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.

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    Heterologous expression of Mus musculus immunoresponsive gene 1 (irg1) in Escherichia coli results in itaconate production
    Vuoristo, K.S. ; Mars, A.E. ; Loon, S. ; Orsi, E. ; Eggink, G. ; Sanders, J.P.M. ; Weusthuis, R.A. - \ 2015
    Frontiers in Microbiology 6 (2015). - ISSN 1664-302X
    codon usage frequencies - aspergillus-terreus - acid production - protein expression - niger - host
    Itaconic acid, a C5-dicarboxylic acid, is a potential biobased building block for the polymer industry. It is obtained from the citric acid cycle by decarboxylation of cis-aconitic acid. This reaction is catalyzed by CadA in the native itaconic acid producer Aspergillus terreus. Recently, another enzyme encoded by the mammalian immunoresponsive gene 1 (irg1), was found to decarboxylate cis-aconitate to itaconate in vitro. We show that heterologous expression of irg1 enabled itaconate production in Escherichia coli with production titres up to 560 mg/L.
    Heterologous expression of Gaeumannomyces graminis lipoxygenase in Aspergillus nidulans
    Heshof, R. ; Schayck, J.P. van; Tamayo Ramos, J.A. ; Graaff, L.H. de - \ 2014
    AMB Express 4 (2014). - ISSN 2191-0855 - 6 p.
    niger - protein - biosynthesis - oxylipins - genes
    Aspergillus sp. contain ppo genes coding for Ppo enzymes that produce oxylipins from polyunsaturated fatty acids. These oxylipins function as signal molecules in sporulation and influence the asexual to sexual ratio of Aspergillus sp. Fungi like Aspergillus nidulans and Aspergillus niger contain just ppo genes where the human pathogenic Aspergillus flavus and Aspergillus fumigatus contain ppo genes as well as lipoxygenases. Lipoxygenases catalyze the synthesis of oxylipins and are hypothesized to be involved in quorum-sensing abilities and invading plant tissue. In this study we used A. nidulans WG505 as an expression host to heterologously express Gaeumannomyces graminis lipoxygenase. The presence of the recombinant LOX induced phenotypic changes in A. nidulans transformants. Also, a proteomic analysis of an A. nidulans LOX producing strain indicated that the heterologous protein was degraded before its glycosylation in the secretory pathway. We observed that the presence of LOX induced the specific production of aminopeptidase Y that possibly degrades the G. graminis lipoxygenase intercellularly. Also the presence of the protein thioredoxin reductase suggests that the G. graminis lipoxygenase is actively repressed in A. nidulans.
    A review of the proximate composition and nutritional value of Marula (Sclerocarya birrea subsp. caffra)
    Hiwilepo-Van Hal, P. ; Bille, P.G. ; Verkerk, R. ; Boekel, M.A.J.S. van; Dekker, M. - \ 2014
    Phytochemistry Reviews 13 (2014)4. - ISSN 1568-7767 - p. 881 - 892.
    tropical fruits - food-products - ascorbic-acid - niger - juice
    This review critically evaluated literature on proximate composition and nutritional value of Marula in comparison with other tropical and indigenous fruits in order to identify areas for future research. It was found that nutrients content and processing methods of Marula fruit varied greatly from study to study and according to place of origin, soil, climate, handling, analytical methods used and time that lapsed after harvesting before analysis took place. Marula fruit pulp is reported to have vitamin C content higher than that of most fruits, ranging from 62 mg/100 g to over 400 mg/100 g. Additionally, Marula fruit is reported to have an antioxidant capacity of between 8 and 25 mM, (ascorbic acid equivalents) and a total phenolic content ranging from 7.5 to 24 mg/g dry weight gallic acid equivalent. Marula kernels are also a good source of protein, oil, magnesium, phosphorus and potassium and their oil is used in food preparations. Marula fruits could play a vital role in terms of nutrition to rural community who rely on the usage of the fruits, as they do not have easy access to other sources of nutrients. Recommendation given for future research includes improving Marula fruits juice extraction and yields, investigating the effect of processing and storage on the retention of nutrients such as vitamin C and its antioxidant capacity in processed and unprocessed Marula products and further identifying Marula fruits flavor compounds and their effect on processing and storage.
