Effect of biomass concentration on secondary carotenoids and triacylglycerol (TAG) accumulation in nitrogen-depleted Chlorella zofingiensis

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)