We are growing Azotobacter in liquid medium and can't obtain cysts after fermentation. We tried to use minimal salt medium, tried to mix the obtained liquid with other materials such as butanol, glycerol, liquid humus, starch, gum arabicum, PVP but no formation of cysts we can observe. Furthermore the number of colony forming units are decreasing very faster, i.e. during storage of one month the number of CFU 109 decrease until 108. Maybe someone can suggest some methods how to induce cyst formation of Azotobacter vinelandii in liquid medium and how to keep the number of cells for a long storage?