    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
    Increasing nutrient use efficiency through improved feeding and manure manegement in urban and peri-urban livestock units of a West African city: A scenario analysis
    Diogo, V. ; Schlecht, E. ; Buerkert, A. ; Rufino, M.C. ; Wijk, M.T. van - \ 2013
    Agricultural Systems 114 (2013). - ISSN 0308-521X - p. 64 - 72.
    smallholder farming systems - cycling efficiencies - crop production - diet selection - cattle - niger - resource - sahel - kenya - agriculture
    In many African cities urban and peri-urban agriculture (UPA) plays a major role in creating jobs and contributing to food security. However, many small-scale UPA systems are characterised by excessive nutrient inputs to the livestock unit and poor handling of manure. To assess the impact of improved feeding and manure management on nutrient use efficiency within the cattle unit, simulation modelling was used to compare three typical UPA farm types in Niamey, Niger, that comprised: animal husbandry alone (AH), animal husbandry plus gardening (AH+G), and animal husbandry plus gardening plus millet cultivation (AH+G+M). Improved feeding increased annual body weight gain and milk offtake from cattle and reduced the amount of nitrogen (N) excreted in urine, thereby lowering the risk of N emissions. With improved manure management, dry matter (DM) and nutrients recycled per animal and year, and potentially available for cropping, ranged from 321–690 kg DM, 8–22 kg N, 1.2–2.5 kg phosphorus (P), and 3.0–5.6 kg potassium (K) in AH as well as AH+G+M farms compared to 221–479 kg DM, 5.0–14.0 kg N, 0.7–1.6 kg P, and 2.0–4.0 kg K in AH+G farms. These amounts were up to 2.2-, 2.5-, 1.9- and 1-fold higher than the quantities of DM, N, P and K recycled under current practices. Feeding dairy cattle according to their requirements will enhance milk and meat production; if coupled with regular manure collection and low-cost covering of manure heaps, substantial amounts of nutrients are recycled to cropland and vegetable gardens and environmental pollution is reduced.
    Enzymatic synthesis of b-xylosyl-oligosaccharides by transxylosylation using
    Dilokpimol, A. ; Nakai, H. ; Gotfredsen, C.H. ; Appeldoorn, M.M. ; Baumann, M.J. ; Nakai, N. ; Schols, H.A. ; Hachem, M.A. ; Svensson, B. - \ 2011
    Carbohydrate Research : an international journal 346 (2011)3. - ISSN 0008-6215 - p. 421 - 429.
    alpha-l-arabinofuranosidase - trichoderma-reesei - purification - hydrolysis - expression - proteins - sequence - niger - xlnd - xylooligosaccharides
    Two b-xylosidases of glycoside hydrolase family 3 (GH 3) from Aspergillus nidulans FGSC A4, BxlA and BxlB were produced recombinantly in Pichia pastoris and secreted to the culture supernatants in yields of 16 and 118 mg/L, respectively. BxlA showed about sixfold higher catalytic efficiency (kcat/Km) than BxlB towards para-nitrophenyl b-D-xylopyranoside (pNPX) and b-1,4-xylo-oligosaccharides (degree of polymerisation 2–6). For both enzymes kcat/Km decreased with increasing b-1,4-xylo-oligosaccharide chain length. Using pNPX as donor with 9 monosaccharides, 7 disaccharides and two sugar alcohols as acceptors 18 different b-xylosyl-oligosaccharides were synthesised in 2–36% (BxlA) and 6–66% (BxlB) yields by transxylosylation. BxlA utilised the monosaccharides D-mannose, D-lyxose, D-talose, D-xylose, D-arabinose, L-fucose, D-glucose, D-galactose and D-fructose as acceptors, whereas BxlB used the same except for D-lyxose, D-arabinose and L-fucose. BxlB transxylosylated the disaccharides xylobiose, lactulose, sucrose, lactose and turanose in upto 35% yield, while BxlA gave inferior yields on these acceptors. The regioselectivity was acceptor dependent and primarily involved b-1,4 or 1,6 product linkage formation although minor products with different linkages were also obtained. Five of the 18 transxylosylation products obtained from D-lyxose, D-galactose, turanose and sucrose (two products) as acceptors were novel xylosyl- oligosaccharides, b-D-Xylp-(1?4)-D-Lyxp, b-D-Xylp-(1?6)-D-Galp, b-D-Xylp-(1?4)-a-D-Glcp-(1?3)- b-D-Fruf, b-D-Xylp-(1?4)-a-D-Glcp-(1?2)-b-D-Fruf, and b-D-Xylp-(1?6)-b-D-Fruf-(2?1)-a-D-Glcp, as structure-determined by 2D NMR, indicating that GH3 b-xylosidases are able to transxylosylate a larger variety of carbohydrate acceptors than earlier reported. Furthermore, transxylosylation of certain acceptors resulted in mixtures. Some of these products are also novel, but the structures of the individual products could not be determined.
