Staff Publications

Staff Publications

  • external user (warningwarning)
  • Log in as
  • language uk
  • About

    '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.

    We have a manual that explains all the features 

    Current refinement(s):

    Records 1 - 20 / 136

    • help
    • print

      Print search results

    • export

      Export search results

    Check title to add to marked list
    Convergent evolution of hetero-oligomeric cellulose synthesis complexes in mosses and seed plants
    Li, Xingxing ; Speicher, Tori L. ; Dees, Dianka C.T. ; Mansoori, Nasim ; McManus, John B. ; Tien, Ming ; Trindade, Luisa M. ; Wallace, Ian S. ; Roberts, Alison W. - \ 2019
    The Plant Journal (2019). - ISSN 0960-7412
    cell wall - cellulose - cellulose synthase - cellulose synthesis complex - convergent evolution - Physcomitrella patens

    In seed plants, cellulose is synthesized by rosette-shaped cellulose synthesis complexes (CSCs) that are obligate hetero-oligomeric, comprising three non-interchangeable cellulose synthase (CESA) isoforms. The moss Physcomitrella patens has rosette CSCs and seven CESAs, but its common ancestor with seed plants had rosette CSCs and a single CESA gene. Therefore, if P. patens CSCs are hetero-oligomeric, then CSCs of this type evolved convergently in mosses and seed plants. Previous gene knockout and promoter swap experiments showed that PpCESAs from class A (PpCESA3 and PpCESA8) and class B (PpCESA6 and PpCESA7) have non-redundant functions in secondary cell wall cellulose deposition in leaf midribs, whereas the two members of each class are redundant. Based on these observations, we proposed the hypothesis that the secondary class A and class B PpCESAs associate to form hetero-oligomeric CSCs. Here we show that transcription of secondary class A PpCESAs is reduced when secondary class B PpCESAs are knocked out and vice versa, as expected for genes encoding isoforms that occupy distinct positions within the same CSC. The class A and class B isoforms co-accumulate in developing gametophores and co-immunoprecipitate, suggesting that they interact to form a complex in planta. Finally, secondary PpCESAs interact with each other, whereas three of four fail to self-interact when expressed in two different heterologous systems. These results are consistent with the hypothesis that obligate hetero-oligomeric CSCs evolved independently in mosses and seed plants and we propose the constructive neutral evolution hypothesis as a plausible explanation for convergent evolution of hetero-oligomeric CSCs.

