Cryopreservation of suspension cultures of Camptotheca acuminata

Suspended cells of Camptotheca acuminata were observed to lose their ability to synthesize camptothecin and its derivatives as a result of repeated cultures. Accordingly the maintenance of high-yield cells by cryopreservation was studied to overcome this stability problem, and various factors involved were optimized. Pregrowing the cells in 8% myoinositol for 4 days was found to be the most effective in improving survival. The highest survival was obtained when the pregrown cells were cryoprotected with a mixture of 10% DMSO, 0.6 M mannitol, and 10% glycerol. When the cryopreserved cells were maintained in a freezer at -70 degrees C, 94% survival was obtained after 4 months. The survivals after 5 and 8 months of storage decreased to 52% and 45%, respectively. No loss of biosynthetic capability of camptothecin was observed after short to medium term cryopreservation of C. acuminata.