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.