Impact of salt stress on the α-tocopherol, carotenoid derivatives and flocculation efficiency of Euglena sp., Indonesian Strain

Tocopherol, carotenoids, and chlorophyll are the primary components of the antioxidative response in microalgae. Conditions
of stress, such salt stress, can trigger the processes responsible for the accumulation of tocopherol and carotene. It has been
found that the most difficult part of culturing microalgae is keeping it affordable. This study investigated the effects of different
salt types and concentrations on the amount of α-tocopherol, carotenoid derivatives, and flocculation efficiency of Euglena sp.
Cultures of Euglena sp. was developed under salt stress conditions of NaCl 200 mM and KCl 200 mM. UV-VIS spectrophotometry
was used to confirm the presence of α-tocopherol and carotenoid derivatives under thirteen days of salt stress testing. Increasing salinity has a significant effect on Euglena sp., causing spherical cell morphologies with aspect ratio 1.385 ± 0.031 for NaCl
200 mM and 1.414 ± 0.040 for KCl 200 mM. Increasing salinity also slowing down development with specific growth rate value of
0.171 ± 0.006 per day and 0.122 ± 0.029 per day for NaCl and KCl 200 mM, respectively. Nevertheless, the amount of α-tocopherol in Euglena sp. increases with a high salt concentration; algal cells flocculated more successfully when increasing the salt
concentrations (NaCl 200 mM and KCl 200 mM) was added. Due to the inhibition of photosynthetic activity in salt-stressed cells,
the control group exhibited higher levels of carotenoid derivatives (ranging from 0.5–1 μg/mL) and pheophytin a and b (0.0062
± 0.001 μg/mL and 0.0064 ± 0.001 μg/mL) than the group treated with salt stress. In conclusion, salt stress was an effective way
to raises the concentration of α-tocopherol and significantly reduce the expense of harvesting Euglena sp.