Water molecules play important roles in enzymatic reaction especially for hydrolases, which use water as a substrate. Neutron crystallography is a powerful tool for visualizing hydrogen atoms to understand protonation states of protein and orientation of water molecules, while it requires a large-volume crystal (>1 mm3 ) compared with X-ray crystallography. To overcome the hurdle of crystal volume, a counter diffusion device equipped with 2 mm diameter can be used at the microgravity experiments. We report here the crystallization of two cellulases which hydrolyse glycosidic linkages in cellulose.
