Fig. 4. SEM images of the conversion products without adding amino acids (a) and with adding different amounts (0.05 g, 0.1 g and 1 g) Gly, Arg and Glu respectively after soaked in 0.15 M K₂HPO₄ with pH 10 at 37 °C for 10 d. The inserts in the upper right corner are close-up images.