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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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    Production efficiency of mussel bottom culture
    Capelle, Jacob J. - \ 2017
    Wageningen University. Promotor(en): Aad Smaal; P.M.J. Herman, co-promotor(en): Jeroen Wijsman. - Wageningen : Wageningen University - ISBN 9789463430869 - 240
    mussels - mussel culture - bottom culture - efficiency - population dynamics - culture techniques - biomass production - improvement - shellfish culture - aquaculture - mossels - mosselteelt - bodemcultuur - efficiëntie - populatiedynamica - kweektechnieken - biomassa productie - verbetering - schaal- en schelpdierenteelt - aquacultuur

    Mussel bottom culture is an extensive type of aquaculture; it depends on natural resources for feed, seed and space. It consists of the translocation of seed from natural beds to designed culture areas, where mussel farmers try to improve production efficiency. Production efficiency is measured by the relative biomass production (RBP) expressed as units of biomass harvested from one unit of biomass seeded, it increases with mussel growth and decreases with mussel mortality. Mussel bottom culture makes use of nature and also depends on nature. Cultured mussels are subject to similar environmental factors that influence growth and mortality on natural mussel beds, with additional effects of anthropogenic factors. In this thesis we focus on dynamics of mussel beds and the impact and effectivity of culture activities on mussel production yield. The major objectives are stated as: (1) to better understand the population dynamics of subtidal mussel populations, (2) to analyze what factors determine production efficiency in mussel bottom culture and how this can be improved. On natural mussel beds mussels organise in patterns that enhance food delivery and resilience of the bed. On culture plots mussels are seeded in concentric seeding patterns. Seeding techniques concentrate mussels locally within the culture plot area, resulting in high local mussel densities; this increases competition and limits the spatial re-organisation of mussels in the bed. Consequently, seeding on culture plots is followed by a large size and density dependent seeding loss that ranges from about 40% for seed from fishery to 69% for smaller SMC seed. This loss was the major factor in determining the maximum RBP. Losses in the grow-out stage were substantially lower, a subsequent density dependent loss was found for smaller mussels (<30 mm), and a non-density dependent loss for larger mussels (>30 mm). Shore crab predation is an important factor contributing to the higher losses at seeding. The effect of shore crab predation on mussel biomass production is higher than expected from previous studies. In an experiment on an intertidal culture plot in the Oosterschelde (NL), we observed that shore crab predation peaks directly after seeding and accounted for 33% of the total losses within five weeks after seeding. Spatial patterns in the survival rates of natural mussel beds in the Wadden Sea show better seed survival in areas with intermediate salinity (mean annual salinity 17.5-22.5 mg l-1). This suggests that mussel survival is negatively related to sea star distribution, which is largely controlled by salinity. Natural beds that escape predation are found at lower salinities and mussels on these beds showed low growth rates, also because of a lower food quality in these areas. Mussel culture strongly affects the population dynamics of the subtidal mussel population, through relaying of mussels from natural mussel beds to culture plots. Culture plots are located in more saline regions of the Wadden Sea (mean annual salinity 25.8 mg l-1), compared to natural mussel beds. This activity increased mussel growth and survival because food quality on culture plots is high and predation is prevented. As a result, average biomass production is higher on culture plots than on natural mussel beds and this difference increases over time. A more efficient seed use on the available area, that can be obtained by reducing seeding losses will increase RBP, maximum biomass production and increases maximum profit. Our results suggest that this can be achieved by seeding homogeneously in low densities.