    Schimmel zet stro om in veevoer
    Cone, J.W. ; Sonnenberg, A.S.M. ; Nayan, Nazri ; Mao, Lei ; Ratni, E. - \ 2018
    biobased economy - animal nutrition - biomass - agricultural wastes - cellulose - fungi
    De toekomst van hout in de biobased economy
    Annevelink, E. ; Harmsen, P.F.H. ; Spijker, J.H. - \ 2018
    Vakblad Natuur Bos Landschap 15 (2018)141. - ISSN 1572-7610 - p. 7 - 11.
    biobased economy - hout - biobrandstoffen - biomassa - hernieuwbare energie - materialen uit biologische grondstoffen - cellulose - lignine - vezels - biobased economy - wood - biofuels - biomass - renewable energy - biobased materials - cellulose - lignin - fibres
    De laatste jaren is de biobased economy sterk gegroeid door allerlei activiteiten, variërend van fundamenteel onderzoek naar nieuwe biobased toepassingen, tot het op commerciële schaal vervaardigen van biobased producten. Welke kansen biedt dit voor hout en houtige biomassa en wat zijn de verwachte effecten op de houtmarkt?
    Short communication : insoluble fibres in supplemental pre-weaning diets affect behaviour of suckling piglets
    Clouard, C. ; Stokvis, L. ; Bolhuis, J.E. ; Hees, H.M.J. van - \ 2018
    Animal 12 (2018)2. - ISSN 1751-7311 - p. 329 - 333.
    cellulose - dietary fibre - manipulative behaviours - mastication - pigs
    We investigated the effect of offering supplementary dietary fibres to suckling piglets on their behaviour and performance before weaning. From 5 to 22 days of age, suckling piglets were offered a high-fibre diet (HF; 5% cellulose; n=5 litters), or a control low-fibre diet (n=5 litters). Piglets were housed with the sows in individual farrowing pens, and had access to maternal milk until weaning, at 23 days of age. Behaviours of six focal piglets per pen were scored at 6, 16 and 21 days of age. All piglets were individually weighed at 5, 15 and 20 days of age and feed intake was measured daily at the pen level. Piglets on the HF diet were more active than controls (P=0.05), and spent more time suckling or massaging the udder (P=0.01) and interacting with pen mates (P=0.008). Time spent manipulating pen mates, which may reflect re-directed foraging activity in the absence of substrate, accounted for most of the time spent interacting with pen mates (⩾73% of total time spent interacting). Dietary fibres had no effect on BW and feed intake. In conclusion, inclusion of cellulose in the supplemental diet of suckling piglets affects behaviour, with no deleterious effects on performance before weaning.
    Fermentatie is hot: nieuwe toepassingen van een oeroude techniek
    Smid, E.J. ; Hugenholtz, J. - \ 2017
    biofuels - biobased economy - bioenergy - chemical industry - nutrition - fermentation - cellulose - bacteria - biomass
    Anaerobic digestion of cellulose and hemicellulose in the presence of humic acids
    Azman, Samet - \ 2016
    Wageningen University. Promotor(en): Fons Stams; Grietje Zeeman, co-promotor(en): Caroline Plugge. - Wageningen : Wageningen University - ISBN 9789462579613 - 189
    humic acids - hydrolysis - anaerobic digestion - cellulose - hemicelluloses - biomass - renewable energy - energy recovery - biogas - fermentation - bioprocess engineering - humuszuren - hydrolyse - anaërobe afbraak - cellulose - hemicellulosen - biomassa - hernieuwbare energie - energieterugwinning - biogas - fermentatie - bioproceskunde

    Research on the hydrolysis step of the AD became more important with the increased use of recalcitrant waste products such as manure, sewage sludge and agricultural biomass for biogas production. Hydrolysis is often the rate limiting step of the overall AD. Hydrolysis enhancement is one of the required steps to optimise biogas production. Despite the progress to overcome the limitations of hydrolysis, inhibition of hydrolysis is still poorly researched. Humic acid-like molecules (HA) are one of the inhibitors of the anaerobic hydrolysis and their effect on the overall AD process is generally overlooked.

    In this thesis, the HA inhibition on anaerobic digestion of cellulosic material and mitigation strategies, using cation and enzyme addition, to overcome the inhibition were investigated. In addition, the microbial community dynamics during AD in the presence and absence of HA were examined. In this scope, in Chapter 2, we reviewed the literature and pinpointed the urgent need for comprehensive studies on the role of hydrolytic microorganisms and environmental factors that effects their abundance within biogas plants. Consequently, the hydrolysis mechanism and involved hydrolytic enzymes were discussed. The overall discussion showed that a holistic approach, including microbiological and engineering studies should be chosen to disclose the role of hydrolytic microbes within biogas reactors. In Chapter 3 and, Chapter 4 the effect of HA on anaerobic cellulose hydrolysis and methanogenesis, in batch wise incubations is reported, respectively. Our results showed that pulse addition of 5 g L-1 HA caused a 50 % decrease in hydrolysis rate of anaerobic cellulose degradation (Chapter 3). Moreover, VFA accumulation was observed in the presence of HA during the anaerobic cellulose degradation, which indicated the possible inhibition of HA on methanogenesis. Based on the results of Chapter 3, pure cultures of methanogens and a mixed culture were tested to study the vulnerability of methanogenesis to HA inhibition. Hydrogenotrophic methanogenesis in pure cultures was inhibited by more than 75% in the presence of 1 g L-1 HA whereas, acetoclastic methanogenesis by Methanosaeta concilii was only slightly affected by HA up to 3 g L-1. When methanogenic granular sludge was incubated with HA, the specific methanogenic activity tests showed less inhibition, when compared to the pure cultures of methanogens. HA inhibition was also observed during long-term CSTR operation at an HRT of 20 days, 35°C and a mixture of cellulose and xylan as a subtrate (Chapter 6). 8 g L-1 HA inhibited the hydrolysis efficiency of the cellulose and xylan digestion by 40 % and concomitantly reduced the methane yields.

