Maintenance of Lactic Acid Bacteria

Freeze-drying is commonly used for the long-term preservation and storage of microorganisms in stock collections as well as for the production of starter cultures for the food industry. The choice of an appropriate suspending medium is of primary importance to increase the survival rate of the lactic acid bacteria (LAB) during and after freeze-drying although the success of the process also depends on several factors such as growth phase, extent of drying, rehydration, suspension medium, cryoprotectors, and so forth (1 –3 ). During freezing or freezedrying, cellular damage may occur, resulting in a mixed population containing unharmed cells and dead cells as well as those sublethally injured. Damage may not lead directly to death since in a suitable environment the injured cells may repair and regain normal functions (4 ,5 ). Information on the requirements for recovery from sublethal injury is important from the standpoint of food microbiology and culture collections.