Semi-continuous cultivation strategy for improving the growth of Synechocystis sp. PCC 6803 based on the growth model of volume average light intensity

To develop a semi-continuous cultivation strategy to improve the growth of Synechocystis sp. PCC 6803, the growth model of volume average light intensity (VALI) was established based on the light attenuation curve and the cell growth rate under different light intensities. According to the growth model, the semi-continuous cultivation strategy was optimized by controlling microalgal cells under the optimal VALI closed to 115 μmol m−2 s−1 in the culture process. The accuracy of growth model prediction and the cultivation effect of semi-continuous strategy were both verified under indoor conditions. The microalgae grew well when the VALI was in the range of 109–121 μmol m−2 s−1 (the 3rd day as a semi-continuous start replacement point, one-day replacement). The maximum total biomass was 3.36 ± 0.09 g and increased by 86.67 % compared with that without the semi-continuous cultivation strategy (1.80 ± 0.07 g). Subsequently, the microalgae were cultured in different ranges of VALI to further verify the cultivation effect of the semi-continuous strategy. The results once again confirmed that the cell growth was more favorable when the VALI was controlled in the range of 109–121 μmol m−2 s−1. Finally, the semi-continuous cultivation strategy was conducted by controlling VALI under outdoor conditions. The results showed that the maximum total biomass was 289.19 % higher than that without the semi-continuous cultivation strategy. This study indicated that the semi-continuous culture strategy of controlling the VALI in an appropriate range could accelerate the growth of Synechocystis sp. PCC 6803 in outdoor culture, and provided an important experimental basis for the large-scale culture of Synechocystis sp. PCC 6803 outdoors.