    Tegengaan van kwaliteitsverlies door stress bij weefselkweek
    Krens, F.A. ; Klerk, G.J.M. de - \ 2013
    Wageningen : Plant Research International - 29
    vermeerderingsmateriaal - weefselkweek - kweektechnieken - stress - arabidopsis thaliana - in vitro kweek - hypoxie - oxidatieve stress - hyperhydriciteit - landbouwkundig onderzoek - gewaskwaliteit - propagation materials - tissue culture - culture techniques - stress - arabidopsis thaliana - in vitro culture - hypoxia - oxidative stress - hyperhydricity - agricultural research - crop quality
    Het onderzoek in dit project betrof stress bij planten gerelateerd aan aspecten van weefselkweek. Door de invloed van deze stress op kwaliteit en kwantiteit van de geproduceerde planten leiden in vitro vermeerderingsbedrijven grote verliezen. In deze publicatie verslag van onderzoek bij de zandraket, Arabidopsis thaliana, hét modelgewas bij uitstek in het moleculair genetische onderzoek bij planten. Daarnaast werden enkele commerciële gewassen bestudeerd.
    Zonder transport staat alles stil, ook in weefselkweek : oplossing ligt in bevordering verdamping
    Klerk, G.J.M. de; Kierkels, T. ; Heuvelink, E. - \ 2013
    Onder Glas 10 (2013)9. - p. 18 - 19.
    glastuinbouw - plantenvermeerdering - weefselkweek - kweektechnieken - in vitro kweek - transpiratie - tca - plantenontwikkeling - greenhouse horticulture - propagation - tissue culture - culture techniques - in vitro culture - transpiration - tca - plant development
    Nuchter beschouwd is het opmerkelijk dat planten in staat zijn in kweekbuizen te groeien. Het is daarom niet verwonderlijk dat zich regelmatig problemen voordoen. De oplossing daarvan is van groot belang voor de praktijk. Dat maakt snelle vermeerdering door weefselkweek voor veel meer gewassen toegankelijk.
    Roofwantsen tegen trips in chrysant: Orius majusculus en Orius niger
    Linden, A. van der; Staaij, M. van der - \ 2011
    Bleiswijk : Wageningen UR Glastuinbouw (Rapporten GTB 1147) - 23
    biologische bestrijding - chrysanthemum - orius - thrips - kweektechnieken - glastuinbouw - nederland - biological control - chrysanthemum - orius - thrips - culture techniques - greenhouse horticulture - netherlands
    Referaat Roofwantsen, Orius spp. kunnen behalve tripsnimfen ook volwassen trips eten. Omdat Orius niger volgens verschillende auteurs niet gevoelig zou zijn voor korte daglengte, waarbij sommige Orius soorten stoppen met eileg, werden deze roofwantsen buiten verzameld en in kweek genomen. Het kweken op peulen van sperzieboon of stengeldelen van bijvoet met eieren van Ephestia lukte onvoldoende. Het kweken lukte beter op planten waaronder Artemisia vulgaris en Amaranthus caudatus, maar toch onvoldoende voor een goedlopende kweek. In een kas met chrysant werd daarom tussen eind februari en begin april Orius majusculus losgelaten. Deze soort kon zich tot in oktober in opeenvolgende en overlappende plantingen van chrysant handhaven. Behalve trips werd ook bladluis gegeten. Het aantal trips op de planten bleef in de zomer lager dan 1 trips adult of nimf per tak. Er waren slechts onduidelijke symptomen van trips op de bladeren te zien. Waarschijnlijk was de behaalde dichtheid van 1 Orius nimf of adult per 5 takken het maximaal haalbare bij deze aantallen trips. In het najaar liep het aantal trips, zowel Frankliniella occidentalis als Echinothrips americanus, op. Orius majusculus bleek een groot deel van het jaar succesvol volwassen trips en trips nimfen te eten in chrysant. Abstract Minute pirate bugs, Orius spp., are able to prey on both nymphs and adults of thrips. Orius niger was collected outdoors in order to set up a rearing. This species would not be subject to reproductive diapause according to several authors. Rearing on bean pods or pieces of stem of Artemisia vulgaris with eggs of Ephestia was not very successful. Rearing on plants such as Artemisia vulgaris or Amaranthus caudatus succeeded better, but still insufficient. Instead of Orius niger, Orius majusculus was released in a greenhouse planted with chrysanthemum between the end of February and the beginning of April. This species reproduced in subsequent and overlapping plantings of chrysanthemum until October. They preyed both on thrips and apids. During summer the number of thrips was less than 1 adult or nymph per plant. The thrips symptoms on the leaves were indistinct. The number of 1 Orius nymph or adult per 5 plants was probably the maximal achievable number in relation with this number of thrips. In autumn the number of thrips, both Frankliniella occidentalis and Echinothrips americanus increased. Orius majusculus was successful in predating both adult thrips and nymphs during most of the year.
    Epigenetische effecten : onverwachte afwijkingen in weefselkeek : bossige planten, slechte bloei of overmatig callusvorming
    Smulders, M.J.M. ; Klerk, G.J.M. de; Heuvelink, E. - \ 2011
    Onder Glas 8 (2011)2. - p. 32 - 33.
    glastuinbouw - kweektechnieken - weefselkweek - plantenvermeerdering - afwijkingen, planten - epigenetica - vermeerderingsmateriaal - sierplanten - gewaskwaliteit - groenten - potplanten - greenhouse horticulture - culture techniques - tissue culture - propagation - plant disorders - epigenetics - propagation materials - ornamental plants - crop quality - vegetables - pot plants
    In-vitrovlees: yuck!(?) : een eerste verkenning van een eerste reactie
    Weele, C.N. van der - \ 2010
    Den Haag : LEI Wageningen UR (LEI-nota 10-179) - 23
    houding van consumenten - kunstvlees - in vitro kweek - kweektechnieken - productontwikkeling - consumentengedrag - consumer attitudes - meat analogues - in vitro culture - culture techniques - product development - consumer behaviour
