Cultivation of a cyanobacterium in an internally radiating air-lift photobioreactor

Abstract

This study proposes a new design of the internally radiating photobioreactor, which combines the advantages of an air-lift bioreactor and an internally radiating system, and an efficient way of supplying light energy into the photobioreactor during cell cultivation. For a model photosynthetic microorganism, Synechococcus PCC 6301 was cultivated in an internally radiating air-lift photobioreactor. The light condition inside the photobioreactor was characterized by the average light intensity which was calculated from the light distribution model. Since excessive light energy induced photoinhibition at the early growth stage, the strategy of lumostatic operation was developed in order to maintain the light condition at an appropriate level during cell cultivation. Based on the calculation results of the light distribution model, the average light intensity was regulated at 30, 60, or 90 mu mol m(-2) s(-1) by increasing the number of light radiators. The model-based control of irradiating level enabled us to harvest a larger amount of cells without showing the photoinhibited growth. Other favorable results included the reduction of cultivation time and lower consumption of irradiating power.