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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    Cultivation of microalgae in a high irradiance area
    Cuaresma, M. - \ 2011
    Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Marcel Janssen. - [S.l.] : S.n. - ISBN 9789085859543 - 197
    algen - algenteelt - bestraling - chlorella sorokiniana - fotobioreactoren - klimaatfactoren - algae - algae culture - irradiation - chlorella sorokiniana - photobioreactors - climatic factors

    Microalgae are a promising source of high-value products (i.e. carotenoids, ω-3 fatty acids), as well as feedstocks for food, bulk chemicals and biofuels. Industrial production is, however, still limited because the technology needs further development. One of the main bottlenecks is the low efficiency of sunlight usage -the main substrate for growth- achieved under outdoor conditions.
    Locations with high irradiances, and moderate temperatures, along the year are considered optimal for microalgae production. However, an excess of sunlight can also be negative and the cells can be damaged. Under these conditions, the resulting photosynthetic efficiency is low, leading to a low biomass productivity. In this sense, maximization of photosynthetic efficiency in areas with much sunlight is required for commercial purposes. In this Thesis, the effects of simulated winter and summer sunlight conditions on the production of microalgae are evaluated. It is proven that photosynthetic efficiency can be highly improved via the light dilution effect. The injurious effects of excessive light are minimized and/or avoided since a lower amount of light is received per cell when photobioreactors are placed vertically. The production of microalgae in locations with much sunlight should be thus considered.

    AlgaePARC : Algae Production and Research Center
    Wijffels, R.H. - \ 2011
    biobased economy - algenteelt - teeltsystemen - fotobioreactoren - proefstations - biobased economy - algae culture - cropping systems - photobioreactors - experimental stations
    Poster met informatie over de opzet van het AlgaePARC in 2011.
    AlgaePARC : translating research into applications
    Barbosa, Maria - \ 2011
    biobased economy - algae - algae culture - economic viability - experimental design - photobioreactors - research projects
    Effects of shear stress on the microalgae Chaetoceros muelleri
    Michels, M.H.A. ; Goot, A.J. van der; Norsker, N.H. ; Wijffels, R.H. - \ 2010
    Bioprocess and Biosystems Engineering 33 (2010)8. - ISSN 1615-7591 - p. 921 - 927.
    flow filtration systems - small-scale shear - dinoflagellate bioluminescence - phaeodactylum-tricornutum - hydrodynamic stress - cell-suspensions - photobioreactors - cultures - growth - biotechnology
    The effect of shear stress on the viability of Chaetoceros muelleri was studied using a combination of a rheometer and dedicated shearing devices. Different levels of shear stress were applied by varying the shear rates and the medium viscosities. It was possible to quantify the effect of shear stress over a wide range, whilst preserving laminar flow conditions through the use of a thickening agent. The threshold value at which the viability of algae was negatively influenced was between 1 and 1.3 Pa. Beyond the threshold value the viability decreased suddenly to values between 52 and 66%. The effect of shear stress was almost time independent compared to normal microalgae cultivation times. The main shear stress effect was obtained within 1 min, with a secondary effect of up to 8 min.
    Towards high productivities of microalgae in photobioreactors
    Bosma, R. - \ 2010
    Wageningen University. Promotor(en): Rene Wijffels; Hans Tramper, co-promotor(en): Marian Vermue. - [S.l. : S.n. - ISBN 9789085855590 - 133
    bioreactoren - algen - fotosynthese - licht - lichtregiem - oogsten - screenen - stammen (biologisch) - ultrageluid - onderwijs - lesmaterialen - fotobioreactoren - bioreactors - algae - photosynthesis - light - light regime - harvesting - screening - strains - ultrasound - education - teaching materials - photobioreactors
    The biodiversity of microalgae is enormous and they represent an almost untapped source of unique algae products. Presently, there is a niche market for high-value algal products (e.g. carotenoids and fatty acids). To make commercial production of low-value bulk products possible, still many bottlenecks should be solved. This thesis addresses several of these bottlenecks.
    Based on research on the light conversion by the microalgae, a model was developed that predicts the minimal and maximal productivity of the microalgae in a photobioreactor. In addition, a screening method was developed for fast determination of the growth rate of microalgae. This method can be used to optimize the growth medium as well as to optimize cultivation conditions. We used this method to determine the growth inhibiting effects of free fatty acids on a microalga. In addition, the application of ultrasound as harvesting process for microalgae was investigated. It was found that ultrasound could indeed be used to harvest microalgae, but that this process was commercially only feasible for special applications on small scale. Because algal technology is a relatively new research field, learning materials should be developed for appropriate education in this field. This thesis describes the development of a practical in which third year BSc students learn how to cultivate microalgae and to develop a production strategy to achieve as much ß-carotene production as possible using these algae. Finally, the research described above is evaluated and further research strategies are identified to push microalgal technology ahead and to achieve higher productivity of microalgae in photobioreactors in the future.

