Viability of freeze-dried cultures of lactic acid bacteria after storage for 30 to 40 years

摘要

The viability of Enterococcus durans, E. hierae, and Lactococcus lactis isolated from cheese has been determined after cultures were freeze-dried 30, 32, and 37 years ago, respectively. Survivors were counted in three media (Plate count, Elliker and BHI agars) by the pour plate method after 36 hours of incubation at 30 degrees C. Counts were also determined by the most probable number method using Elliker broth as the culture medium. The three strains were recovered, but the percent of viability differed substantially 0.3, 24, and 0.04%, respectively. It is confirmed once more that freeze-drying is a suitable method for long term storage of bacterial culture.