A novel and high-efficiency supplementary lighting strategy to enhance the growth of Synechococcus sp. PCC 7002

Abstract

The objective of this study was to establish an effective night-time supplementary lighting strategy for improving the growth rate of Synechococcus sp. PCC 7002. Based on the indoor experimental data collected under varying light intensities, light qualities, light-dark cycle durations, and light-dark ratios, Response Surface Methodology (RSM) was employed to determine the optimal parameters for night-time illumination at different growth stages. The optimal culture conditions during the early growth stage (0–4 days) were identified as: light intensity of 140 μmol m⁻²·s⁻¹, red-blue light ratio of 2.6:1, light-dark cycle duration of 110 min, light-dark ratio of 6.3:1, and inoculation age of 6 days. For the middle growth stage (5–8 days), the culture conditions that produced the highest biomass concentration were: light intensity of 173 μmol m⁻²·s⁻¹, red-blue light ratio of 3.2:1, light-dark cycle duration of 116 min, light-dark ratio of 6.4:1, and inoculation age of 6 days. In the late cultivation period (9–12 days), no supplementary lighting was required. The indoor and outdoor cultivation were then compared under the different supplementary lighting strategies. The results demonstrated that the staged night-time supplementary lighting strategy achieved the highest biomass productivity under both indoor and outdoor conditions. During the initial 0–8 days of cultivation, the biomass productivity reached 0.58 g L⁻¹ d⁻¹ indoors and 0.50 g L⁻¹ d⁻¹, outdoors, more than 42.00 % higher than other lighting strategies. The staged, RSM-optimized night-time supplementary lighting strategy significantly improve the biomass concentration of Synechococcus sp. PCC 7002 while also reducing the overall light energy consumption.