    Mitigation of the HA inhibition is required to increase the hydrolysis efficiency and methane yields of cellulosic biomass digestion. Therefore, two different strategies were tested for their potential use as mitigation agents, viz. addition of cations such as, calcium magnesium and iron (Chapter 3 and Chapter 6) and addition of hydrolytic enzymes (Chapter 6). Addition of magnesium, calcium and iron salts mitigated the HA inhibition and hydrolysis efficiencies reached up to 75, 65 and 72%, respectively, compared to the control groups in the batch wise incubations (Chapter 3). However, in long term CSTR operations, calcium addition did not show a positive effect on hydrolysis inhibition. On the other hand, enzyme addition helped to reverse the negative effect of HA.

    The microbial communities involved in AD were also studied. Chapter 5 and Chapter 6 dealt with microbial community analyses with 16S rRNA next generation sequencing. In Chapter 5, five replicate reactors were monitored during the start-up period. Transient feeding strategy was used to acclimatise anaerobic sludge to efficient cellulose and xylan degradation. During the experiment, Bacteriodales, Clostridiales and Anaerolineales became dominant bacterial populations while, Methanobacteriaceae and Methanospirillaceae were the dominant archaeal populations within the reactors. In Chapter 6, the microbial population dynamics in the presence and absence of HA were monitored. Microbiological analyses showed that the abundance of hydrolytic/fermentative bacterial groups such as Clostridiales, Bacteroidales and Anaerolineales was significantly lowered by the presence of HA. HA also affected the archaeal populations. Mostly hydrogenotrophic methanogens were negatively affected by HA.

    In conclusion, this thesis confirms that HA inhibit the hydrolysis and methanogenesis within both batch incubations and CSTR systems. Microbial populations were also affected by HA. Therefore, hydrolytic enzyme addition can be an option to mitigate HA inhibition and enhance hydrolysis and methanogenesis during conversion of biomass to biogas.

    Fibrillar structures in mixed systems
    Peng, Jinfeng - \ 2016
    Wageningen University. Promotor(en): Erik van der Linden, co-promotor(en): Paul Venema; K.P. Velikov. - Wageningen : Wageningen University - ISBN 9789462578265 - 284
    cellulose - bacteria - fibres - protein isolates - whey - mixtures - emulsions - mechanical properties - cellulose - bacteriën - vezels - eiwitisolaten - wei - mengsels - emulsies - mechanische eigenschappen

