3.6. Effects of Different Light and Dark Cycles on the Growth and Phycocyanin Content of FACHB-314
The light-dark control group chooses full light (lighting time: dark time = 24h: 00h) and half-light time (lighting time: dark time = 12h: 12h) for comparison (Lamminen et al., 2017). During these two periods of light and darkness, adding nanoparticles to FACHB-314 alters growth. The growth curve in Figure 11(a) shows that different nanoparticles have a certain effect on the growth of FACHB-314 in a different light and dark periods.
Analyze the growth data of each group of FACHB-314 . On day 9 of the culture, the dry cell weight and biomass yield results of the three groups of FACHB-314 are shown in Figure 11(b). In the control group, the dry cell weight of FACHB-314 under half-light was only 1.00 g/L, while the dry cell weight under full light increased to 1.73 g/L, which was nearly doubled compared to half-light. This indicates that the growth of the spiral depends on the light time, and a longer light time is more beneficial to the growth of FACHB-314 . This is due to the increased photoreaction time of photosynthesis ofFACHB-314 , which accumulates more organic matter, which promotes its growth.
The effect of rGO-TiO2 nanoparticles on the growth of three groups of FACHB-314 under half-light. The growth trend of the experimental group with TiO2 nanoparticles was like that of the control group, and the biomass of FACHB-314 with rGO-TiO2 nanoparticles was higher than that of the control group. The dry cell weight of the control group with nanoparticles added under half-light was 1.00 g/L, and the dry cell weight yield was 0.098 g/L/d. In the medium supplemented with TiO2 nanoparticles, the dry cell weight ofFACHB-314 reached its maximum value on the ninth day and was 0.90 g/L, and its dry cell weight yield was 0.085 g/L/d. The dry cell weight of FACHB-314 reached its maximum value on the ninth day of the medium supplemented with rGO-TiO2 nanoparticles, and it was 1.17 g/L, which was an increase of 17.0% compared with the control group; its dry cell weight yield It was 0.119 g/L/d, which was an increase of 21.4% compared with the control group. Compared withFACHB-314 with TiO2 nanoparticles added with rGO-TiO2 nanoparticles, the dry cell weight increased by 20.0% and the dry cell weight yield increased by 40.0% under half-light. The above results show that under the two different light and dark cycle conditions, the biomass of the experimental group with rGO-TiO2 nanoparticles is higher than that of the experimental group with TiO2 nanoparticles, and the growth of FACHB-314 under half-light is obvious enhancement.
The results in Figure 11(c) and Table 3 show that during the semi-light culture, the phycocyanin content of FACHB-314 and nanoparticles is always lower than the cumulative amount under the full-light culture. It can be found that FACHB-314 cultivated with nanoparticles is not conducive to the accumulation of algal protein in the half-light. (c) shows that the maximum intracellular phycocyanin content ofFACHB-314 cultured in the absence of light is 38.7 mg/g, and the yield is 38.70 mg/L. Compared with full light, the content and yield of phycocyanin were reduced by 48.5% and 52.7%, respectively. Similarly, in the two experimental groups where nanoparticles were added, the decrease in phycocyanin content and the decrease in phycocyanin production also had different degrees.