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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    Long-chain vitamin K2 production in Lactococcus lactis is influenced by temperature, carbon source, aeration and mode of energy metabolism
    Liu, Yue ; Bennekom, Eric O. Van; Zhang, Yu ; Abee, Tjakko ; Smid, Eddy J. - \ 2019
    Microbial Cell Factories 18 (2019)1. - ISSN 1475-2859
    Aeration - Carbon source - Long-chain MKs - Menaquinone - Natural enrichment - Respiration - Vitamin K2

    Background: Vitamin K2 (menaquinone, MK-n) is a lipid-soluble vitamin that functions as a carboxylase co-factor for maturation of proteins involved in many vital physiological processes in humans. Notably, long-chain vitamin K2 is produced by bacteria, including some species and strains belonging to the group of lactic acid bacteria (LAB) that play important roles in food fermentation processes. This study was performed to gain insights into the natural long-chain vitamin K2 production capacity of LAB and the factors influencing vitamin K2 production during cultivation, providing a basis for biotechnological production of vitamin K2 and in situ fortification of this vitamin in food products. Results: We observed that six selected Lactococcus lactis strains produced MK-5 to MK-10, with MK-8 and MK-9 as the major MK variant. Significant diversities between strains were observed in terms of specific concentrations and titres of vitamin K2. L. lactis ssp. cremoris MG1363 was selected for more detailed studies of the impact of selected carbon sources tested under different growth conditions [i.e. static fermentation (oxygen absent, heme absent); aerobic fermentation (oxygen present, heme absent) and aerobic respiration (oxygen present, heme present)] on vitamin K2 production in M17 media. Aerobic fermentation with fructose as a carbon source resulted in the highest specific concentration of vitamin K2: 3.7-fold increase compared to static fermentation with glucose, whereas aerobic respiration with trehalose resulted in the highest titre: 5.2-fold increase compared to static fermentation with glucose. When the same strain was applied to quark fermentation, we consistently observed that altered carbon source (fructose) and aerobic cultivation of the pre-culture resulted in efficient vitamin K2 fortification in the quark product. Conclusions: With this study we demonstrate that certain LAB strains can be employed for efficient production of long-chain vitamin K2. Strain selection and optimisation of growth conditions offer a viable strategy towards natural vitamin K2 enrichment of fermented foods, and to improved biotechnological vitamin K2 production processes.

    Light regulation of vitamin C in tomato fruit is mediated through photosynthesis
    Ntagkas, Nikolaos ; Woltering, Ernst ; Nicole, Celine ; Labrie, Caroline ; Marcelis, Leo F.M. - \ 2019
    Environmental and Experimental Botany 158 (2019). - ISSN 0098-8472 - p. 180 - 188.
    Ascorbic acid - Irradiance - Photosynthesis - Respiration - Spectrum - Vitamin C

    Higher levels of irradiance result in higher accumulation of ascorbate in leaves and fruits. Photosynthesis and respiration are an integral part of the physiological mechanism of light regulation of ascorbate in leaves, but little is known about the light regulation of ascorbate in fruit. The aim of this study was to investigate whether fruit illumination alone is sufficient for ascorbate increase in tomato fruit and whether this light signal is mediated by respiration and photosynthesis. First the changes of ascorbate with the progress of fruit development were investigated and subsequently detached fruit of different tomato genotypes were exposed to different irradiances and spectra. Measurements were performed on ascorbate, respiration, photosynthesis and chlorophyll content of the fruit. When attached to the plant, there was no effect of development on ascorbate from the mature green to the red stage. Detached fruit stored in darkness did not accumulate ascorbate. However, when exposed to 300–600 μmol m−2 s-1 light detached mature green fruit (photosynthetically active) substantially accumulated ascorbate, while mature red fruit (non-photosynthetically active) did not respond to light. Photosynthesis correlated with this increase of ascorbate while no correlation between respiration and ascorbate was found. Spectral effects on ascorbate in detached tomato fruit were limited. These results indicate that the signal for light regulation of ascorbate is perceived locally in the fruit and that fruit illumination alone is sufficient for a considerable increase in ascorbate levels for as long as the fruit contains chlorophyll. It is shown that photosynthetic activity of the fruit is an integral part of the response of ascorbate to light in tomato fruit. The light induced increase in ascorbate levels occurred in a range of genotypes, indicating a universal effect of light to ascorbate in tomato fruit.

