Shelf-life extension of freeze-dried Lactobacillus brevis WiKim0069 using supercooling pretreatment

Shelf-life extension of freeze-dried lactic acid bacteria is important for reducing distribution costs. Herein, effect of cold adaptation prior to freeze drying on the storage stability of freeze-dried Lactobacillus brevis WiKim0069, a kimchi starter, was investigated under supercooling at -5 degrees C without ice crystal nucleation and formation. Cold adaptation at 10 degrees C was used as a reference. Cold adaptation caused an increase in surface layer protein and improved cell viability. The surface layer of cold-adapted cells was substantially thicker than that of non-adapted cells, with supercooling inducing the strongest effect. Cold adaptation increased the viability of L. brevis WiKim0069 during and after 56-day storage. After 56 days of storage, the highest viability of 81.2% was observed with supercooling pretreatment. The addition of surface layer protein during cold adaptation further promoted viability, supporting the role of surface layer protein. These results suggest that supercooling pretreatment can be useful for extending the shelf-life of L. brevis WiKim0069.