Astaxanthin induction in Microalga H. pluvialis with flat panel airlift photobioreactors under indoor and outdoor conditions.

Astaxanthin was induced from Haematococcus pluvialis (NIES-144) under indoor and outdoor conditions using 17-, 50-, and 90-L flat-panel airlift photobioreactors (FP-APBRs). Preliminary experiments in 1.5-L bubble column photobioreactors (BC-PBRs) revealed that sterilized clean water with 3% CO2 aeration (1.47 cm(3) s(-1) CO2 loading) could best encourage astaxanthin accumulation at 18.21 g m(-3) (3.63% by weight). Operating 17-L FP-APBRs with these bubble column parameters under indoor conditions could further enhance astaxanthin to 26.63 g m(-3) (5.34% by weight). This was potentially due to the inherited up-lift force from the reactor that helped avoid cell precipitation by allowing the cells to be circulated within the reactor. In addition, the various sizes of FP-APBRs exhibited similar performance, implying a potential scale-up opportunity. However, similar operation under outdoor condition exhibited slightly poorer performance due to the light inhibition effect. The best outdoor performance was obtained with the FP-APBR covered with one layer of shading net, where 20.11 g m(-3) (4.47% by weight) of astaxanthin was resulted.