Physiology and xanthophyll cycle activity of Nannochloropsis gaditana.
The physiology of the violaxanthin-producing microalga Nannochloropsis gaditana is examined and the effect of environmental factors on the growth and cellular pigment content investigated in batch and continuous cultures. N. gaditana is slow-growing, with a maximum specific growth rate of 0.56 day(-1) at 23 degrees C. The xanthophyll cycle is present in this strain, but has a much lower activity than in higher plants and other species of Nannochloropsis. At 30 degrees C, under high light (1500 micromol photons m(-2) s(-1)), 33% of the violaxanthin pool was deepoxidated to antheraxanthin (76%) and zeaxanthin (24%) over 60 min. Addition of iodoacetamide dramatically affected the xanthophyll cycle activity: 50% of the violaxanthin was replaced by zeaxanthin (90%) within 30 min. This was attributed to an increase in membrane fluidity following iodoacetamide addition, resulting in a larger pool of violaxanthin available for conversion. Batch culture studies showed that a decrease in irradiance (from 880 to 70 micromol photons m(-2) s(-1)) can increase chlorophyll a and violaxanthin content by as much as 80% and 60%, respectively. Continuous cultures indicated that violaxanthin is a growth-rate-dependent product, but the violaxanthin content is less affected by dilution rate (in the range 0.12 to 0.72 day(-1)) and pH (6.8 to 7.8) than chlorophyll a. The optimum conditions for growth and violaxanthin production in continuous culture were found to occur at a dilution rate of 0.48 day(-1), a temperature of between 24 degrees C and 26 degrees C, and pH in the range 7.1 to 7.3.
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Department of Chemical Engineering, University of California at Berkeley, Berkeley, California 94720-1462, USA.
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D019149:Bioreactors; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D056890:Eukaryota / Q000254:growth & development / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007460:Iodoacetamide / Q000494:pharmacology; D008029:Lighting; D014975:Lutein / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology; D013696:Temperature; D024341:Xanthophylls / Q000378:metabolism; D065146:Zeaxanthins; D019207:beta Carotene / Q000031:analogs & derivatives* / Q000378:metabolism
D004791:Enzyme Inhibitors; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; C031140:antheraxanthin; C005613:violaxanthin; D014975:Lutein; D007460:Iodoacetamide