    Fibrillar structures are important structuring elements for food products. Understanding the behaviour of fibrillar structures in complex food systems is essential for successful industrial applications. This thesis presents the behaviour of two different fibrillar structures, i.e. whey protein isolate (WPI) fibrils and bacterial cellulose (BC) microfibrils in mixtures under various conditions. The WPI fibrils are prepared from WPI and the BC microfibrils are extracted from commercial available ‘Nata de Coco’ by high-energy de-agglomeration. In Chapter 1, a general introduction is given, where we introduce two different fibrillar structures that were studied in this thesis. Also, the aim and the outline of the thesis are presented. In Chapter 2, 3, 4 and 5, the behaviour of mixtures containing WPI and BC microfibrils under different conditions are investigated. By varying the concentration ratios, pH, NaCl concentration and further applying heating treatment, their physico-chemical properties in mixed solutions, mixed solutions after heating and further heat-induced mixed gels are investigated and characterized at both pH 2 and pH 7. In general, both mixing WPI and BC microfibrils without heating and subsequently applying heating treatment lead to stable and homogeneous mixtures at pH 7, as long as BC microfibril concentration is above a critical value. Microscopic images showed that the WPI aggregates and BC microfibrils co-existed in the system. WPI denatured and aggregated in the mixture in the same way as when it is heated alone. Upon gelation, the WPI and BC microfibrils form a duplex gel consisting of two independent and homogeneous networks spanning the whole system. At pH 2, the WPI and BC microfibrils also form stable and homogeneous mixtures in the liquid state, both before and after heating. Microscopic images showed two fibrillar structures that are uniformly and independently present. Upon gelation at higher WPI concentration, a bi-fibrillar gel is formed consisting of a WPI fibrilllar gel and BC microfibrillar gel that co-exist. In Chapter 6 and 7, the behaviour of WPI fibrils at pH 2 in dispersions containing spheres, i.e. emulsions and polystyrene latex dispersions are studied. When WPI and spheres are both positively charged (i.e. WPI-stabilized emulsion), we observed depletion flocculation and depletion stabilization when the WPI fibril concentration increases. When WPI and the spheres are oppositely charged (i.e. polystyrene latex dispersions), bridging flocculation and steric/electrostatic stabilization were observed at low WPI fibril concentration, followed by depletion flocculation and depletion stabilization upon increasing WPI fibril concentrations. In Chapter 8 the stability of emulsions at pH 2 in the presence of only BC microfibrils and in the presence of both BC microfibrils and WPI fibrils was studied. When only BC microfibrils added at a sufficiently high concentration, the emulsions are stabilized by the presence of a yield stress as generated by the BC network. When both WPI fibrils and BC microfibrils are added to the emulsions, the networks they form behave in the same way, as when they are added to the emulsions separately. The WPI fibrils induced depletion flocculation and stabilization of the emulsions, despite the presence of the BC microfibrils. However, at high enough BC microfibril concentrations, the emulsions can be stabilized against depletion flocculation as induced by the WPI fibrils. The competition between stabilization and/or de-stabilization induced by the BC microfibrils and the WPI fibrils can lead to emulsions with different microstructures and rheological properties. A general discussion on the results obtained in this thesis is presented in Chapter 9, which includes recommendations for further research and concluding remarks.

