Effect of light intensity on β-carotene production and extraction by Dunaliella salina in two-phase bioreactors
Food and Bioprocess Engineering Group, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands. Biomolecular Engineering
(Impact Factor: 3.17).
08/2003; 20(4-6):171-5. DOI: 10.1016/S1389-0344(03)00046-7
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 beta-carotene from Dunaliella salina, in the fermentative extraction, has been investigated. Three different average light exposures were applied: 1.5 x 10(-8) (low), 2.7 x 10(-8) (intermediate) and 4.5 x 10(-8) (high) micromol s(-1) per cell. Results show that beta-carotene content of the cells increases by increasing the light exposure. Increase in the beta-carotene content of the cells is not necessarily coupled with an increase in the volumetric production of beta-carotene. Final volumetric production is about the same for the three bioreactors. beta-Carotene extraction rate is enhanced by the increase in the light exposure. The results suggest that extraction rate is related to beta-carotene content of the cells and is not essentially related to the volumetric production of beta-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 beta-carotene stays very pure even so the extraction increased by the increase of light intensity.
Available from: Kavitha M.D.
- "Carotenoid biosynthesis is governed by the level and activity of carotenoid biosynthesis enzymes. Dunaliella when exposed to stress conditions such as salinity (Fazeli et al. 2006), high light (Hejazi and Wijffels 2003), or nutrient limitation (Raja et al. 2007), two stereoisomers of βcarotene , all-trans and 9-cis may be accumulated reaching up to 10% of the dry cell weight (Ben-amotz et al. 1982). Metabolic inhibitors like glyphosate (amino acid biosynthesis inhibitor), glufosinate ammonium which is also called as basta (glutamine synthase inhibitor in nitrogen metabolism pathway), DCMU (photosynthetic inhibitor), DPA (inhibitor of β-carotene C-4 oxygenase), nicotine (lycopene cyclase inhibitor) and caffeine (cytokinesis inhibitor) were evaluated to study their effect on growth, carotenoid profile and fatty acid profile of the marine micro alga D. bardawil under two different light intensities. "
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ABSTRACT: Dunaliella bardawil, a green alga accumulates high amount of β-carotene under stress conditions. This organism has been exploited for β-carotene at industrial scale. In the present work, various metabolic inhibitors like diphenylamine (DPA), nicotine, basta, glyphosate, DCMU [3-(3',4'-dichlophenyl)-1,1-dimethylurea] and caffeine were used in autotrophic medium, to understand their influence on carotenoid biosynthesis. The results indicated that these metabolic inhibitors influenced the production of carotenoids like wise, DPA and basta increased the contents of β-carotene (1.7 fold), glyphosate and DCMU for lutein (2.4 and 2 fold) caffeine for biomass yields (1.1 fold), while nicotine decreased the biomass yield (3.6 fold), β-carotene (2 fold) and lutein (10.5 fold).
Journal of Food Science and Technology -Mysore- 12/2013; 50(6):1130-6. DOI:10.1007/s13197-011-0429-6
Available from: umn.edu
- "Dunaliella has been found to be one of the richest natural sources of b-carotene (Hejazi and Wijffels, 2003; Raja et al., 2007; Zhu and Jiang, 2008). Under suitable conditions, Dunaliella can accumulate up to 10% of the dry cell weight of b-carotene (Loeblich, 1974; Jin and Melis, 2003). "
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ABSTRACT: The objective of this work was to quantify the kinetic behavior of Dunaliella primolecta (D. primolecta) subjected to controlled fluid flow under laboratory conditions. In situ velocities of D. primolecta were quantified by micron-resolution particle image velocimetry and particle tracking velocimetry. Experiments were performed under a range of velocity gradients and corresponding energy dissipation levels at microscopic scales similar to the energy dissipation levels of natural aquatic ecosystems. An average swimming velocity of D. primolecta in a stagnant fluid was 41 microm/s without a preferential flow direction. In a moving fluid, the sample population velocities of D. primolecta follow a log-normal distribution. The variability of sample population velocities was maximal at the highest fluid flow velocity in the channel. Local fluid velocity gradients inhibited the accrual of D. primolecta by twofold 5 days after the initiation of the experiment in comparison to the non-moving fluid control experiment.
Biotechnology and Bioengineering 09/2010; 107(1):65-75. DOI:10.1002/bit.22774
- "Understanding this mechanism would be important in optimization of the process and its extension for production of other high-value compounds from microalgae. Our previous results showed that the extraction rate was affected at least by two parameters: mixing rate of the aqueous and organic phases in the bioreactor (Hejazi et al., 2003a) and h-carotene content of the cells (Hejazi et al., 2003b). These results suggested that interaction between the solvent and the cell membrane as well as h-carotene function and location inside the cells could play an important role in the extraction. "
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ABSTRACT: 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.
Biotechnology and Bioengineering 12/2004; 88(5):593-600. DOI:10.1002/bit.20238
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