Effect of biomass concentration on secondary carotenoids and triacylglycerol (TAG) accumulation in nitrogen-depleted Chlorella zofingiensis
Mulders, K.J.M. ; Janssen, J.H. ; Martens, D.E. ; Wijffels, R.H. ; Lamers, P.P. - \ 2014
Algal Research 6 (2014)Part A. - ISSN 2211-9264 - p. 8 - 16.
fatty-acid-metabolism - haematococcus-pluvialis - dunaliella-salina - environmental-stresses - lipid-accumulation - green microalga - high light - chlorophyceae - astaxanthin - starvation
The effect of biomass-specific photon absorption rate on triacylglycerol (TAG) and secondary carotenoid yield was studied. Chlorella zofingiensis (Chlorophyta) was cultivated batch-wise with sufficient initial nitrogen to produce 2.5, 3.4 and 4.1 g L-1 prior to nitrogen depletion, which resulted in biomass-specific photon absorption rates of 4.7, 3.5 and 2.9 µmolph g dry weight-1 s-1, respectively. During nitrogen starvation, the TAG as well as secondary carotenoid yield on light did not differ between the cultures, which indicates that in the studied range the biomass-specific photon absorption rate did not affect the amounts of energy used for TAG and secondary carotenoid production. The maximal TAG yield on light (320 mg molph -1) was higher than values reported before for microalgae. Besides, for the first time the secondary carotenoid yield on light was reported (maximally 2.75 mg molph -1).
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.