    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.
    Aqueous foams stabilized by chitin nanocrystals
    Tzoumaki, M. ; Karefyllakis, D. ; Moschakis, T. ; Biliaderis, C.G. ; Scholten, E. - \ 2015
    Soft Matter 11 (2015). - ISSN 1744-683X - p. 6245 - 6253.
    in-water emulsions - pickering emulsions - silica nanoparticles - polymer microrods - fluid interfaces - particles - cellulose - behavior - bubbles - microparticles
    The aim of the present study was to explore the potential use of chitin nanocrystals, as colloidal rod-like particles, to stabilize aqueous foams. Chitin nanocrystals (ChN) were prepared by acid hydrolysis of crude chitin and foams were generated mainly by sonicating the respective dispersions. The foamability of the chitin nanocrystals was evaluated and the resulting foams were assessed for their stability, in terms of foam volume reduction and serum release patterns, during storage. Additionally, the samples were studied with light scattering and optical microscopy in order to explore the bubble size distribution and morphology of the foam. Nanocrystal concentration and charge density was varied to alter the packing of the crystals at the interface. At low concentrations of ChNs, foams were stable against coalescence and disproportionation for a period of three hours, whereas at higher concentrations, the foams were stable for several days. The enhanced stability of foams prepared with ChNs, compared to surfactant-stabilized foams, can be mainly attributed to the irreversible adsorption of the ChNs at the air-water interface, thereby providing Pickering stabilization. Both foam volume and stability of the foam were increased with an increase in ChNs concentration, and at pH values around the chitin's pKa (pH 7.0). Under these conditions, the ChNs show minimal electrostatic repulsion and therefore a higher packing of the nanocrystals is promoted. Moreover, decreased electrostatic repulsion enhances network formation between the ChNs in the aqueous films, thereby providing additional stability by gel formation. Overall, ChNs were proven to be effective in stabilizing foams, and may be useful in the design of Pickering-stabilized food grade foams.
    How Does Alkali Aid Protein Extraction in Green Tea Leaf Residue: A Basis for Integrated Biorefinery of Leaves
    Zhang, C. ; Sanders, J.P.M. ; Xiao, T.T. ; Bruins, M.E. - \ 2015
    PLoS ONE 10 (2015)7. - ISSN 1932-6203
    functional-properties - antioxidant activity - sugar-beet - cell-walls - cellulose - pectins - biomass - acid - degradation - hydrolysis
    Leaf protein can be obtained cost-efficiently by alkaline extraction, but overuse of chemicals and low quality of (denatured) protein limits its application. The research objective was to investigate how alkali aids protein extraction of green tea leaf residue, and use these results for further improvements in alkaline protein biorefinery. Protein extraction yield was studied for correlation to morphology of leaf tissue structure, protein solubility and hydrolysis degree, and yields of non-protein components obtained at various conditions. Alkaline protein extraction was not facilitated by increased solubility or hydrolysis of protein, but positively correlated to leaf tissue disruption. HG pectin, RGII pectin, and organic acids were extracted before protein extraction, which was followed by the extraction of cellulose and hemi-cellulose. RGI pectin and lignin were both linear to protein yield. The yields of these two components were 80% and 25% respectively when 95% protein was extracted, which indicated that RGI pectin is more likely to be the key limitation to leaf protein extraction. An integrated biorefinery was designed based on these results. Introduction
    Analysis of by-product formation and sugar monomerization in sugarcane bagasse pretreated at pilot plant scale: Differences between autohydrolysis, alkaline and acid pretreatment
    Pol, E.C. van der; Bakker, R. ; Zeeland, A.N.T. van; Sanchez Garcia, D. ; Punt, A.M. ; Eggink, G. - \ 2015
    Bioresource Technology 181 (2015). - ISSN 0960-8524 - p. 114 - 123.
    saccharomyces-cerevisiae - degradation-products - wet oxidation - hydrolysis - ethanol - fermentations - cellulose - glucose - biomass