    In de zoektocht naar nieuwe eiwitbronnen vormt in-vitrovlees één van de sporen. Het idee is om uit dierlijke stamcellen spierweefsel te laten groeien, ofwel vlees, met behulp van weefselkweektechnieken. Daarvoor zijn dierlijke cellijnen nodig, maar dieren komen er niet aan te pas. Daarnaast is de productie van in-vitrovlees potentieel efficiënter en duurzamer. Door deze mogelijke voordelen voor dieren en voor duurzaamheid bestaat er een grote maatschappelijke vraag om dit idee door nader onderzoek verder uit te werken. In biologisch opzicht zijn er nog veel obstakels te overwinnen. Vanuit maatschappelijk oogpunt springen enerzijds de voordelen in het oog, anderzijnds rijst de vraag of mensen in-vitrovlees ook echt zouden willen eten. Het komt nogal eens voor dat mensen met enige afschuw reageren op het idee van in-vitrovlees. Deze studie vormt een eerste verkenning van deze reactie, die in het Engels wordt aangeduid als 'yuck'-reactie.
    Bij weefselkweek is overgang van kweek naar kas een grote bottlenek: groei naar uitplanten aanzienlijk te verbeteren
    Klerk, G.J.M. de - \ 2009
    Onder Glas 6 (2009)6. - p. 44 - 45.
    tuinbouwbedrijven - waterbehoefte - weefselkweek - kweektechnieken - plantenveredeling - vermeerderingsmateriaal - beworteling - huidmondjes - ethyleen - glastuinbouw - market gardens - water requirements - tissue culture - culture techniques - plant breeding - propagation materials - rooting - stomata - ethylene - greenhouse horticulture
    Vanwege de zeer hoge luchtvochtigheid in weefselkweek functioneren de huidmondjes van weefselkweekplantjes nauwelijks, ook niet na het uitplanten. Om het verdampte water snel te kunnen aanvullen worden de plantjes vaak in weefselkweek beworteld en met wortel en al uitgeplant. Het uitplanten is verder te verbeteren door extra suiker of protectants tijdens de laatste weefselkweekfase te geven en door ophoping van het verouderingshormoon ethyleen tegen te gaan met ethyleenkillers zoals Power Pellets
    Productie en kostprijs van pootvis (WP 4)
    Schneider, O. ; Denekamp, J. - \ 2009
    Yerseke : IMARES (Rapport / Wageningen IMARES nr. C038/09) - 20
    visteelt - viskwekerijen - vermeerderingsmateriaal - kweektechnieken - aquacultuur - solea - kostenanalyse - prijsbepalende factoren - fish culture - fish farms - propagation materials - culture techniques - aquaculture - solea - cost analysis - price determining factors
    De cyclus van een marktwaardige consumptievis binnen de aquacultuur bestaat uit twee fases. De hatcheryfase, waar ouderdieren tot paaien worden gebracht en de nakomelingen tot pootvis worden gekweekt. En de doorgroeifase waar de pootvis wordt opgegroeid tot consumptievis. De prijs van deze consumptievis wordt mede bepaald door de kosten van de in eerste instantie ingekochte of voorgekweekte pootvis wat vaak een significant aandeel heeft in de kostprijsopbouw. De kostprijs van pootvis is opgebouwd uit verschillende soorten kosten. Alle factoren die van invloed zijn op de kweek van pootvis zijn in twee kostenposten te verdelen: lopende kosten en vaste kosten. Al deze kosten worden bepaald door biologische en technische invloeden vanuit het proces (mortaliteit, groeisnelheid, temperatuur etc.). Van een aantal vissoorten (zeebaars, Afrikaanse meerval) is de kostprijs en de kostprijsopbouw van pootvis bekend. Bij noorzee tong (Solea solea) is dit nog niet in kaart gebracht. Eerste pogingen gaan terug op berekeningen in de jaren 200 en 2001. Maar deze zijn niet publiek. Het is dus noodzakelijk om de kostprijs van tong pootvis te berekenen, om de haalbaarheid van tong kweek te onderbouwen.
    Ex situ cultivation of the soft coral Sinularia flexibilis for biotechnological exploration
    Khalesi, M.K. - \ 2008
    Wageningen University. Promotor(en): Rene Wijffels, co-promotor(en): Rik Beeftink. - [S.l.] : S.n. - ISBN 9789085049128 - 130
    koralen - teelt - kweektechnieken - biotechnologie - biologische productie - geneesmiddelen - aquacultuur - corals - cultivation - culture techniques - biotechnology - biological production - drugs - aquaculture
    Many of the marine sessile invertebrates such as soft corals produce toxins that help protect the coral from competitors and predators. These toxins are of medical importance (e.g. in cancer treatment). In recent years, there has been a focus to make use of marine organisms for this purpose. As a result, marine biotechnology is developing to meet the increasing demand. This thesis deals with one of the biomedically useful symbiotic soft corals, Sinularia flexibilis that co-exists with dinoflagellate algae or zooxanthellae, which together with the host (animal) form a holobiont. This species also produces compounds as intra-cellular photo-protective agents in shallow-water habitats; these compounds are called mycosporine-like amino acids (MAAs) with potential application in health care as sunscreens.
    An advantage of this coral is that from a parent colony of coral, a lot of clones may be obtained via asexual reproduction (fragmentation). If this procedure is used natural marine resources can be preserved because excessive sea harvest of the source coral is not necessary. Because there is an increasing demand for drugs such as antibiotics and anticancers of marine origin, the main goal of this research was to culture S. flexibilis at optimized captive conditions, so that they can supply, in part, the future demand for drug development. To have an overview of scientific research on the metabolites of this species, we reviewed studies into these secondary compounds and listed various alternatives for the captive cultivation of corals (Chapter 2). In this research, we studied the impact of environmental parameters such as irradiance (Chapter 3), the relevance of phototrophy and heterotrophy (Chapter 4), the effect of nutrient enrichment (Chapter 5) and of water velocity (Chapter 6) on the coral growth and physiology in captivity, and on the biosynthesis of secondary metabolites. As an alternative to the cultivation of whole organisms, the cultivation of coral cells is described in Chapter 7.

