Lypholization is a freeze-drying technique for preservation and storage of bacteria and other microorganisms. Bacteria can be stored for extended periods of time (three to five years) as frozen cell suspensions or as freeze-dried (lypholized) cultures. This technique is achieved by placing bacteria in a nutrient broth containing 15 to 25 percent glycerol and freezing at temperatures of -94°F (-70°C) or lower. The glycerol reduces ice crystal formation that would cause subsequent cell damage and disrupt biological structures.