Cultivation of a diatom chaetoceros calcitrans in airlift bioreactor

Abstract

Optimal conditions for the growth of a diatom Chaetoceros calcitrans were investigated in the small glass bubble column of 2.5 L. The light intensity for the highest growth rate was found to be at 200 micromol photon m-2s-1. At this light intensity, the diatom required no dark period for it growth. A suitable nutrient for the growth of this diatom was found to be a modified standard F/2 medium with a two fold of silica and phosphorus concentrations. The cultivation of C.calcitrans in the ALBR was superior to that in the BC. This was due primarily to the well defined flow pattern in the ALBR which led to a more effective light utilization of the algae. The optimal aeration rate of 3 cm s-1 was found to yield a maximum specific growth rate of 0.074 h-1 with a cell concentration of 20.15x10x10x10x10x10x10 cells mL-1 in batch culture. A semi-continuous culture could be achieved where the harvest was performed at every 12 hours and with a harvesting volumeof 60% of the total culture volume. In this case, the maximum specific growth rate (micro) achievable in this semi-continuous culture was 0.0854 h-1 and the productivity of C.calcitrans was 4.138x10x10x10x10x10x10x10x10x10x10x10 cells d-1 (11.84 mg L-1d-1)