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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Carotenoid and fatty acid metabolism in nitrogen-starved Dunaliella salina, a unicellular green microalga
Lamers, P.P. ; Janssen, M. ; Vos, R.C.H. de; Bino, R.J. ; Wijffels, R.H. - \ 2012
Journal of Biotechnology 162 (2012)1. - ISSN 0168-1656 - p. 21 - 27.
beta-carotene - biochemical-composition - nutrient limitation - low-temperature - high light - accumulation - bardawil - alga - induction - stress
Nitrogen availability and light intensity affect ß-carotene overproduction in the green alga Dunaliella salina. Following a previous study on high-light stress, we here report on the effect of nitrogen depletion on the growth characteristics and ß-carotene as well as fatty acid metabolism of D. salina under a constant light regime in a turbidostat. Upon nitrogen depletion, the biomass yield on absorbed light approximately doubled, due to a transient increase in cell division rate, swelling of the cells and a linear increase of the density of the cells. Simultaneously, ß-carotene started to accumulate up to a final intracellular concentration of 14 mg LCV-1 (i.e. 2.7% of AFDW). This ß-carotene production accounted for 6% of the increased density of the cells, indicating that other biochemical constituents accumulated as well. Since D. salina accumulates ß-carotene in lipid globules, we also determined the fatty acid content and composition of D. salina. The intracellular concentration of the total fatty acid pool did not change significantly during nitrogen starvation, indicating that ß-carotene and total fatty acid accumulation were unrelated, similar to what was found previously for high-light treated cells. However, for both high-light and nitrogen stress, ß-carotene accumulation negatively correlated with the degree of unsaturation of the total fatty acid pool and, within the individual fatty acids, correlated positively with oleic acid biosynthesis, suggesting that oleic acid may be a key component of the lipid-globule-localized triacylglycerols and thereby in ß-carotene accumulation.
Carotenoid and Fatty Acid Metabolism in Light-Stressed Dunaliella salina
Lamers, P.P. ; Laak, C.W. ; Kaasenbrood, P.S. ; Lorier, J. ; Janssen, M.G.J. ; Vos, C.H. de; Bino, R.J. ; Wijffels, R.H. - \ 2010
Biotechnology and Bioengineering 106 (2010)4. - ISSN 0006-3592 - p. 638 - 648.
beta-carotene - halotolerant alga - low-temperature - bardawil - salina - accumulation - marine - chlorophyta - microalgae - biotechnology
Carotene is overproduced in the alga Dunaliella salina in response to high light intensities. We have studied the effects of a sudden light increase on carotenoid and fatty acid metabolism using a flat panel photobioreactor that was run in turbidostat mode to ensure a constant light regime throughout the experiments. Upon the shift to an increased light intensity, -carotene production commenced immediately. The first 4 h after induction were marked by constant intracellular levels of -carotene (2.2 g LCV-1), which resulted from identical increases in the production rates of cell volume and -carotene. Following this initial phase, -carotene productivity continued to increase while the cell volume productivity dropped. As a result, the intracellular -carotene concentration increased reaching a maximum of 17 g LCV-1 after 2 days of light stress. Approximately 1 day before that, the maximum -carotene productivity of 30 pg cell-1 day-1 (equivalent to 37 mg LRV-1 day-1) was obtained, which was about one order of magnitude larger than the average productivity reported for a commercial -carotene production facility, indicating a vast potential for improvement. Furthermore, by studying the light-induced changes in both -carotene and fatty acid metabolism, it appeared that carotenoid overproduction was associated with oil globule formation and a decrease in the degree of fatty acid unsaturation. Our results indicate that cellular -carotene accumulation in D. salina correlates with accumulation of specific fatty acid species (C16:0 and C18:1) rather than with total fatty acid content
The Selectivity of Milking of Dunaliella salina
Kleinegris, D.M.M. ; Janssen, M.G.J. ; Brandenburg, W.A. ; Wijffels, R.H. - \ 2010
Marine Biotechnology 12 (2010)1. - ISSN 1436-2228 - p. 14 - 23.