    Dissolved oxygen dynamics in drainage ditches along a eutrophication gradient
    Lee, Gea H. van der; Verdonschot, Ralf C.M. ; Kraak, Michiel H.S. ; Verdonschot, Piet F.M. - \ 2018
    Limnologica 72 (2018). - ISSN 0075-9511 - p. 28 - 31.
    Dissolved oxygen saturation - Ecosystem functioning - Monitoring - Primary production - Respiration - Water quality

    The impact of eutrophication on the functioning of drainage ditch ecosystems is understudied. Therefore, we performed a field study to quantify the dissolved oxygen dynamics of ditches at different depths and seasons along a eutrophication gradient. During summer, a clear distinction in daily variation in dissolved oxygen saturation of the top water layer was observed between the trophic states. We recommend including dissolved oxygen dynamics as a functional parameter in drainage ditch monitoring programmes.

    Interactive effects of oxygen, carbon dioxide and flow on photosynthesis and respiration in the scleractinian coral Galaxea fascicularis
    Osinga, Ronald ; Derksen-Hooijberg, Marlous ; Wijgerde, Tim ; Verreth, Johan A.J. - \ 2017
    Journal of Experimental Biology 220 (2017)12. - ISSN 0022-0949 - p. 2236 - 2242.
    Carbon dioxide - Coral - Flow - Oxygen - Photosynthesis - Respiration

    Rates of dark respiration and net photosynthesis were measured for six replicate clonal fragments of the stony coral Galaxea fascicularis (Linnaeus 1767), which were incubated under 12 different combinations of dissolved oxygen (20%, 100% and 150% saturation), dissolved carbon dioxide (9.5 and 19.1 μmol l-1) and water flow (1-1.6 versus 4-13 cm s-1) in a repeated measures design. Dark respiration was enhanced by increased flow and increased oxygen saturation in an interactive way, which relates to improved oxygen influx into the coral tissue. Oxygen saturation did not influence net photosynthesis: neither hypoxia nor hyperoxia affected net photosynthesis, irrespective of flow and pH, which suggests that hyperoxia does not induce high rates of photorespiration in this coral. Flow and pH had a synergistic effect on net photosynthesis: at high flow, a decrease in pH stimulated net photosynthesis by 14%. These results indicate that for this individual of G. fascicularis, increased uptake of carbon dioxide rather than increased efflux of oxygen explains the beneficial effect of water flow on photosynthesis. Rates of net photosynthesis measured in this study are among the highest ever recorded for scleractinian corals and confirm a strong scope for growth.

    Microalgal biofilm growth under day-night cycles
    Blanken, Ward ; Martins Pito de Magalhaes, Ana ; Sebestyén, Petra ; Rinzema, Arjen ; Wijffels, René H. ; Janssen, Marcel - \ 2017
    Algal Research 21 (2017). - ISSN 2211-9264 - p. 16 - 26.
    Carbon-partitioning - Day-night cycles - Microalgal biofilms - Modelling growth - Respiration

    Microalgal biofilms of Chlorella sorokiniana were cultivated under simulated day-night cycles at high productivity and high photosynthetic efficiency. Comparing day-night to continuous illumination did not demonstrate differences in the light utilization efficiency. This indicates that biomass consumed overnight represents sugar consumption for synthesis of new functional biomass and maintenance related respiration. Modelling microalgal biofilm growth was employed to calculate maximum productivities and photosynthetic efficiencies. A light limited microalgal biofilm growth model in which both diurnal carbon-partitioning and maintenance under prolonged dark conditions were taken into account was developed, calibrated, and validated experimentally. Extended periods of darkness resulted in reduced maintenance related respiration. Based on simulations with the validated biofilm growth model, it could be determined that the photosynthetic efficiency of biofilm growth can be higher than that of suspension growth. This is related to the fact that the maintenance rate in the dark zones of the biofilm is lower compared to that in the dark zones of suspension cultures which are continuously mixed with the photic zone.

