Fig. 5. SEM images of S. thermophilus after freezing at −20 °C for 24 h and 2 freezing–thawing cycles with different cryoprotectants.

The concentration of rsfAFP was 0.1 mg/mL. 20 mM PBS was used as s negative control; 15% glycerol, 1.0 mg/mL sucrose were used as the positive controls. Green arrow: damaged cells; red arrow: ruptured cells.