2.5. Scanning electron microscopy analysis
Freeze-dried samples were cut with a razor blade and cut sur-face samples were prepared by sticking onto double-sided adhesivetape attached to a circular specimen stub. The samples were viewedusing an environmental scanning electron microscope (ESEM)(Quanta200F, FEI Deutschland GmbH, Kassel, Germany) at 30 kVand 3.0 spot size (Chen et al., 2012).