    Genotypic differences in metabolomic changes during storage induced-degreening of chrysanthemum disk florets
    Geest, Geert van; Choi, Young Hae ; Arens, Paul ; Post, Aike ; Liu, Ying ; Meeteren, Uulke van - \ 2016
    Postharvest Biology and Technology 115 (2016). - ISSN 0925-5214 - p. 48 - 59.
    Carbohydrate starvation - Chrysanthemum - Metabolomics - Respiration - Senescence - Storage

    Selecting chrysanthemum cultivars with long storability and vase life is a major challenge for breeders. The rate of degreening of disk florets during the postharvest phase is an important determinant of vase life. There is large genotypic variation in susceptibility to disk floret degreening. Our aim was to understand these genotypic differences at the physiological level. Carbohydrate starvation seemed to play a role, since application of sugars prevented degreening and degreening only occurred if florets had a long-term low carbohydrate content. In order to find out which metabolic processes could explain genotypic differences, we used 1H Nuclear Magnetic Resonance (NMR) spectroscopy profiling, High Performance Anion Exchange Chromatography (HPAEC) and respiration measurements to compare metabolic responses of three genotypes to carbohydrate starvation. HPAEC and NMR measurements showed that carbohydrate content could not fully explain genotypic differences. A genotype with intermediate sensitivity to degreening showed similar carbohydrate content compared to an insensitive one. However, respiration rate declined faster under carbohydrate starvation in a sensitive and intermediate sensitive genotype compared to an insensitive genotype, suggesting a more abrupt constraint on the mitochondrial electron transport chain and with that oxidative stress. Changes in the metabolic profile under carbohydrate starvation were diverse and revealed candidate processes associated with disk floret degreening. Camphor content increased and correlated positively with degreening insensitivity. Phenylpropanoids and flavonoids also increased upon carbohydrate starvation and the response was genotype specific. We propose the upregulation of the phenylpropanoid metabolism as important source of nitrogen in the form of harmful ammonia during carbohydrate starvation. Our results provide a framework to identify processes associated with genotypic differences in the response to carbohydrate starvation and susceptibility to floret degreening.

    Physiological markers for lily bulb maturity
    Gude, H. ; Verbruggen, J.J.M. ; Franssen, J.M. ; Schouten, E.T.J. ; Aanholt, J.T.M. Van; Boonekamp, P.M. - \ 2000
    In: XXV International Horticultural Congress, Part 7 / Herregods, M., International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789066058132 - p. 343 - 350.
    Abscisic acid - Bulbs - Dormancy - Lily - Maturity - Osmotic potential - Respiration - Sucrose

    The aim of this study was to find physiological markers for lily bulb maturity. This would provide a tool for the grower to determine the optimal time for lifting. The following physiological parameters were measured in daughter sprouts at two week intervals from week number 34 to 52: the abscisic acid (ABA) content, sucrose content, osmotic potential and respiratory activity. As experimental objects the cultivars Connecticut King (Asiatic hybrids; dormant at lifting), 'Star Gazer' (Oriental hybrids; dormant at lifting) and Snow Queen (longiflorums; non-dormant) were used. In each cultivar one or more parameters were found that changed considerably towards the moment of lifting. The most dramatic changes were observed in the parameters ABA- content, sucrose-content and osmotic potential in the cultivar Connecticut King'. The same trend was observed in Star Gazer', but to smaller extent. These results enable us to assess correlations of these parameters with the flower quality of the bulbs that were lifted at the same moments and stored below 0°C for flower production in the autumn of 1998. In 'Snow Queen only the sucrose content showed an increase with sprout development. Respiratory activity decreased towards the time of lifting in all cultivars. A correlation was found between the process of dormancy and the ABA content. Only in the dormant cultivars ('Connecticut King' and 'Star Gazer') the ABA content increased with sprout development and the increase in ABA level preceded the cessation in sprout growth.

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