    - Secondary metabolites and cultivation opportunities (Chapter 2)
    To have an overview of scientific research on the secondary metabolites of this species, we reviewed studies into these compounds. Our review showed that a high percentage of these compounds are cytotoxic and may be promising as future anti-cancer drugs. To provide coral biomass, we discussed various approaches, including captive aquaculture.

    - Light-dependency (Chapter 3)
    As mentioned above, S. flexibilis is a symbiotic coral: it depends on the translocated photosynthates from its algal symbionts, the zooxanthellae. Accordingly, factors that promote photosynthesis of zooxanthellae should be given serious attention. Of these, light is being considered as the most important environmental factor affecting growth of symbiotic corals due to translocated photosynthates from zooxanthellae. Light intensity or photosynthetic photon flux density is important in promoting photosynthesis by zooxanthellae. Hence, finding optimum irradiance by applying various light intensities was the objective in the 3rd chapter of this thesis. Optimum specific growth rate (mu) of S. flexibilis was found at a range from 100 to 400 μmol quanta m⁻² s⁻¹. More or less constant mu over a range of light intensities was attributed to photoacclimation of the coral. The content of flexibilide, a major terpene of S. flexibilis, increased with light intensity; it showed lower contents at both very low and very high irradiances. The increase in flexibilide was explained as the coral’s response to stressful condition of high irradiances. The decrease in flexibilide content at the light extremes was ascribed to low photosynthesis due to weak and/or strong light intensities.

    - Phototrophy and heterotrophy (Chapter 4)
    The light-dependency of S. flexibilis and its zooxanthellae indicates that the algal photosynthates fuel metabolic requirements of the host coral. Our long-term findings verified this fact and showed that in the absence of light, even with addition of food , the coral was not able to grow nor to survive. Similarly, corals kept under optimal light without a continuous supply of ambient nutrient supply, were incapable to grow and survive. On the other hand, both colonies of S. flexibilis incubated at normal irradiances with or without extra feeding, grew well using available nutritional sources. In the same way, the coral physiology, i.e. the contents of zooxanthellae, chlorophyll, and MAAs reflected the effects of the above parameters. Therefore, both phototrophy and heterotrophy on ambient resources are important for S. flexibilis to perform optimally.
    In short-term, measurements of metabolic rate (photosynthesis and respiration) and estimating daily energy budget for S. flexibilis showed complete phototrophy. Estimating the daily ‘Contribution of Zooxanthellae to Animal Respiration (CZAR)’ yielded high values of zooxanthellae contribution to the host metabolism. Using energy equivalents for photosynthetically fixed carbon, we established that a small fraction of translocated fixed carbon is allocated to coral growth. Based on dependency of S. flexibilis on ambient nutritional sources in addition to irradiance, we concluded that photosynthates of zooxanthellae are deficient in growth-enhancing nutrients, especially nitrogenous compounds, which indeed need to be fulfilled heterotrophically for overall coral growth.

