generation - epitope - carrot - homogalacturonan - glycoproteins
    Antibody-producing hybridoma cell lines were created following immunisation with a crude extract of cell wall polymers from the plant Arabidopsis thaliana. In order to rapidly screen the specificities of individual monoclonal antibodies (mAbs), their binding to microarrays containing 50 cell wall glycans immobilized on nitrocellulose was assessed. Hierarchical clustering of microarray binding profiles from newly produced mAbs, together with the profiles for mAbs with previously defined specificities allowed the rapid assignments of mAb binding to antigen classes. mAb specificities were further investigated using subsequent immunochemical and biochemical analyses and two novel mAbs are described in detail. mAb LM13 binds to an arabinanase-sensitive pectic epitope and mAb LM14, binds to an epitope occurring on arabinogalactan-proteins. Both mAbs display novel patterns of recognition of cell walls in plant materials. Keywords Carbohydrate microarrays - Plant cell walls - Monoclonal antibodies - Hierarchical clustering
    Structure of mixed Beta-lactoglobulin/pectin adsorbed layers at air/water interfaces; a spectroscopy study
    Ganzevles, R.A. ; Fokkink, R.G. ; Vliet, T. van; Cohen Stuart, M.A. ; Jongh, H.H.J. de - \ 2008
    Journal of Colloid and Interface Science 317 (2008)1. - ISSN 0021-9797 - p. 137 - 147.
    air-water-interface - o/w emulsions - neutron reflection - protein adsorption - pectin - casein - films - polysaccharides - complexes - membranes
    Based on earlier reported surface rheological behaviour two factors appeared to be important for the functional behaviour of mixed protein/polysaccharide adsorbed layers at air/water interfaces: (1) protein/polysaccharide mixing ratio and (2) formation history of the layers. In this study complexes of ß-lactoglobulin (positively charged at pH 4.5) and low methoxyl pectin (negatively charged) were formed at two mixing ratios, resulting in negatively charged and nearly neutral complexes. Neutron reflection showed that adsorption of negative complexes leads to more diffuse layers at the air/water interface than adsorption of neutral complexes. Besides (simultaneous) adsorption of protein/polysaccharide complexes, a mixed layer can also be formed by adsorption of (protein/)polysaccharide (complexes) to a pre-formed protein layer (sequential adsorption). Despite similar bulk concentrations, adsorbed layer density profiles of simultaneously and sequentially formed layers were persistently different, as illustrated by neutron reflection analysis. Time resolved fluorescence anisotropy showed that the mobility of protein molecules at an air/water interface is hampered by the presence of pectin. This hampered mobility of protein through a complex layer could account for differences observed in density profiles of simultaneously and sequentially formed layers. These insights substantiated the previously proposed organisations of the different adsorbed layers based on surface rheological data.
    Xylogalacturonan exists in cell walls from various tissues of Arabidopsis thaliana
    Zandleven, J.S. ; Sorensen, S. ; Harbolt, J. ; Beldman, G. ; Schols, H.A. ; Scheller, H.V. ; Voragen, A.G.J. - \ 2007
    Phytochemistry 68 (2007)8. - ISSN 0031-9422 - p. 1219 - 1226.
    enzymatic degradation - polysaccharides - hydrolase - purification - pectin - leaves - apple
    Evidence is presented for the presence of xylogalacturonan (XGA) in Arabidopsis thaliana. This evidence was obtained by extraction of pectin from the seeds, root, stem, young leaves and mature leaves of A. thaliana, followed by treatment of these pectin extracts with xylogalacturonan hydrolase (XGH). Upon enzymatic treatment, XGA oligosaccharides were primarily produced from pectin extracts obtained from the young and mature leaves and to a lesser extent from those originating from the stem of A. thaliana. The oligosaccharide GalA3Xyl was predominantly formed from these pectin extracts. No XGA oligosaccharides were detected in digests of pectin extracts from the seeds and roots. A low number of XGA oligosaccharides was obtained from pectins of A. thaliana. This indicates a uniform distribution of xylose in XGA from A. thaliana. The predominant production of GalA3Xyl, as well as the release of linear GalA oligosaccharides pointed to a lower degree of xylose substitution in XGA from A. thaliana than in XGA from apple and potato. The estimated amount of XGA accounted for approximately 2.5%, 7% and 6% (w/w) of the total carbohydrate in the pectin fraction of the stem, young leaves and mature leaves, respectively.
