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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    The fatter the better : selecting microalgae cells for outdoor lipid production
    Dominguez Teles, I. - \ 2016
    Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Maria Barbosa; Dorinde Kleinegris. - Wageningen : Wageningen University - ISBN 9789462578821 - 164
    algae - chlorococcum - lipids - lipogenesis - fat - production - phenotypes - inoculum - diameter - cells - sorting - algen - chlorococcum - lipiden - lipogenese - vet - productie - fenotypen - entstof - diameter - cellen - sorteren

    In chapter 1 we introduce microalgae, photosynthetic microorganisms with potential to replace commodities (such as food, feed, chemicals and fuels). Production costs are still high, reason why microalgae are still only economically feasible for niche markets. We suggest to borrow the concept of plant domestication to select industrial microalgae cells. Two approaches can be successfully used to domesticate microalgae: adaptive laboratory evolution (ALE) and fluorescence assisted cell sorting (FACS). ALE takes advantage of the natural adaptability of microorganisms to different environments, while FACS actually select cells with specific phenotypes. This thesis aimed to select cells of Chlorococcum littorale with improved phenotypes, assuming that these cells could establish new populations with increased industrial performance.

    In Chapter 2 we wanted to know what happened during time to biomass and lipid productivities of Chlorococcum littorale repeatedly subjected to N-starvation. We tested 2 different cycles of N-starvation, short (6 days) and long (12 days). Short cycles didn’t affect lipid productivity, highlighting the potential of C. littorale to be produced in semi-continuous cultivation. Repeated cycles of N-starvation could have caused adaptations of the strain. Hence, we also discussed the implications of using repeated N-starvation for adaptive laboratory evolution (ALE) experiments. Chapter 3 introduces a method to detect and to select microalgae cells with increased lipid content. The method requires only the fluorescence dye Bodipy505/515 dissolved in ethanol, and the method was designed to maintain cellular viability so the cells could be used to produce new inoculum. In chapter 4 we evaluated a question that emerged while deciding which criteria to use to sort lipid-rich cells: does cellular size affects lipid productivity of C. littorale? We hypothesized that cells with different diameters have different division rates, which could affect lipid productivity. Therefore, we assessed the influence of cell diameter, as a sorting parameter, on both biomass and lipid productivity of Chlorococcum littorale (comparing populations before and after sorting, based on different diameters). Results showed that the size of vegetative cells doesn’t affect the lipid productivity of C. littorale. In chapter 5 we present a strategy to sort cells of C. littorale with increased TAG productivity using the method developed at chapter 3. Both the original and the sorted population with the highest lipid productivity (namely, S5) were compared under simulated Dutch summer conditions. The results confirmed our data from experiments done under continuous light: S5 showed a double TAG productivity. Our results showed also that the selected phenotype was stable (1.5 year after sorting) and with potential to be used under industrial conditions. In chapter 6 we extrapolated our results (indoor and outdoor) to other climate conditions. We ran simulations changing the light conditions to four different locations worldwide (the Netherlands, Norway, Brazil and Spain) to estimate both biomass and TAG productivities. Results indicated that biomass yields were reduced at locations with higher light intensities (Brazil/Spain) when compared with locations with lower light intensities (Norway/Netherlands). Hence, the choice of location should not be based on light intensity, but on how stable irradiation is. Chapter 7 is the general discussion of the thesis, demonstrating that both ALE and FACS are effective approaches to select industrial microalgae cells. We also present our view on how ALE and FACS could further improve microalgae strains for industry.

