Conversion of NaHCO 3 to Na 2 CO 3 with a growth of Arthrospira platensis cells in 660 m 2 raceway ponds with a CO 2 bicarbonation absorber.

The weight ratio of Na ₂ CO ₃ /NaHCO ₃ was investigated in order to improve microalgal productivity in large-scale industrial operations by converting NaHCO ₃ to Na ₂ CO ₃ with a growth of Arthrospira platensis cells in 660 m ² raceway ponds. Two microalgal cultivation systems with a NaHCO ₃ by-product (SPBP) and a CO ₂ bicarbonation absorber (CBAP) were firstly thoroughly introduced. There was a 13.3% decrease in the initial weight ratio of Na ₂ CO ₃ /NaHCO ₃ resulting in a 25.3% increase in the biomass growth rate with CBAP, compared to that of SPBP. Increased sunlight intensity, solution temperature and pH all resulted in both a higher HCO 3 - absorbance and CO 3 2 - release, thereby increasing the weight ratio of Na ₂ CO ₃ /NaHCO ₃ during the growth of A. platensis. The biomass growth rate was peaked at 39.9 g m ^-2  day ^-1 when the weight ratio of Na ₂ CO ₃ /NaHCO ₃ was 3.7. Correspondingly, the cell pigments (chlorophyll a and carotenoid) and trichome size (helix pitch and trichome length) reached to a maximum state of 8.47 mg l ^-1 , 762 μg l ^-1 , 57 and 613 μm under the CBAP system.
(© 2019 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.)