beta-carotene production - 2-phase bioreactors - low-temperature - photosystem-ii - green-algae - accumulation - bardawil - chlorophyll - extraction - protein
The process of the simultaneous production and extraction of carotenoids, milking, of Dunaliella salina was studied. We would like to know the selectivity of this process. Could all the carotenoids produced be extracted? And would it be possible to vary the profile of the produced carotenoids and, consequently, influence the type of carotenoids extracted? By using three different D. salina strains and three different stress conditions, we varied the profiles of the carotenoids produced. Between Dunaliella bardawil and D. salina 19/18, no remarkable differences were seen in the extraction profiles, although D. salina 19/18 seemed to be better extractable. D. salina 19/25 was not “milkable” at all. The milking process could only be called selective for secondary carotenoids in case gentle mixing was used. In aerated flat-panel photobioreactors, extraction was much better, but selectiveness decreased and also chlorophyll and primary carotenoids were extracted. This was possibly related to cell damage due to shear stress
Mechanism of extraction of Beta-Carotene from microalga Dunaliellea salina in two-phase bioreactors
Hejazi, M. ; Kleinegris, D.M.M. ; Wijffels, R.H. - \ 2004
Biotechnology and Bioengineering 88 (2004)5. - ISSN 0006-3592 - p. 593 - 600.
acid - bardawil - accumulation
We show that it is possible to extract beta-carotene selectively from Dunaliella salina in two-phase bioreactors. The cells continue to produce beta-carotene and the extracted part is substituted by newly produced molecules. This process is called "milking." We performed several experiments to understand the exact mechanism of the extraction process. The results show that direct contact between the cells and the biocompatible organic solvent was not a requirement for the extraction but it accelerated the extraction. Electron microscopy photographs showed an undulated shape of the cell membrane and a space between the cell and the chloroplast membranes in the cells growing in the presence of dodecane (a biocompatible solvent). Extra-chloroplast beta-carotene globules located in the space between the cell and the chloroplast membranes were observed in these cells as well. It was shown that dodecane was taken up by the cells. The concentration of dodecane in the cells was about 13 pg.cll(-1). It can be concluded that dodecane uptake by the cells is responsible for the morphological changes in the cells and leads to more activity in the cell membrane. The results suggest two possible modes of extraction. One of the mechanisms is transport of the globules from the chloroplast to the space between the cell and the chloroplast membranes and subsequently from there to the outside by exocytosis. Another possible mode for the extraction could be release of beta-carotene from the globules as a result of alterations in the membrane in response to the uptake of dodecane. beta-Carotene molecules diffuse from the chloroplast to the space between the cell and the chloroplast membranes and from there to the medium either by diffusion or by exocytosis after accumulation in the vesicles. (C) 2004 Wiley Periodicals, Inc.
Effect of light intensity on Beta-carotene production and extraction by Dunaliella salina in two-phase bioreactors
Hejazi, M. ; Wijffels, R.H. - \ 2003
Biomolecular Engineering 20 (2003)4-6. - ISSN 1389-0344 - p. 171 - 175.
irradiance - bardawil - growth
Application of two-phase bioreactors is a useful technique for improvement of the productivity of fermentations. Fermentative extraction of the products in situ is performed in this technique. The effect of light intensity on the extraction of ß-carotene from Dunaliella salina, in the fermentative extraction, has been investigated. Three different average light exposures were applied: 1.5×10-8 (low), 2.7×10-8 (intermediate) and 4.5×10-8 (high) µmol s-1 per cell. Results show that ß-carotene content of the cells increases by increasing the light exposure. Increase in the ß-carotene content of the cells is not necessarily coupled with an increase in the volumetric production of ß-carotene. Final volumetric production is about the same for the three bioreactors. ß-Carotene extraction rate is enhanced by the increase in the light exposure. The results suggest that extraction rate is related to ß-carotene content of the cells and is not essentially related to the volumetric production of ß-carotene. Although the effectiveness of extraction with respect to the light input is comparable for all light intensities applied, increasing the light input per cell leads to a higher volumetric extraction rate. Moreover, extracted ß-carotene stays very pure even so the extraction increased by the increase of light intensity.
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