    Sugarcane bagasse is an interesting feedstock for the biobased economy since a large fraction is polymerized sugars. Autohydrolysis, alkaline and acid pretreatment conditions combined with enzyme hydrolysis were used on lignocellulose rich bagasse to acquire monomeric. By-products found after pretreatment included acetic, glycolic and coumaric acid in concentrations up to 40, 21 and 2.5 g/kg dry weight bagasse respectively. Alkaline pretreated material contained up to 45 g/kg bagasse DW of sodium. Acid and autohydrolysis pretreatment results in a furan formation of 14 g/kg and 25 g/kg DW bagasse respectively. Enzyme monomerization efficiencies of pretreated solid material after 72 h were 81% for acid pretreatment, 77% for autohydrolysis and 57% for alkaline pretreatment. Solid material was washed with superheated water to decrease the amount of by-products. Washing decreased organic acid, phenol and furan concentrations in solid material by at least 60%, without a major sugar loss.
    Interactions between Auxin, Microtubules and XTHs Mediate Green Shade- Induced Petiole Elongation in Arabidopsis
    Sasidharan, R. ; Keuskamp, D.H. ; Kooke, R. ; Voesenek, L.A.C.J. ; Pierik, R. - \ 2014
    PLoS ONE 9 (2014)3. - ISSN 1932-6203
    outer epidermal wall - cortical microtubules - plasma-membrane - cell-wall - maize coleoptiles - differential growth - avoidance responses - abiotic stresses - plant-cells - cellulose
    Plants are highly attuned to translating environmental changes to appropriate modifications in growth. Such phenotypic plasticity is observed in dense vegetations, where shading by neighboring plants, triggers rapid unidirectional shoot growth (shade avoidance), such as petiole elongation, which is partly under the control of auxin. This growth is fuelled by cellular expansion requiring cell-wall modification by proteins such as xyloglucan endotransglucosylase/hydrolases (XTHs). Cortical microtubules (cMTs) are highly dynamic cytoskeletal structures that are also implicated in growth regulation. The objective of this study was to investigate the tripartite interaction between auxin, cMTs and XTHs in shade avoidance. Our results indicate a role for cMTs to control rapid petiole elongation in Arabidopsis during shade avoidance. Genetic and pharmacological perturbation of cMTs obliterated shade-induced growth and led to a reduction in XTH activity as well. Furthermore, the cMT disruption repressed the shade-induced expression of a specific set of XTHs. These XTHs were also regulated by the hormone auxin, an important regulator of plant developmental plasticity and also of several shade avoidance responses. Accordingly, the effect of cMT disruption on the shade enhanced XTH expression could be rescued by auxin application. Based on the results we hypothesize that cMTs can mediate petiole elongation during shade avoidance by regulating the expression of cell wall modifying proteins via control of auxin distribution.
    Biorefining of wheat straw using an acetic and formic acid based organosolv fractionation process
    Snelders, J. ; Dornez, E. ; Benjelloun-Mlayah, B. ; Huijgen, W.J.J. ; Wild, P.J. de; Gosselink, R.J.A. ; Gerritsma, J. ; Courtin, C.M. - \ 2014
    Bioresource Technology 156 (2014). - ISSN 0960-8524 - p. 275 - 282.
    xylan-degrading enzymes - enzymatic-hydrolysis - lignocellulosic biomass - pretreatment - lignin - fermentation - residues - hemicellulose - bioethanol - cellulose
    To assess the potential of acetic and formic acid organosolv fractionation of wheat straw as basis of an integral biorefinery concept, detailed knowledge on yield, composition and purity of the obtained streams is needed. Therefore, the process was performed, all fractions extensively characterized and the mass balance studied. Cellulose pulp yield was 48% of straw dry matter, while it was 21% and 27% for the lignin and hemicellulose-rich fractions. Composition analysis showed that 67% of wheat straw xylan and 96% of lignin were solubilized during the process, resulting in cellulose pulp of 63% purity, containing 93% of wheat straw cellulose. The isolated lignin fraction contained 84% of initial lignin and had a purity of 78%. A good part of wheat straw xylan (58%) ended up in the hemicellulose-rich fraction, half of it as monomeric xylose, together with proteins (44%), minerals (69%) and noticeable amounts of acids used during processing.
    Effect of Soluble and Insoluble Fibers within the in Vitro Fermentation of Chicory Root Pulp by Human Gut Bacteria
    Ramasamy, U. ; Venema, K. ; Schols, H.A. ; Gruppen, H. - \ 2014
    Journal of Agricultural and Food Chemistry 62 (2014)28. - ISSN 0021-8561 - p. 6794 - 6802.
    human colonic microbiota - large-intestine - dietary modulation - genomic analysis - system - oligosaccharides - fermentability - metabolism - prebiotics - cellulose
