Effect of superficial gas velocity on growth of the green microalga Haematococcus pluvialis in airlift photobioreactor

Abstract

The green microalga Haematococcus pluvialis NIES144 was cultured in a 3 L airlift photobioreactor at 27±1°C and light intensity of 1,000 lux. The effect of different superficial gas velocities on growth of H. pluvialis was evaluated within the range between 0.4 and 3 cm·s−1. It was found that growth of H. pluvialis was strongly affected by the superficial gas velocity. The maximum cell density and specific growth rate were obtained in the culture with the superficial gas velocity of 0.4 cm·s−1. These values are 77×104 cells mL−1 (2.79 g L−1 dry weight) and 0.45 day−1, respectively. Higher levels of gas velocity did not show any benefits, and in fact they were found to drastically slow down the growth, due to the increased shear stress. Further more an increase in superficial gas velocity could significantly change the cell morphology from motile vegetative cells to non-motile green cells or cysts.