Effect of biomass concentration on the productivity of Tetraselmis suecica in a pilot-scale tubular photobioreactor using natural sunlight

The effect of biomass concentration on the net volumetric productivity, yield on light and nightly biomass loss rate of Tetraselmis suecica was studied using a pilot-scale tubular photobioreactor (PBR) under outdoor light conditions. The net average productivity and yield on light of Tetraselmis suecica were optimal at a biomass concentration of 0.7 g L-1. Cultures grown at higher biomass concentrations showed a prolonged respiration period at low light periods, while light was wasted in more dilute cultures at high light intensities. At optimal biomass concentration of 0.7 g L-1 the highest average net productivity and yield on light were 0.35 ± 0.03 g L-1 d-1 and 1.19 ± 0.15 g mol-1, respectively. The highest nightly biomass loss rate was measured for Tetraselmis suecica grown at an optimal biomass concentration, which can be explained by higher maintenance costs of the microalgae with a higher growth rate. This study shows that the productivity and yield on light can be enhanced by optimizing the biomass concentration.