    The aim of this research was to study the in vitro fermentation of chicory root pulp (CRP) and ensiled CRP (ECRP) using human fecal inoculum. Analysis of carbohydrate levels in fermentation digests showed that 51% of all CRP carbohydrates were utilized after 24 h of fermentation. For ECRP, having the same cell wall polysaccharide composition as CRP, but with solubilization of 4 times more of CRP pectin due to ensiling, the fermentation was quicker than with CRP as 11% more carbohydrates were utilized within the first 12 h. The level of fiber utilization for ECRP after 24 h was increased by 8% compared to CRP. This effect on fiber utilization from ECRP seemed to arise from (i) increased levels of soluble pectin fibers (arabinan, homogalacturonan, and galactan) and (ii) ahypothesized more open structure of the remaining cell walls in ECRP, which was more accessible to degradation than the CRP cell wall network. KEYWORDS: chicory root pulp, ensiled chicory root pulp, insoluble
    Influence of water content and drying on the physical structure of native hyaluronan
    Prusova, A. ; Vergeldt, F.J. ; Kucerik, J. - \ 2013
    Carbohydrate Polymers 95 (2013)1. - ISSN 0144-8617 - p. 515 - 521.
    aqueous-solution - hydration structure - tertiary structures - nmr-spectroscopy - dynamics - hydrogels - cellulose - behavior - protein - dsc
    Hydration properties of semi-diluted hyaluronan were studied by means of time domain nuclear magnetic resonance. Based on the transverse proton relaxation times T2, the plasticization of hyaluronan which was precipitated by isopropylalcohol and dried in the oven have been determined at water content 0.4 g of water per g of hyaluronan. Above this water content, the relaxation times increased and levelled off around 0.8 g of water per g of hyaluronan which agrees well with values determined earlier by differential scanning calorimetry and dielectric relaxometry. The freeze dried and oven dried samples showed differences in their physical structure such as glass transition, plasticization concentration and sample topography which influenced their kinetics and mechanisms of hydration. Results confirmed earlier hypothesis that some native biopolymer structures can be easily modified by manipulation of preparation conditions, e.g. drying, giving fractions with specific physicochemical properties without necessity of their chemical modification.
    Structural and water-holding characteristics of untreated and ensiled chicory root pulp
    Ramasamy, U. ; Gruppen, H. ; Schols, H.A. - \ 2013
    Journal of Agricultural and Food Chemistry 61 (2013)25. - ISSN 0021-8561 - p. 6077 - 6085.
    cell-walls - nonstarch polysaccharides - liquid-chromatography - by-products - xyloglucan - cellulose - pectins - fiber - purification - substances
    Cell wall polysaccharides (CWPs) from chicory root pulp (CRP) and the effect of ensiling on CWP structure to reduce the water-holding capacity (WHC) were studied. Sequential extractions of CRP showed that hot water extraction solubilized arabinan-rich pectin and inulin, each representing 6% of all CRP sugars. A significant amount of pectic sugars (46%) rich in uronic acid from CRP was solubilized by chelating agents. Both dilute alkali extraction, which solubilized branched pectin (14% from CRP), and concentrated alkali extraction, which solubilized hemicellulose dominant in yloglucans (2.5%) mostly of the XXXG type and mannan (0.9%), from CRP CWPs seemed to influence the WHC of CRP. Alkali-insoluble residue (39% of CRP sugars) mainly comprised cellulose and some branched pectin (17% from CRP). Ensiling reduced the methyl esterification of pectin, caused degradation of homogalacturonan and rhamnogalacturonan, and possibly modified the xyloglucan, mannan, and glucan network, reducing the WHC from 6 mL/g to 3.4 mL/g.
    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
    The podzol hydrosequence of Itaguare (Sao Paulo, Brazil). 2. Soil organic matter chemistry by pyrolysis-gas chromatography / mass spectrometry
    Buurman, P. ; Vidal-Torrado, P. ; Millani Lopes, J. - \ 2013
    Soil Science Society of America Journal 77 (2013)4. - ISSN 0361-5995 - p. 1307 - 1318.
    gc-ms - horizons - gc/ms - micromorphology - fractions - cellulose - nmr
    A Late Pleistocene to Holocene hydrosequence of podzols in the coastal plain of São Paulo (Brazil), of which the macromorphology was described previously, was investigated by pyrolysis-gas chromatography/mass spectrometry (GC/ MS). Differences in chemical composition of organic matter (OM) coincided very well with the morphological interpretation of these profiles with respect to drainage conditions, origin of OM, and decomposition. OM in B-horizons of poorly-drained profiles has a signature of dissolved organic matter (DOM), while that of well-drained profiles indicates root-derived material. Bands that, according to their morphology, were attributed to DOM have different signature within the profiles, reflecting DOM origin. The EB horizons of poorly-drained profiles show a selective decay of B-horizon material, resulting in a relative accumulation of aliphatics