    - Nutrient enrichment and feeding (Chapter 5)
    To study the effect of essential nutrients enrichment (nitrogen and phosphorous) on the specific growth rate of S. flexibilis and its zooxanthellae, we performed prolonged experiments (Chapter 5). Our results showed that ammonium addition did not have any positive effect on coral growth; it reduced the growth of S. flexibilis at high levels. The coral was able to recover after high ammonium loadings. The effect of phosphate enrichment on the coral growth was neutral. Enrichment of this species with ammonium for three weeks resulted in an increase in both zooxanthellae and chlorophyll content after the 1st week of enrichment, followed by a decrease (equal to control) for the next two weeks. We concluded that zooxanthellae multiplication because of ammonium addition was temporary.

    - Flow-dependency (Chapter 6)
    The importance of water flow for sessile organisms such as S. flexibilis is to provide them with nutrition (e.g. suspended food particles), remove the coral’s wastes, and to facilitate exchange of substrates and products through modifying the boundary layer near their bodies. Long-term exposure of S. flexibilis to various water velocities resulted in the finding that the coral’s growth, physiology, and morphology are affected by flow regimes. Specific growth rates were optimal at an optimum water velocity of 11 cm s⁻¹. Based on the contents of zooxanthellae, chlorophyll, and total protein at the same water velocity for optimum growth, we concluded that optimal water velocity facilitated nutrient uptake through modification of the boundary layer thickness. This modification was aided by flexibility and swaying behaviour of S. flexibilis and also its polypary structure. High water velocities caused both coral and polyp retraction, which reduced exposure of its photosynthesizing surfaces together with decreased nutrient uptake resulting in low specific growth rates and also physiological parameters.

