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Abstract
SUMMARY :In developing a technique for the freeze-drying of lactobacilli particular attention was paid to the percentage survival rate; this was estimated by viable counts immediately after drying and after storage of the dried cultures. The main factor influencing survival rate was the suspending medium, the best results being obtained in horse serum with 8 % added glucose. Forty-four cultures, fourteen freshly isolated, representative of a comprehensive collection of 452 lactobacilli (see Briggs, 1953 a ) were freeze-dried in this vehicle using the apparatus and technique described. The majority of the survival rates were over 50 % immediately after drying, and over 25 % after 6 months storage; all but two of the freshly isolated strains dried well. Some of the dried cultures were tested again after a storage period of about 2 years and then showed satisfactory percentage survivals.
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