in poorly drained profiles. In the EB horizons of the well-drained profiles, however, significant amounts of microbial products were accumulated and poly-aromatic compounds were the most stable. This has not been described for temperate podzols. Factor analysis suggests that local differences in vegetation are responsible for about 50% of the total chemical variation in pyrolysates, whereas source, transport, and decomposition in the profile account for the other half. The results underline that OM composition of podzol horizons is strongly dependent on hydrological conditions, resulting in divergent soil organic matter (SOM) properties between soils from different landscape contexts. Nonetheless, there is a comprehensible relation between SOM fingerprints of horizons within one profile. Finally, changes in OM composition at horizon transitions provide insight into the podzolization process.
    Promoting chain elongation in mixed culture acidification reactors by addition of ethanol
    Grootscholten, T.I.M. ; Kinsky dal Borgo, F. ; Hamelers, H.V.M. ; Buisman, C.J.N. - \ 2013
    Biomass and Bioenergy 48 (2013). - ISSN 0961-9534 - p. 10 - 16.
    clostridium-kluyveri - liquid fuels - fatty-acids - solid-waste - hydrolysis - digestion - cellulose - biomass
    In this research we investigate a microbial production process to produce medium chain fatty acids (MCFAs) based on the organic fraction of municipal solid waste (OFMSW). In this microbial production process, called chain elongation, bacteria produce medium chain fatty acids (MCFAs) from ethanol and volatile fatty acids (VFAs). MCFAs could be used as new biomass based building blocks for the chemical and fuel industry. The objective of this article is to investigate whether chain elongation can be promoted during acidification of OFMSW by addition of ethanol. The results show that chain elongation can be promoted during acidification of OFMSW by addition of ethanol. However, the hydrolysis rate and the carboxylic acid yield of the OFMSW in reactors with ethanol additions were lower than the hydrolysis rate and the carboxylic acid yield than in reactors without ethanol additions. Further research is required to determine whether a combined chain elongation and acidification reactor or a separated reactor system is more advantageous for MCFA production from OFMSW.
    Effect of cold-induced changes in physical and chemical leaf properties on the resistance of winter triticale (xTriticosecale) to the fungal pathogen Microdochium nivale
    Szechynska-Hebda, M. ; Hebda, M. ; Mierzwinski, D. ; Kuczynska, P. ; Mirek, M. ; Wedzony, M. ; Lammeren, A. van; Karpinski, S. - \ 2013
    Plant Pathology 62 (2013)4. - ISSN 0032-0862 - p. 867 - 878.
    plant-cell walls - disease resistance - wheat spikes - arabidopsis - infection - cellulose - susceptibility - mechanisms - expression
    This study showed that several mechanisms of the basal resistance of winter triticale to Microdochium nivale are cultivar-dependent and can be induced specifically during plant hardening. Experiments and microscopic observations were conducted on triticale cvs Hewo (able to develop resistance after cold treatment) and Magnat (susceptible to infection despite hardening). In cv. Hewo, cold hardening altered the physical and chemical properties of the leaf surface and prevented both adhesion of M. nivale hyphae to the leaves and direct penetration of the epidermis. Cold-induced submicron- and micron-scale roughness on the leaf epidermis resulted in superhydrophobicity, restricting fungal adhesion and growth, while the lower permeability and altered chemical composition of the host cell wall protected against tissue digestion by the fungus. The fungal strategy to access the nutrient resources of resistant hosts is the penetration of leaf tissues through stomata, followed by biotrophic intercellular growth of individual hyphae and the formation of haustoria-like structures within mesophyll cells. In contrast, a destructive necrotrophic fungal lifestyle occurs in susceptible seedlings, despite cold hardening of the plants, with the host epidermis, mesophyll and vascular tissues being digested and becoming disorganized as a result of the low chemical and mechanical stability of the cell wall matrix. This work indicates that specific genetically encoded physical and mechanical properties of the cell wall and leaf tissues that depend on cold hardening are factors that can determine plant resistance against fungal diseases.
    Check title to add to marked list
    << previous | next >>

    Show 20 50 100 records per page

    Please log in to use this service. Login as Wageningen University & Research user or guest user in upper right hand corner of this page.