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 mumol photons m(-2) s(-1). A modified standard F/2 medium with a twofold of silica and phosphorus concentrations was illustrated to result in a better growth of this diatom. Vitamin B-12 in the range from 1 to 3 mug L-1 did not significantly affect the growth. A maximum cell density obtained from this small glass bubble column was approximately 5.8 x 10(6) cells mL(-1) with a maximum specific growth rate of 3.80 x 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 x 10(-2) h(-1) with a maximum cell concentration of 8.88 x 10(6) 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 (g) achievable was 9.65 x 10(-2) h(-1) and the cell concentration during the harvest period was 4.08 x 10(6) Cells mL(-1). (C) 2004 Elsevier B.V. All rights reserved.