3.3. Effects of Different wavelengths on the Growth of FACHB-314
The effect of rGO-TiO2 nanoparticles on the growth ofFACHB-314 under different wavelengths of light was experimentally studied. Analyzed 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 7. In the medium without adding nanoparticles, the dry cell weight ofFACHB-314 under red light is only 0.58 g/L, and the dry cell weight under white light increased to 1.73 g/L. Compared with red light, the weight of stem cells has increased by nearly three times. The increment of stem cells under red right indicates that FACHB-314is very sensitive to light of different wavelengths, and white light is more conducive to the growth of FACHB-314 due to the capture and absorption of light energy through the first step of photosynthesis. For the full use of the energy in sunlight, photosynthetic organisms have formed an effective light-absorbing device, which is composed of photosynthetic pigments that absorb different wavelengths during the evolution process. The device can effectively capture the energy of visible light and near-infrared light. Therefore, the decrease in the dry cell weight of FACHB-314 can be attributed to the reduction of the wavelength range, which reduces the absorption of light energy by photosynthetic pigments and reduces the accumulation of photosynthesis in FACHB-314 , which indicates that the growth of FACHB-314is slow.
The results in Table 1 show that the dry cell weight of the control group under white light is 1.73 g/L, and the stem cell yield is 0.186 g/L/d. In the medium supplemented with TiO2nanoparticles, the dry cell weight of FACHB-314 reached its maximum on the 9th day, which was 1.47 g/L, and the dry cell weight yield was 0.154 g/L/d. Compared with the blank control group, the dry weight of FACHB-314 cells decreased by 15.0%, and biomass productivity decreased by 18%. The results show that TiO2 nanoparticles have a certain inhibitory effect on the growth of FACHB-314 . However, in the medium supplemented with rGO-TiO2 nanoparticles, the dry cell weight ofFACHB-314 reached its maximum on the ninth day at 1.66 g/L, and the dry cell weight yield was 0.178 g/L/d. Compared with the control group, there is no significant difference between the dry cell weight ofFACHB-314 and its stem cell yield, which indicates that rGO-TiO2 nanoparticles have no significant effect on the growth of FACHB-314 .
Under the condition of red-light irradiation, the cell growth ofFACHB-314 was significantly inhibited, and the cell growth trend of the two experimental groups added with nanomaterials was significantly higher than that of the control group, and the biomass of the rGO-TiO2 composite nanoparticles was the highest. Under the red-light condition, the dry cell weight of the control group was 0.58 g/L, and the dry cell weight yield was 0.053 g/L/d. Compared with the white light culture condition, the biomass of FACHB-314was significantly reduced by 198%. This indicated that the red wavelength light significantly inhibited the growth of FACHB-314cells. The dry cell weight of FACHB-314 reached its maximum value on the ninth day of the medium supplemented with TiO2nanoparticles, and it was 1.29 g/L, and its dry cell weight yield was 0.141 g/L/d. Compared with the control group, its dry cell weight increased by 0.71 g/L, an increase of 122.4%, and its dry cell weight yield increased by 166%. On the medium with rGO-TiO2composite nanoparticles, the dry cell weight of FACHB-314 reached the maximum value of 1.39 g/L on the ninth day, and the dry cell weight yield was 0.154 g/L/d. Compared with the control group, the dry cell weight increased by 0.81 g/L, an increase of 139.7%, and the dry cell weight yield increased by 191%. The above results show that under monochromatic red-light irradiation, the experimental group adding rGO-TiO2 composite nanoparticles can significantly increase the utilization of red light in the photosynthetic system ofFACHB-314 , and thus can greatly increase the growth ofFACHB-314 cells. Compared with FACHB-314 with TiO2 nanoparticles added with rGO-TiO2nanoparticles, under white light, the dry cell weight ofFACHB-314 increased by 0.19 g/L, an increase of 12.9%, and its dry cell weight yield increased by 0.024. g/L/d; under red light, its dry cell weight increased by 0.10 g/L, an increase of 7.8%, and its dry cell weight yield increased by 0.013 g/L/d. In summary, the biomass ofFACHB-314 added with rGO-TiO2 nanoparticles was higher than that of the experimental group with TiO2nanoparticles under two different wavelengths of light conditions.