Controlling average number of photons received per biomass to promote the growth of Synechocystis sp. PPC 6803.

To investigate the actually received light of cells in the photo bioreactor, a light attenuation model of Synechocystis sp. PCC 6803 was established. The relationship between the average number of photons received per biomass (APRPB) and the growth of cell was analyzed. The results demonstrated, Cornet model was accurately fitted with the light attenuation of Synechocystis sp. PCC 6803 and the cell growth rate was affected by APRPB. When the value of APRPB is 3.2 μmol g-1 s-1, the cell have the maximum light efficiency. A maximum specific growth rate of 0.05 h-1 was achieved with APRPB from 3.2 to 12.8 μmol g-1 s-1. After 156 h cultivation, compared to cells cultured under constant light [light intensity: 100 and 1800 μmol/(m2 s)], the DCW under controlled light intensity (light intensity increasing with the cell density) was higher by 79.1% and 20.0%, respectively. This study indicated that APRPB could be used as a light intensity regulation criterion to improve cell production despite different types of reactor and cell density, which provided a theoretical basis for improving the biomass yield of Synechocystis sp. PCC 6803 or other photosynthetic auto-trophic organism.