    The green solar collector: optimization of microalgal areal productivity
    Zijffers, J.F. - \ 2009
    Wageningen University. Promotor(en): Rene Wijffels; Hans Tramper, co-promotor(en): Marcel Janssen. - [S.l.] : S.n. - ISBN 9789085853015 - 156
    algen - algenteelt - bioreactoren - zonnestraling - chlorella sorokiniana - ontwerp - fotobioreactoren - procesontwerp - algae - algae culture - bioreactors - solar radiation - chlorella sorokiniana - design - photobioreactors - process design
    De Groene Zonnecollector (GZC) is een fotobioreactor die is ontworpen voor efficiënte teelt van microalgen op zonlicht. De zon wordt gevolgd door lenzen die het zonlicht op zogenaamde light guides focussen en waarin het licht reflecteerd en naar de algen geleid wordt. Ray-tracing simulaties laten zien dat bij een hogere zonnestand het zonlicht efficient wordt ingevangen en met een lagere intensiteit aan de algen wordt aangeboden. Deze vermindering van de intensiteit van zonlicht resulteert in hogere opbrengsten, als de bijbehorende biomassa concentratie en lichtweg verder is geoptimaliseerd. Een lage biomassa concentratie zal leiden tot grote reactorvolumes. Hoge biomassa dichtheden hebben dan ook de voorkeur. Echter, wanneer hoge biomassa concentraties worden gecombineerd met een grote lichtweg, dan is de gemiddelde lichtintensiteit in de fotobioreactor te laag. Dit zal leiden tot een geringe specifieke groeisnelheid en door de energiebehoefte voor onderhoud zal dit resulteren in een verlaging van de productiviteit.
    Hydrodynamic stress and lethal events in sparged microalgae cultures
    Barbosa, M.J. ; Albrecht, M. ; Wijffels, R.H. - \ 2003
    Biotechnology and Bioengineering 83 (2003)1. - ISSN 0006-3592 - p. 112 - 120.
    dunaliella-tertiolecta - shear sensitivity - light/dark cycles - insect cells - bioreactors - photobioreactors - efficiency
    The effect of high superficial gas velocities in continuous and batch cultures of the strains Dunaliella tertiolecta, Chlamydomonas reinhardtii wild-type and cell wall-lacking mutant was studied in bubble columns. No cell damage was found for D. tertiolecta and C. reinhardtii (wild-type) up to superficial gas velocities of 0.076 and 0.085 m s-1, respectively, suggesting that high superficial gas velocities alone cannot be responsible for cell death and, consequently, bubble bursting cannot be the sole cause for cell injury. A death rate of 0.46 ± 0.08 h-1 was found for C. reinhardtii (cell wall-lacking mutant) at a superficial gas velocity of 0.076 m s-1, and increased to 1.01 ± 0.29 h-1 on increasing superficial gas velocity to 0.085 m s-1. Shear sensitivity is thus strain-dependent and to some extent the cell wall plays a role in the protection against hydrodynamic shear. When studying the effect of bubble formation at the sparger in batch cultures of D. tertiolecta by varying the number of nozzles, a death rate of 0.047 ± 0.016 h-1 was obtained at high gas entrance velocities. D. tertiolecta was cultivated in a pilot- plant reactor under different superficial gas velocities of up to 0.026 m s-1, with relatively low gas entrance velocities and no cell damage was observed. There is some indication that the main parameter causing cell death and damage was the gas entrance velocity at the sparger
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