    Mating, hybridisation and introgression in Lasius ants
    Have, T.M. van der; Pedersen, J.S. ; Boomsma, J.J. - \ 2011
    Myrmecological News 15 (2011). - ISSN 1994-4136 - p. 109 - 115.
    nuptial flights - niger - paternity - populations - evolution - ecology - alienus - fauna
    Recent reviews have shown that hybridisation among ant species is likely to be more common than previously appreciated. but that documented cases of introgression remain rare. After molecular phylogenetic work had shown that European Lasius niger (LINNAEUS, 1758) and L. psammophilus SEIFERT, 1992 (formerly L. alienus (FOERSTER. 1850)) are unlikely to be very closely related, we decided to analyse an old data set confirming the conclusion by PEARSON (1983) that these two ants can indeed form viable hybrids. We show that signatures of introgression can be detected in a Danish site and that interspecific gene-flow is asymmetrical (only from L. niger into L. psammophilus) as inferred previously by Pearson for the southern England site that he studied and from which we also collected data. We compare the observed patterns of hybridisation and introgression in the Danish and British site and infer that overlap in nuptial flights in Denmark may have contributed to the higher frequency of introgressed genes relative to the southern England site where nuptial flights are clearly separated in time. We also report the first mating system data for L. psammophilus. showing that this species has facultative multiple mating of queens similar to L. niger. We suggest that L. psammoplillus-niger introgression may be much more common than previously appreciated, which would explain that European myrmecologists have often found it difficult to distinguish between these species at sites where they occur sympatrically. This would imply that multiple accessible field sites are available to study the molecular details of hybridisation and introgression between two ant species that have variable degrees of sympatiy throughout their distributional ranges
    An evolutionary conserved d-galacturonic acid metabolic pathway operates across filamentous fungi capable of pectin degradation
    Martens-Uzunova, E.S. ; Schaap, P.J. - \ 2008
    Fungal Genetics and Biology 45 (2008)11. - ISSN 1087-1845 - p. 1449 - 1457.
    aspergillus-nidulans mutants - mold hypocrea-jecorina - escherichia-coli - sequence alignment - niger - purification - bacteria - identification - aldolase
    Transcriptome analysis of Aspergillus niger transfer cultures grown on galacturonic acid media identified a highly correlating cluster of four strongly induced hypothetical genes linked with a subset set of genes encoding pectin degrading enzymes. Three of the encoded hypothetical proteins now designated GAAA to GAAC are directly involved in further galacturonic acid catabolism. Functional and biochemical analysis revealed that GAAA is a novel d-galacturonic acid reductase. Two non-allelic Aspergillus nidulans strains unable to utilize galacturonic acid are mutated in orthologs of gaaA and gaaB, respectively. The A. niger gaaA and gaaC genes share a common promoter region. This feature appears to be strictly conserved in the genomes of plant cell wall degrading fungi from subphylum Pezizomycotina. Combined with the presence of homologs of the gaaB gene in the same set of fungi, these strongly suggest that a common d-galacturonic acid utilization pathway is operative in these species
    Aeolian and fluviolacustrine landforms and prehistoric human occupation on a tectonically influenced floodplain margin, the Méma, central Mali
    Makaske, B. ; Vries, E. de; Tainter, J.A. ; McIntosh, R.J. - \ 2007
    Netherlands journal of geosciences 86 (2007)3. - ISSN 0016-7746 - p. 241 - 256.