    - Coral cell culture (Chapter 7)
    We investigated cellular culture of S. flexibilis (Chapter 7) as an alternative to the coral supply, using different media and cell dissociation methodologies. A mechanical dissociation process provided the best method for the cell extraction procedure, maintaining always the highest number of cells extracted and subsequent cellular growth in all treatments. The best results from chemical reagents for dissociation was found using trypsin-EDTA. Coral cells obtained by spontaneous dissociation did not show signs of growth. Light was revealed as a fundamental parameter to be taken into account for the coral cell culture. The media GIM and GMIM displayed the best results for the maintenance of coral cell cultures. By means of a molecular test using Internal Transcribed Spacer (ITS) primers, the similarity of cultured coral cells and zooxanthellae at different culture media with those in the coral tissue was confirmed. In addition to possibility of the coral cell culture depending on both culture conditions and methodologies, our genetical cell identification test provided a reliable proof for the true cultured cells of S. flexibilis.
    Onderzoek naar mogelijkheden en beperkingen bovenafscherming (een kier van 5% heeft vergelijkbaar effect als 5% ingeweven kiertjes)
    Rijssel, E. van; Wageningen UR Glastuinbouw, - \ 2007
    Onder Glas 4 (2007)1. - p. 14 - 15.
    tuinbouw - kassen - bekleding, bouw - belichting - bedrijfsvoering - kweektechnieken - thermoregulatie - energie-uitwisseling - warmtebalans - schermen - glastuinbouw - horticulture - greenhouses - cladding - illumination - management - culture techniques - thermoregulation - energy exchange - heat balance - blinds - greenhouse horticulture
    Een overzicht van de resultaten van het onderzoek naar bovenafscherming in kassen. Op basis van dit onderzoek werden de regels om de uitstraling van assimilatielicht te beperken aangepast. Een reportage over de resultaten van bovenafscherming
    Verkenning van mogelijkheden voor mosselteelt op open zee & een mosselkansenkaart voor de Noordzee
    Steenbergen, J. ; Verdegem, M.C.J. ; Jol, J. ; Perdon, K.J. ; Kamermans, P. - \ 2005
    IJmuiden : RIVO (Rapport / Nederlands Instituut voor Visserij Onderzoek (RIVO) C088/05)
    mossels - mosselteelt - noordzee - innovaties - economische haalbaarheid - kweektechnieken - technologie - mussels - mussel culture - north sea - innovations - economic viability - culture techniques - technology
    Dit rapport geeft een overzicht van de huidige stand van zaken in de wereld omtrent mosselkweek op open zee. Daarnaast wordt, op basis van het voorkomen van mosselen, aangegeven welke locaties in het Nederlandse deel van de Noordzee potentieel geschikt kunnen zijn voor mosselkweek en/of mosselzaad invang. De ontwikkeling van mosselkweek op open zee vraagt een innovatieve stap. Hiervoor is andere expertise nodig dan die aanwezig is bij de huidige kweekpraktijk in Nederland. De ruwe omstandigheden op de Noordzee vereisen offshore technologie. Naast de technologische drempels die moeten worden overwonnen is het ook belangrijk dat wordt nagedacht hoe conflicten tussen verschillende gebruikers van de Noordzee (scheepvaart, zandwinning, visserij) voorkomen kunnen worden.
    Effect van weefselkweek-omstandigheden op de kwaliteit van weefselkweekmateriaal
    Klerk, G.J.M. de - \ 2004
    Lisse : PPO Bloembollen - 21
    weefselkweek - kweektechnieken - plantmateriaal - tuinbouw - tissue culture - culture techniques - planting stock - horticulture
    In dit project zijn procedures ontwikkeld om de groei van weefselkweekmateriaal na uitplanten te verbeteren. Hiertoe werden de condities tijdens de weefselkweekfase aangepast en werd onderzocht wat het effect was op de doorgroei na uitplanten. De verbeteringen waren vaak substantieel en de methodes eenvoudig toe te passen. Opsommend zijn de toepassingen (in volgorde wat betreft mogelijkheid tot snelle toepassing in de praktijk): - Het schadelijke effect van ethyleen en andere organische gassen die ophopen in de headspace van weefselkweekcontainers kan tegengegaan worden met Power Pellets. Hiervoor zijn zakjes speciaal voor toepassing in weefselkweek ontwikkeld. - Natuurlijk voorkomende beschermende stoffen (putrescine, proline, betaine) toegediend tijden weefselkweek kunnen negatieve effecten van stress bij acclimatisatie tegengaan. - Bij veel gewassen gaat acclimatiseren van in-vitro bewortelde planten beter. Een ander voordeel van in-vitro beworteling is de grotere flexibiliteit wat betreft het uitplantingstijdstip: als ex vitro wordt beworteld, moet de bewortelingsbehandeling kort na oogsten gegeven worden. - Extra nutriënten toegediend tijdens weefselkweek kunnen acclimatisatie bevorderen. - Weefselkweekplantjes hebben slecht-functionerende huidmondjes. Dit is waarschijnlijk het grootste mankement van weefselkweekplantjes. In de praktijk toegepaste oplossingen zijn na uitplanten de luchtvochtigheid langzaam omlaag brengen en uitplanten van bewortelde scheuten. In dit onderzoek zijn geen nieuwe mogelijkheden naar voren gekomen.
    Cultivation of Marine Sponges: From Sea to Cell
    Sipkema, D. - \ 2004
    Wageningen University. Promotor(en): Hans Tramper, co-promotor(en): Rene Wijffels; Ronald Osinga. - Wageningen : Detmer Sipkema - ISBN 9789085040743 - 184
    secundaire metabolieten - farmaceutische producten - sponsen - kweektechnieken - secondary metabolites - pharmaceutical products - sponges - culture techniques
    Marine sponges are one of the richest natural sources of secondary metabolites with a potential pharmaceutical application. A plethora of chemical compounds, with widely varying carbon skeletons, possessing among other anticancer, antiviral, antibiotic, antiinflammatory and antimalaria activity has been discovered. While for most metabolites their molecular mode of action is still unclear, for a substantial number of compounds the mechanisms by which they interfere with the pathogenesis of a wide range of diseases has been reported. Knowledge on the mode of action is one of the key factors required to transform bioactive compounds into medicines. The rich diversity in bioactive compounds from sponges has provided molecules that interfere with the pathogenesis of a disease at many different points, which increases the chance of developing selective drugs against specific targets (Chapter 2).Unfortunately, these secondary metabolites are usually present in trace amounts, and natural stocks are too small to sustain the development of widely available medicines. The development of ways to obtain large quantities of the secondary metabolites is therefore currently the most important quest. A number of biotechnological methods could potentially provide the required amount of bioactive substances. Three methods were studied in this thesis:

    Ex situculture

    The term ex situ culture refers to cultivation of functional sponges outside of the sea. One of the crucial issues for the ex situ cultivation of sponges is the design of a suitable growth medium. Generally sponges are regarded as particle feeders (bacteria and algae), but they are also capable of the uptake of (partly) dissolved organic carbon sources. The use of powdered substrates can be beneficial for the ex situ culture of sponges under controlled conditions, because an optimal mix of nutrients can be developed and a constant quality can be guaranteed. The ex situ growth rates of sponges cultured on these substrates could be improved, when compared to the sea, but they remain low and resulted in long-term experiments. In order to optimise the growth rate of sponges, it is important to have insight in the way that sponges grow. The suitability of three different models (linear, exponential and radial accretive growth) to describe the growth of both globose and encrusting sponges was assessed. For both morphological appearances, radial accretive growth was the preferred model to simulate the growth. The model can be a valuable tool to make a sound comparison between growth rates of different sponges. In addition, it can be used to study the quantitative effect of factors, such as pressure, light, current, age, temperature or the nutrient source or -concentration on the growth rate of sponges (Chapter 3).

