Cryopreservation of the anaerobic rumen fungus Neocallimastix patriciarum

Neocallimastix patriciarum was successfully frozen in liquid media containing 5% dimethylsuphoxide as cryoprotectant. Initial freezing and storage for 24 h in solid CO2 before transfer to liquid N2 was necessary for survival. Long‐term storage under liquid N2, solid CO2 and at ‐ 80°C was tested; only storage in liquid N2 proved successful for periods in excess of several months. Analysis of metabolic end‐products and electron microscopy indicated that no morphological or biochemical changes had occurred in cultures preserved for 1 year. Piromonas communis and a recent isolate from the ovine rumen were preserved under the same conditions. The method does not require controlled freezing equipment, making it an easily applied laboratory technique