    eolische afzettingen - geomorfologie - geologische sedimentatie - rivieren - landschap - stroomvlakten - mali - aeolian deposits - geomorphology - geological sedimentation - rivers - landscape - floodplains - mali - niger - holocene - africa
    The Méma is a semi-arid region in central Mali with a rich archaeological heritage indicating the former existence of large urban settlements. The archaeological data suggest millennia of occupation history of the Méma preceding relatively sudden abandonment by the 14th or 15th century AD. Population numbers have remained low since then and today's human presence in the area is sparse and largely mobile. Geomorphologically, the Méma can be characterized as a graben hosting various generations of aeolian landforms and (presently mostly dry) interdunal channels and lakes, linked to the neighbouring Inland Niger Delta floodplain. Given this setting, and the variability of the Sahelian climate, climatic contributions to the region's sudden abandonment are likely. A geomorphological survey of the region, and interpretation of the observed geomorphological record in terms of climatic history, aimed at providing a basis for understanding the intensive occupation and subsequent abandonment of the Méma. The results of this study underscore dramatic Holocene climatic variability, leading to the region's present geomorphological diversity, but also suggest that neotectonic movements constitute an important additional cause of regional desiccation. Both may have encouraged prehistoric people to abandon the Méma after a long period of occupation.
    Nutrient dynamics - wind and water erosion at the village scale in the Sahel
    Visser, S.M. ; Sterk, G. - \ 2007
    Land Degradation and Development 18 (2007)5. - ISSN 1085-3278 - p. 578 - 588.
    west-africa - soil - transport - dust - productivity - environment - sediment - impact - niger - land
    The loss of nutrients by wind erosion is generally attributed to losses by suspension, since suspension selectively removes the finest particles. However, because the main mass of sediment is moved by saltation during an event, the main mass of nutrients is also moved by saltation. Nutrient losses from one field during one wind erosion event can be as high as 73 per cent of the N and 100 per cent of the P needs for crop production. Vegetated areas have a higher dust deposition because of the filtering effect of the vegetation and the reduction of drag forces causing a higher deposition. This refutes the general assumption that deposition of suspended dust is homogeneous for a larger area. In the Sahel, two types of dust can be distinguished, the Harmattan dust is richer in nutrients and regarded as a real input of nutrients. The convectional storm dust has a nutrient content comparable with the nutrient content of the dust fraction of the topsoil and can't be regarded as input of nutrients. From research on nutrient losses by water erosion at the plot scale, it is concluded that nutrient erosion by water can cause serious losses of nutrients. But at the village scale, the losses are considerably smaller than at the plot scale. Measurement and subsequent nutrient budget analyses around the village Dangadé in Burkina Faso indicated that this area is especially vulnerable for wind erosion by saltation transport. This demonstrates that in the Sahelian environment, the effect of wind erosion at the village scale can't be ignored.
    Striga hermonthica seed bank dynamics: process quantification and modelling
    Mourik, T.A. van - \ 2007
    Wageningen : Wageningen University and Research Centre (Tropical Resource Management Papers 92) - ISBN 9789085851295 - 123
    striga hermonthica - parasitic plants - parasitic weeds - weed control - integrated pest management - seed banks - buried seeds - dynamics - sorghum - millets - mali - niger - striga hermonthica - parasitaire planten - parasitaire onkruiden - onkruidbestrijding - geïntegreerde plagenbestrijding - zaadbanken - begraven zaden - dynamica - sorghum - gierst - mali - niger
    Ecology and management of charcoal rot (Macrophomina phaseolina) on cowpea in the Sahel
    Ndiaye, M. - \ 2007
    Wageningen University. Promotor(en): Ariena van Bruggen, co-promotor(en): Aad Termorshuizen. - [S.l.] : S.n. - ISBN 9789085046646 - 114
    macrophomina phaseolina - vigna unguiculata - vignabonen - plantenziekten - plantenziekteverwekkende schimmels - geïntegreerde plagenbestrijding - teeltsystemen - compost - biologische bestrijding - sahel - niger - macrophomina phaseolina - vigna unguiculata - cowpeas - plant diseases - plant pathogenic fungi - integrated pest management - cropping systems - composts - biological control - sahel - niger
    Keywords: Senegal/Niger/rotation/millet/isolate characterization/fonio/compost amendment / bioagent/ Clonostachysrosea /solarization

    Cowpea ( Vignaunguiculata Walp.) is the most important pulse crop in theSahelwith nearly 12.5 million hectares per year and is a valuable source of protein for human and animal nutrition. The most limiting factors for crop growth in the Sahelian zone of West Africa are water and nutrient stress. The average cowpea yields in farmers' fields are low (0.2-0.5 ton/ha) and charcoal rot causes on average a yield loss of 10%, which is equivalent to 30.000 tons cowpea - an estimated value of $146 million for Niger and Senegal alone.Disease resistant or tolerant cultivars of cowpea against M . phaseolina are the most efficient control measures but such cultivars are not yet available. Solarization, addition of organic matter, maintenance of high soil moisture, fumigation and use of biocontrol agents have shown to be potential methods for control of soilborne pathogens.The objectives of the thesis is: 1)to characterize cowpea isolates of Macrophomina phaseolina prevalent in the different cowpea cropping systems in Niger and Senegal with respect to culture characteristics and host range; 2) to determine effects of rotation of cowpea with fonio and millet on M. phaseolina disease of cowpea, and production and survival of microsclerotia in soil; 3) to study the effects of compost and a biocontrol agent on M. phaseolina and charcoal rot on cowpea; 4) to study the effects of solarization alone or in combination with organic residues on M. phaseolina and charcoal rot on cowpea.

