Optimal growth conditions and the cultivation of Chaetoceros calcitrans in airlift photobioreactor

The optimal conditions for the growth of a diatom Chaetoceros calcitrans were investigated in a 2.5 L glass bubble column. The light intensity for the highest growth rate was shown to be at around 400 μmol photons m−2 s−1. A modified standard F/2 medium with a two-fold of silica and phosphorus concentrations was illustrated to result in a better growth of this diatom. Vitamin B12 in the range from 1 to 3 μg L−1 did not significantly affect the growth. A maximum cell density obtained from this small glass bubble column was approximately 5.8 × 106 cells mL−1 with a maximum specific growth rate of 3.80 × 10−2 h−1. The cultivation of C.calcitrans in the 17 L airlift photobioreactor (ALPBR) was illustrated to be superior to that in the bubble column with the same size. The operation with superficial gas velocity of 3 cm s−1 was found to give a maximum specific growth rate of 7.41 × 10−2 h−1 with a maximum cell concentration of 8.88 × 106 cells mL−1 in a batch culture. A semi-continuous culture could be achieved where the harvest was performed at every 12 h. In this case, the maximum specific growth rate (μ) achievable was 9.65 × 10−2 h−1 and the cell concentration during the harvest period was 4.08 × 106 cells mL−1.