    Loofresistentie tegen Phytophthora infestans in aardappel : effecten van isolaatkeuze en proefontwerp op resistentiecijfers
    Kessel, G.J.T. ; Bosch, G.B.M. van den; Forch, M.G. ; Evenhuis, B. ; Flier, W.G. - \ 2010
    Wageningen : Plant Research International, Business Unit Biointeracties en Plantgezondheid (Rapport / Plant Research International 358) - 34
    solanum tuberosum - aardappelen - phytophthora infestans - ziekteresistentie - rassen (planten) - rassenproeven - entstof - solanum tuberosum - potatoes - phytophthora infestans - disease resistance - varieties - variety trials - inoculum
    Gedurende de periode 2002 tot en met 2004 werden veld- en laboratoriumproven uitgevoerd naar de effecten van de toetsmethode en isolaatkeuze op het resulterende Phytophthoraloofresisentiecijfer voor 30 economisch belangrijke rassen in nederland. Twee methodieken, de CGO methode en een alternatieve methode, werden vergeleken. Daarnaast werden de effecten van drie verschllende inocula die in meer of mindere mate representatief waren voor de Nederlandse P. infestans populatie vergeleken.
    Veldresistentie en bemonsteringsmethode van wratziekte (Synchytrium endobioticum)
    Lamers, J.G. ; Been, T.H. ; Bonants, P.J.M. ; Gent-Pelzer, M.P.E. van; Wander, J.G.N. - \ 2007
    synchytrium endobioticum - entstof - bemonsteren - plaagresistentie - synchytrium endobioticum - inoculum - sampling - pest resistance
    Vraag is aan welk niveau van veldresistentie voldaan moet worden om ook in de toekomst de vermeerdering van S. endobioticum en daarmee verspreiding van inoculum tegen te gaan. Bovendien is een goede bemonsteringsmethode belangrijk. De Hendrickx Centrifuge geeft goede uitslagen, maar de bemonsteringstechniek is nog niet onderzocht
    Mycorrhizaschimmels: een rol in gewasbescherming?; thema bodemweerbaarheid
    Baar, J. - \ 2005
    Gewasbescherming 36 (2005)5. - ISSN 0166-6495 - p. 222 - 224.
    gewasbescherming - mycorrhizaschimmels - ectomycorrhiza - vesiculair-arbusculaire mycorrhizae - wortels - bodemschimmels - symbiose - worteloppervlak - plantenziekteverwekkers - entstof - plant protection - mycorrhizal fungi - ectomycorrhizas - vesicular arbuscular mycorrhizas - roots - soil fungi - symbiosis - rhizoplane - plant pathogens - inoculum
    In de grond kunnen bij planten specifieke bodemschimmels voorkomen. Dit zijn de zogeheten mycorrhizaschimmels. Kenmerkend voor mycorrhizaschimmels is dat deze schimmels met planten in een gebalanceerde symbiose leven. Van zo'n symbiose hebben zowel de planten als de schimmels profijt. In dit artikel wordt ingegaan op de achtergrond van de twee belangrijkste groepen mycorrhizaschimmels, de ecto- en arbusculaire mycorrhizaschimmels, en hun mogelijke rol in de gewasbescherming
    Dormancy, activation and viability of Rhizopus oligosporus sporangiospores
    Thanh, N.V. - \ 2004
    Wageningen University. Promotor(en): Frans Rombouts; [No Value] Tran Phuoc Duong, co-promotor(en): Rob Nout. - Wageningen : s.n. - ISBN 9789085040989 - 114
    rhizopus microsporus - schimmelsporen - sporangia - slaaptoestand - levensvatbaarheid - entstof - zuursels - aminozuren - tempé - rhizopus microsporus - fungal spores - sporangia - dormancy - viability - inoculum - starters - amino acids - tempeh
    Biological nitrogen fixation of soybean in acid soils of Sumatra, Indonesia
    Waluyo, S.H. - \ 2000
    Agricultural University. Promotor(en): W.M. de Vos; L. 't Mannetje; L.T. An. - S.l. : S.n. - ISBN 9789058082954 - 151
    glycine max - sojabonen - bodembiologie - stikstoffixatie - stikstofbindende bacteriën - rhizobium - bradyrhizobium - inoculatie - entstof - biochemische technieken - dna-fingerprinting - stamverschillen - stammen (biologisch) - zaadbehandeling - omhullen - zure gronden - bodemaciditeit - bekalking - sumatra - indonesië - glycine max - soyabeans - soil biology - nitrogen fixation - nitrogen fixing bacteria - rhizobium - bradyrhizobium - inoculation - inoculum - biochemical techniques - dna fingerprinting - strain differences - strains - seed treatment - pelleting - acid soils - soil acidity - liming - sumatra - indonesia

    The aim of this study is to improve soybean cultivation in transmigration areas, especially in Sitiung, West Sumatra. However, these soils are very acid, and have a high P-fixing capacity. To reduce the amounts of fertilisers, normally 5 - 7 ton lime ha -1 and 100 kg P as TSP, seed, pelleted with lime (60 kg ha -1 ) and TSP (10 kg ha -1 ), was introduced. In this way only 2 ton lime ha -1 are required.

    Soybean can fix nitrogen (BNF) in symbiosis with ( Brady ) Rhizobium bacteria. However, these acid soils in general, have low numbers of ( Brady ) Rhizobium . By inoculating the soils with ( Brady ) Rhizobium , BNF of soybean, and yield, were considerably improved.

    A study was made of the indigenous ( Brady ) Rhizobium population in view of the following:

      Although at the beginning the numbers may be low, by repeated soybean cultivation, the numbers will increase, and they may interfere with inoculation of effective ( Brady ) Rhizobium strains.These indigenous ( Brady ) Rhizobium are adapted to local stress conditions, and they may be useful for the improvement of strains, to be used as inoculants.

    Using molecular techniques, indigenous strains derived from soil samples from old soybean areas (Java) and from new soybean areas (Sumatra) were classified in more detail. Most likely B. japonicum is the dominant strain in Java while in Sumatra B. elkanii is more present. A Sinorhizobium fredii -like strain was isolated from one soil sample from Java.

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