    Macrophominaphaseolina causes heavy yield loss to cowpea ( Vignaunguiculata ) grown in different cropping systems in the Sahel region ofAfrica. It was not known if cropping systems could influence physiological, genetic and pathogenic characteristics of M. phaseolina isolates. This study therefore aimed to analyze the population structure of M . phaseolina associated with three cropping systems in theSahel. Isolates were collected from soil and infected tissues of different cropping systems in Senegal and Niger and their growth potential at different temperatures, their morphology on PDA medium, their virulence on three cowpea cultivars and sequence analysis of the ITS (internal transcribed spacer) region of the nuclear ribosomal DNA gene studied.Isolates of M. phaseolina differed to a limited extent in temperature optimum, genetic make-up, and pathogenicity to cereal crops. The grouping according to physiological and genetic traits did not coincide with that based on pathogenicity. However, for the first time, we showed some specialization in pathogenicity to cereal crops except fonio ( Digitaria exilis )) for isolates obtained from fields grown to millet next to cowpea.

    Field observations and invitro studies indicated that fonio is a non-host to M. phaseolina , and millet a poor host, respectively. The influence of continuous cropping of these crops on soil inoculum density of M.phaseolinawas studied under field conditions. The data showed thatfonio was not infected by M. phaseolina , while the root systems of millet had low densities of microsclerotia. Cowpea yielded significantly more hay and pods after 3 years of fonio than after 3 years of millet. We conclude that rotation of cowpea with a gramineous crop may lead to a relatively fast decline of inoculum density. In the case of a high inoculum density, fonio can be grown for three years to reduce M . phaseolina densities in soil.

    A field experiment was conducted on the effect of compost on soil inoculum and symptom severity of charcoal rot. The experiment was carried out in naturally infested farmers' fields. The effect of 3 or 6 tons of compost and of 6 tons of compost supplemented with 50 kg NPK fertilizer ha -1 , applied in planting holes, on charcoal rot was assessed for three consecutive years. Besides, the combined effects of 3 tons of compost ha -1 and the biocontrol agent Clonostachysrosea (10 8 CFU's per g compost) on charcoal rot development and cowpea production were investigated. Our results indicated that in Sahelian sandy soil good control and substantial increase of cowpea yield can be achieved by soil amendment with 6 tons of compost ha -1 . An even greater yield increase is achieved by soil amendment with 6 tons of compost and 50 kg NPK ha -1 or 3 tons ha -1 of compost augmented by C.rosea .

    The combined effects of soil solarization and amendment with millet residues and paunch contents on the survival of M . phaseolina and development of charcoal rot of cowpea were assessed in a naturally infested soil.In amended plots, solarization increased the soil temperature to 50°C for at least 4 h day -1 during June, leading to a significant reduction of soil inoculum of M . phaseolina by 44%. Paunch amendment (3 tons ha -1 ) caused 66% reduction of initial inoculum in the solar-heated plots while millet amendment did not enhance microsclerotia reduction in solarized plots. These observations demonstrated that under conditions where solarization alone does not provide sufficient control, the combination with organic amendments improves yields and reduces infection by M . phaseolina . High-N containing amendments may be most effective, such as the paunch used in this study. Solarization as well as application and incorporation of millet residues or paunch content in moistened soil can double cowpea production in poor, naturally infested soil of the Sahelian zone and contribute to the management of paunch waste from slaughter houses in big cities.