    Primmorphs

    Primmorphs are spherical-shaped sponge-cell aggregates with a diameter of approximately 1 mm. They are formed from a dissociated cell suspension under gentle agitation and resemble buds and gemmules, which are the naturally produced asexual regeneration bodies. Primmorph formation seems to be a universal characteristic of marine sponges, as they were obtained from seven different species. By scanning electron microscopy (SEM) it was observed that the primmorphs are very densely packed sphere-shaped aggregates with a continuous pinacoderm (skin cell layer) covered by a smooth, cuticle-like structure. The latter characteristic is probably the reason why primmorphs are more robust than functional sponges and can be easily maintained for a long time. Incubation of primmorphs in a rich medium to attempt cultivation of the aggregates frequently resulted in the growth of bacterial, fungal and eukaryotic unicellular contaminants, which prevented a growth study of primmorphs. The addition of gentamycin or a mixture of penicillin and streptomycin could usually avoid bacterial contaminants, but eukaryotic contaminants were persistent. The addition of the fungicide amphotericin B or a cocktail of antibiotics (kanamycin, gentamycin, tylosin and tetracyclin) prevented the formation of primmorphs (Chapter 4).

    If primmorphs are actually a kind of experimentally induced regeneration bodies, they could develop into functional sponges. When primmorphs were maintained in seawater enriched with silicate (70 or 150 µM) it was observed that they indeed produced spicules (silica-based skeletal elements) and attached to the bottom of the culture dish, which never occurred at lower silicate concentrations (4 or 25 µM). These results may be explained by available knowledge on the molecular level. Silicate is known to induce the expression of silicatein, the enzyme involved in the production of spicules, at concentrations higher than 60 µM. In addition, silicate has been found to stimulate the biosynthesis of myotrophin, which enhances the production of collagen. Collagen is well known to play an important role in both the attachment of gemmules to a substratum and their subsequent morphogenesis (Chapter 5).

    Sponge-cell culture

    Sponge-cell culture may be the tool to overcome the low growth rate, and the corresponding low production rate of the bioactive metabolites of functional sponges. However, the presence of large numbers of associated bacteria, fungi and unicellular organisms inside sponges has been a major obstacle in the development of sponge-cell lines. They have prevented the formation of axenic sponge-cell suspensions, and proliferating sponge cells in cell cultures were therefore looked at with suspicion.

    For that reason two of prerequisites for the cultivation of sponge cells were developed:

    A method to distinguish sponge cells in culture from contaminants.A method to assess the viability of cells in culture.The 18S rRNA gene is a suitable marker to identify the origin of eukaryotic cells and a genetic detection method based on this gene was developed for the sponge Dysidea avara . The 18S rRNA gene from a Dysidea avara specimen was sequenced and compared to eukaryotic 18S rDNA sequence(s) that were picked up from a proliferating cell culture that originated from a dissociated Dysidea avara specimen. This method proved to be successful to unambiguously detect whether the cells in culture were actually sponge cells or contaminants (Chapter 6).

    Cell viability is an essential tool to study the effect of medium components on cell physiology. Especially in case of primary sponge-cell lines it is important to know whether slow growth is caused by a low specific growth rate or by a low viability of the cells. Trypan blue exclusion is a commonly used method to estimate the viability of cell cultures, but for unknown reasons this does not work properly with sponge cells. Therefore, a flow-cytometric viability assay, based on the combined use of fluorescein diacetate (FDA) and propidium iodide (PI) was developed. The effects of temperature, ammonium and the fungicide amphotericin B on the viability of a primary cell culture were studied as examples to assess the suitability of the test. Cell fluorescence measurements based on incubation of cells with FDA or PI, resulted in a good and reproducible estimate of the viability of primary sponge-cell cultures. It was found that the cells rapidly die at a temperature of 22 °C or higher, but that they are insensitive to ammonium concentrations up to 25 mM. Amphotericin B was found to be toxic to the cells (Chapter 7) and this could explain why no primmorphs were formed in the presence of this antibiotic.

