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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
Source: PubMed

ABSTRACT 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.

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    • "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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