    In conclusion the study indicated that M . phaseolinaisolates from different cropping systems in theSahelvary with respect to virulence and ability to cause infection on crop species and cultivars.For the first time we found isolates of C . rosea in theSahelthat are efficient at controlling M . phaseolina . In addition we showed that including fonio in the rotation scheme of cowpea and millet, adding millet residues or paunch contents with or without solar heating and application of 3 tons ha -1 of compost augmented with C . rosea reduced charcoal rot disease and increased cowpea yield. These methods can be integrated intodifferent combinations according to local conditions for managing charcoal rot.
    Mode of action of xylogalacturonan hydrolase towards xylogalacturonan and xylogalacturonan oligosaccharides
    Zandleven, J.S. ; Beldman, G. ; Bosveld, M. ; Benen, J.A.E. ; Voragen, A.G.J. - \ 2005
    Biochemical Journal 387 (2005)3. - ISSN 0264-6021 - p. 719 - 725.
    degrade xylogalacturonan - aspergillus-aculeatus - glycoside hydrolases - exopolygalacturonase - oligogalacturonides - classification - purification - enzymes - niger
    XGH (xylogalacturonan hydrolase; GH 28) is an enzyme that is capable of degrading XGA (xylogalacturonan), which is a polymer of ¿-D-galacturonic acid, highly substituted with ß-D-xylose. XGA is present in cell walls of various plants and exudates, such as gum tragacanth. XGA oligosaccharides were derived from an XGH digestion of gum tragacanth, then fractionated, and analysed for their sugar composition and structure by matrix-assisted laser-desorption ionization-time-of-flight MS and nanospray MS. Several oligosaccharides from XGA were identified with different galacturonic acid/xylose ratios including five oligosaccharide isomers. Although XGH can act as an endo-enzyme, product-progression profiling showed that the disaccharide GalAXyl was predominantly produced from XGA by XGH, which indicated also an exolytic action. The latter was further supported by degradation studies of purified oligosaccharide GalA4Xyl3. It was shown that XGH acted from the non-reducing end towards the reducing end of this oligosaccharide, and showed the processive character of XGH. The results from this study further show that although XGH prefers to act between two xylosidated GalA units, it tolerates unsubstituted GalA units in its - 1 and + 1 subsites.
    Nutrient losses by wind and water, measurements and modelling
    Visser, S.M. ; Stroosnijder, L. ; Chardon, W.J. - \ 2005
    Catena 63 (2005)1. - ISSN 0341-8162 - p. 1 - 22.
    northern burkina-faso - sediment transport - farming systems - erosion - soil - productivity - balances - fields - flows - niger
    In the Sahelian zone of West-Africa, erosion by both wind and water causes a serious decline in fertility of the already low fertile soils. Despite the fact that the flow of nutrients has been intensively investigated by the use of nutrient balances, little attention has been paid to the contribution of the soil erosion to the nutrient balance. Two physically based models (WEPS and EUROSEM, both written in PCRaster) were extended with nutrient modules to investigate the role of wind and water erosion in tire loss and gain of nutrients at the scale of a Sabetian field. The models are applied at three geomorphic units in the Katchari catchment in northern Burkina Faso. WEPS can predict spatial patterns of erosion and deposition due to wind-blown particle transport. Depending on wind direction, crusting and vegetation cover net erosion or deposition can occur. When erosion occurs considerable amounts of nutrients are lost, but when deposition occurs, most of these nutrients may be regained. Soil loss by water erosion is closely related to the crust type present, which regulates infiltration and thus runoff. Nutrient losses by water erosion are small compared with those by wind erosion, but are forever lost for the area. Sediment transport by wind in saltation mode results in the largest soil and nutrient loss at the time scale of an event. (c) 2005 Elsevier B.V. All rights reserved.