    The current technical status of different methods to produce sponge metabolites was used to study the feasibility of pharmaceuticals from sponges at a large-scale. The production of the metabolites halichondrin B and avarol by chemical synthesis, wild harvest, mariculture, ex situ culture, primmorphs, sponge-cell culture, genetic modification and semi-synthesis were compared on a technical and economical basis, as far as possible. Halichondrin B from a Lissodendoryx sp. and avarol from Dysidea avara were used as model compounds as their products are opposites with respect to their natural concentration inside the sponge. It is concluded that for avarol, which is present in a relatively high concentration, mariculture and ex situ culture could offer feasible methods to compete with currently used medicines against psoriasis. For halichondrin B, the low concentration is a bottleneck for sponge biomass-based production of the compound. A combined approach of (genetically modified) bacterial fermentation (to produce a precursor molecule) followed by a limited number of chemical steps to produce molecules that are derived from sponge chemicals will probably be the most successful method to develop medicines from sponge metabolites that are present in low concentrations (Chapter 8).
    Kweekopzet van de Brachionus plicatilis op basis van kunstmatige voeders: Algenconcentraten en Rotimac als fast-food voor voedseldiertjes
    Vin, C.M. de - \ 2003
    IJmuiden : RIVO (Intern RIVO rapport 03.018) - 35
    kabeljauw - visteelt - zoöplankton - visvoeding - algenteelt - gekweekte producten - kweektechnieken - cod - fish culture - zooplankton - fish feeding - algae culture - cultured products - culture techniques
    De aquacultuursector is de snelst groeiende voedselproducerende sector ter wereld. De grootste producent is China, gevolgd door India en Japan. Binnen de Europese Unie is Spanje koploper, gevolgd door Frankrijk en Italië. Nederland komt op de vijfde plaats. Nederland heeft een aquacultuur productie van ongeveer 100.000 ton. Hiervan is 10.000 ton afkomstig uit de visteelt, de andere 90.000 ton is afkomstig uit de schelpdiersector. De meest geproduceerde vissoorten in Nederland zijn paling en meerval. Dit bestand wordt de laatste jaren uitgebreid met soorten als snoekbaars, tarbot en tong. Door de afname van de vangst van kabeljauw maar door de blijvende vraag voor deze vis, heeft het RIVO besloten voorbereidend onderzoek uit te voeren naar de mogelijkheid van het kweken van kabeljauw. Een cruciale voorwaarde voor het opkweken van kabeljauw is echter dat de kabeljauwlarven met rotiferen (kleine zoö-planktonische organismen) gevoerd moeten worden. Rotiferen moeten ter plaatse worden gekweekt. Hiervoor moest er op het RIVO een kweekinstallatie worden gerealiseerd, waarin rotiferen konden worden gekweekt, met minimale inspanning. Tevens werd gekeken naar de mogelijkheid om de rotiferen met instant voedsel (algenconcentraten en Rotimac) te voeren zodat er geen levende algen gekweekt moesten worden.
    Residuen van fungiciden in tarwestro in relatie tot de teelt van champignons: Dl. 2
    Bruchem, G.D. van; Traag, W.A. ; Verhagen, F.J.M. - \ 2001
    Wageningen : RIKILT (Rapport RIKILT 2001.001) - 11
    paddestoelen - kweektechnieken - tarwestro - fungicidenresiduen - analytische methoden - analytische scheikunde - mushrooms - culture techniques - wheat straw - fungicide residues - analytical methods - analytical chemistry
    Rooting of Juniperus and Chamæecyparis cuttings during summer and autumn
    Lenartowicz, A. - \ 1983
    Boskoop : Proefstation voor de Boomkwekerij - 23
    juniperus - chamaecyparis - houtachtige planten als sierplanten - kweektechnieken - juniperus - chamaecyparis - ornamental woody plants - culture techniques
    Rooting of various types of softwood cuttings of Acer palmatum
    Lenartowicz, A. - \ 1980
    Boskoop : Proefstation voor de Boomkwekerij - 8
    acer palmatum - houtachtige planten als sierplanten - kweektechnieken - acer palmatum - ornamental woody plants - culture techniques
    Het verband tussen hydraulica en hydrologie in de cultuurtechniek
    Kraijenhoff van de Leur, D.A. - \ 1958
    Wageningen : Veenman - 16
    hydraulica - hydrologie - kweektechnieken - openbare redes - hydraulics - hydrology - culture techniques - public speeches
    Met een uiteenzetting over de ontwikkelingenen in de cultuurtechniek, hydrologie en agrohydrologie, om vervolgens hoofdlijnen voor de hydraulica te bespreken. Ook de hoge zandgronden passeren de revue.
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