    Polysaccharide charge density regulating protein adsorption to air/water interfaces by protein/polysaccharide complex formation
    Ganzevles, R.A. ; Kosters, H.A. ; Vliet, T. van; Cohen Stuart, M.A. ; Jongh, H.H.J. de - \ 2007
    The Journal of Physical Chemistry Part B: Condensed Matter, Materials, Surfaces, Interfaces & Biophysical 111 (2007). - ISSN 1520-6106 - p. 12969 - 12976.
    surface shear rheology - beta-lactoglobulin - o/w emulsions - water-interface - kinetics - coacervation - pectin - gum - stability - titration
    Because the formation of protein/polysaccharide complexes is dominated by electrostatic interaction, polysaccharide charge density is expected to play a major role in the adsorption behavior of the complexes. In this study, pullulan (a non-charged polysaccharide) carboxylated to four different charge densities (fraction of carboxylated subunits: 0.1, 0.26, 0.51, and 0.56) was used to investigate the effect of charge density on the properties of mixed protein/polysaccharide adsorbed layers at air/water interfaces. With all pullulan samples, soluble complexes with -lactoglobulin could be formed at low ionic strength, pH 4.5. It was shown that the higher was the pullulan charge density, the more the increase of surface pressure in time was retarded as compared to that for pure -lactoglobulin. The retardation was even more pronounced for the development of the dilatational modulus. The lower dilatational modulus can be explained by the ability of the polysaccharides to prevent the formation of a compact protein layer at the air/water interface due to electrostatic repulsion. This ability of the polysaccharides to prevent "layer compactness" increases with the net negative charge of the complexes. If charge density is sufficient (0.26), polysaccharides may enhance the cohesion between complexes within the adsorbed layer. The charge density of polysaccharides is shown to be a dominant regulator of both the adsorption kinetics as well as the resulting surface rheological behavior of the mixed layers formed. These findings have significant value for the application of complex protein-polysaccharide systems.
    Modulating surface rheology by electrostatic protein/polysaccharide interactions
    Ganzevles, R.A. ; Zinoviadou, K. ; Vliet, T. van; Cohen Stuart, M.A. ; Jongh, H.H.J. de - \ 2006
    Langmuir 22 (2006)24. - ISSN 0743-7463 - p. 10089 - 10096.
    air-water-interface - adsorbed protein layers - beta-lactoglobulin - o/w emulsions - complex coacervation - air/water interface - foam stability - shear rheology - adsorption - pectin
    There is a large interest in mixed protein/polysaccharide layers at air-water and oil-water interfaces because of their ability to stabilize foams and emulsions. Mixed protein/polysaccharide adsorbed layers at air-water interfaces can be prepared either by adsorption of soluble protein/ polysaccharide complexes or by sequential adsorption of complexes or polysaccharides to a previously formed protein layer. Even though the final protein and polysaccharide bulk concentrations are the same, the behavior of the adsorbed layers can be very different, depending on the method of preparation. The surface shear modulus of a sequentially formed ß-lactoglobulin/pectin layer can be up to a factor of 6 higher than that of a layer made by simultaneous adsorption. Furthermore, the surface dilatational modulus and surface shear modulus strongly (up to factors of 2 and 7, respectively) depend on the bulk ß-lactoglobulin/pectin mixing ratio. On the basis of the surface rheological behavior, a mechanistic understanding of how the structure of the adsorbed layers depends on the protein/polysaccharide interaction in bulk solution, mixing ratio, ionic strength, and order of adsorption to the interface (simultaneous or sequential) is derived. Insight into the effect of protein/ polysaccharide interactions on the properties of adsorbed layers provides a solid basis to modulate surface rheological behavior
    Calcium-(organo)aluminum-proton competition for adsorption to tomato root cell walls: Experimental data and exchange model calculations
    Riemsdijk, W.H. van; Keltjens, W.G. ; Postma, J.W.M. - \ 2005
    Environmental Science and Technology 39 (2005)14. - ISSN 0013-936X - p. 5247 - 5254.
    aluminum-toxicity - conformational transitions - calcium pectate - organic-acids - ion behavior - al-binding - growth - pectin - elongation - hypothesis
    Aluminum interacts with negatively charged surfaces in plant roots, causing inhibition of growth and nutrient uptake in plants growing on acid soils. Pectins in the root cell wall form the major cation adsorption surface, with Ca2+ as the main adsorbing cation. Adsorption of Al3+ and Ca2+ to isolated cell wall material of tomato (Lycopersicon esculentum L.) roots was examined at pH 3.00-4.25 and in the presence of the aluminum chelators citrate and malate. Al3+ displaced Ca2+ from its pectic binding sites in the cell wall to a large extent but apparently also bound to non-Ca binding groups, displacing protons. Aluminum adsorption depended on the pH of the solution, with little Al adsorbing to the cell wall material at very low pH (
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