    Wind erosion modelling in a Sahelian environment
    Faye-Visser, S.M. ; Sterk, G. ; Karssenberg, D. - \ 2005
    Environmental Modelling & Software 20 (2005)1. - ISSN 1364-8152 - p. 69 - 84.
    crop residue - soil - transport - vegetation - africa - niger
    In the Sahel field observations of wind-blown mass transport often show considerable spatial variation related to the spatial variation of the wind erosion controlling parameters, e.g. soil crust and vegetation cover. A model, used to predict spatial variation in wind erosion and deposition is a useful tool in the implementation of wind erosion control measures in the Sahel. The aim of this paper was to test two existing wind erosion models on spatial predictions of aeolian mass transport for Sahelian conditions. Field data from Burkina Faso were used to test an empirical (RWEQ) and a deterministic (WEPS) model. The revised wind erosion equation (RWEQ) poorly predicted maximum mass transport and so spatial predictions of mass transport were underestimated. Major constraints of RWEQ for application in the Sahel were the required non-eroding boundary and the fact that RWEQ assumes a more or less homogeneous field. It was concluded that RWEQ in its current state was not suitable for application in a Sahelian environment. With the correct roughness length (Z0), wind erosion prediction system (WEPS) correctly predicted friction velocity and initiation and cessation of mass transport. Furthermore, the model gave a reasonable prediction of the spatial distribution of mass transport at the research sites. It was concluded that WEPS in PCRaster is suitable for prediction of wind erosion in a Sahelian environment. A constraint of WEPS in PCRaster is that WEPS' predictions of spatial variation in sediment transport are closely linked to the spatial variation in the input parameters. A good estimation of the spatial variation of the input parameters was required. Obtaining these might be an expensive exercise and could make its use in the Sahel difficult
    Farmers' perceptions of the role of scattered vegetation in wind erosion control on arable land in Burkina Faso
    Leenders, J.K. ; Faye-Visser, S.M. ; Stroosnijder, L. - \ 2005
    Land Degradation and Development 16 (2005)4. - ISSN 1085-3278 - p. 327 - 337.
    west-africa - niger - sahel - soil - system - water
    This paper describes the results of a survey on farmers' perceptions of the effect of woody natural vegetation on wind erosion. Sixty farmers were interviewed in three villages in northern Burkina Faso. The farmers mentioned that the presence of woody vegetation between the crops could benefit yield, but feared competition between the natural vegetation and the crop. Vegetation in a field was considered to increase deposition and decrease erosion on that field. The most important vegetative characteristics that affect wind erosion were, according to the farmers, vegetation's shape, porosity, flexibility and arrangement of the vegetation in the field. At present, most farmers do not apply this knowledge to the management of the natural woody vegetation on their fields
    A new black Aspergillus species, A. vadensis, is a promising host for homologous and heterologous protein production
    Vries, R.P. de; Burgers, K. ; Vondervoort, P.J.I. van de; Frisvad, J.C. ; Samson, R.A. ; Visser, J. - \ 2004
    Applied and Environmental Microbiology 70 (2004)7. - ISSN 0099-2240 - p. 3954 - 3959.
    filamentous fungi - niger - acid
    A new species of the group of black aspergilli, Aspergillus vadensis, was analyzed for its potential as a host for homologous and heterologous protein production. Unlike the other black aspergilli, this strain does not acidify the culture medium when nitrate is the nitrogen source and only produces very low levels of extracellular proteases, mainly serine metalloproteases. The stability of A. tubingensis feruloyl esterase A (FaeA) was compared upon production in wild-type A. vadensis, A. tubingensis, and an A. niger strain in which the three main protease-encoding genes were disrupted. The production of FaeA in A. vadensis resulted in larger amounts of intact protein than production in A. tubingensis and was similar to production in an A. niger protease disruptant, confirming in vivo the low proteolytic activity of A. vadensis. The protoplast formation and transformation efficiencies of A. vadensis were much higher than those of A. niger. These characteristics make A. vadensis a very promising candidate for homologous, and possibly heterologous, protein production.
