2.3 Functional groups and cell morphology
The algal sample was centrifuged and stored in a refrigerator for
freeze-drying. Then, the functional groups were analyzed by ATR-IR
(Nicolet iS5 FTIR, USA) [16]. The centrifuged cells were fixed with
ethanol and freeze-dried with acetone. The samples were stored for SEM
(Zeiss-Supra55) analysis [2]. For TEM (Tecnai G2 F20S-TWIN + AZtec
X-Max 80T) observation, the samples were first fixed with glutaraldehyde
and then stored at 4 oC. Finally, ultrathin (60–80
nm) was cut by a diamond knife for TEM analysis [26].