    Spatial variation in wind-blown sediment transport in geomorphic units in northern Burkina Faso using geostatistical mapping
    Visser, S.M. ; Sterk, G. ; Snepvangers, J.J.J.C. - \ 2004
    Geoderma 120 (2004)1-2. - ISSN 0016-7061 - p. 95 - 107.
    vertical-distribution - soil properties - fields - africa - niger
    Due to rapid population growth, farmers in northern Burkina Faso have started to cultivate areas less suitable for agricultural production. In fields, situated at various geomorphologic settings, erodibility is highly variable resulting in variable wind-blown sediment fluxes. Furthermore, at a field scale, observations of wind-blown mass transport often show spatial variation. This study examines the mass transport rates in three main geomorphic units in northern Burkina Faso and the spatial variation in mass transport in a single geomorphic unit. In the 2001 rainy season, wind-blown mass transport was measured on fields in the valley and on the dune and on a degraded plot in the Katchari catchment. Differences in total mass transport between geomorphic units are related to sediment availability in and around the research plots. Geostatistical theory was applied to produce event-based maps of mass transport by stochastically simulating the spatial correlation structure. The conditionally simulated maps showed large spatial variation in mass transport. It is concluded that, in the Sahelian region of northern Burkina Faso, it will be useful to distinguish erosion and deposition areas in the field. So to be able to deal with spatial variation, a wind erosion model suitable for the Sahelian situation should at least have a spatial component. Furthermore, differences in intensity of sediment transport between geomorphic units indicate that the user should have information about the geomorphic settings of a field to be able to set the boundary conditions
    Polyol accumulation by Aspergillus oryzae at low water activity in solid-state fermentation
    Ruijter, G.J.G. ; Visser, J. ; Rinzema, A. - \ 2004
    Microbiology 150 (2004). - ISSN 1350-0872 - p. 1095 - 1101.
    d-arabitol dehydrogenase - saccharomyces-cerevisiae - hyperosmotic stress - candida-albicans - glycerol - nidulans - pathway - growth - niger - expression
    Polyol accumulation and metabolism were examined in Aspergillus oryzae cultured on whole wheat grains or on wheat dough as a model for solid-state culture. In solid-state fermentation (SSF), water activity (a(w)) is typically low resulting in osmotic stress. In addition to a high level of mannitol, which is always present in the cells, A. oryzae accumulated high concentrations of glycerol, erythritol and arabitol at relatively low a(w) (0(.)96-0(.)97) in SSF. Accumulation of such a mixture of polyols is rather unusual and might be typical for SSF. A. oryzae mycelium accumulating various polyols at low aw contained at least four distinct polyol dehydrogenases with highest activities toward glycerol, erythritol, D-arabitol and mannitol. NADP(+)-dependent glycerol dehydrogenase activity correlated very well with glycerol accumulation. A similar correlation was observed for erythritol and NADP(+)-erythritol dehydrogenase suggesting that NADP(+)-dependent glycerol and erythritol dehydrogenases are involved in biosynthesis of glycerol and erythritol, respectively, and that these enzymes are induced by osmotic stress.
    Wind erosion in a semiarid agricultural area of Spain: the WELSONS project
    Gomes, L. ; Arrue, J.L. ; Lopez, M.V. ; Sterk, G. ; Richard, D. ; Gracia, R. ; Sabre, M. ; Gaudichet, A. ; Frangi, J.P. - \ 2003
    Catena 52 (2003). - ISSN 0341-8162 - p. 235 - 256.
    atmospheric boundary-layer - size distribution - dust production - soil - transport - emission - sediment - tillage - aragon - niger
    The co-ordinated European research project Wind Erosion and Loss of SOil Nutrients in semiarid Spain (WELSONS) was carried out from 1996 to 1999 to understand and predict the potential impacts of land-use change and management on soil degradation by wind erosion on agricultural land in Central Aragon, a semiarid desertification-threatened region in NE Spain. This paper gives a description of the project's experimental approach and an overview of the main results regarding the effects of agricultural practices (i.e. conventional, CT, versus reduced tillage, RT) on surface conditions affecting wind erosion, the mobilisation of soil particles in the saltation layer and the atmospheric emission of fine dust into the suspension layer. The characterisation of the soil surface showed that soil erodibility by wind under RT was lower than that under CT. Though strong Cierzo wind events occurred during the experimental period, only a limited amount of material was available for wind erosion mainly due to soil crusting, a common feature in the area. In spite of this, saltation transport flux was measured at CT plots for different erosion episodes. Also, significant vertical emission of dust was observed only in the CT plot. Finally, the sandblasting efficiency calculated in the present experiment could be interpreted as the result of a higher binding energy for the particles of the silt loam experimental soil compared to soils with a lighter texture.
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