Effects of Cross Stress on the Survival of Lactiplantibacillus plantarum LIP-1 After Freeze-Drying

Abstract

Appropriate single-stress treatment can improve the resistance of lactic acid bacteria against freeze-drying. However, whether the combination of two stresses can further enhance their resistance warrants exploration. This study examined the effects of cross stress on the resistance of the Lactiplantibacillus plantarum LIP-1 strain against freeze-drying. Compared with oxygen or cold stress alone, cross stress increased the post-freeze-drying survival rate of L. plantarum LIP-1 to 84.98% (P < 0.05). After 8 weeks of room-temperature storage, the count of live bacteria could still be maintained at 6.27 × 10⁹ CFU/g. Mechanistic analyses revealed that the strain treated with cross stress could synthesize more protective biofilms and surface proteins, which significantly reduced cell wall damage. Furthermore, owing to the combined effect of two single stresses, cross stress could enhance the strain’s antioxidant capacity, reduce the production of reactive oxygen species, inhibit the oxidation of fatty acids in the cell membrane, and maintain the integrity and fluidity of the cell membrane. In addition, cross stress treatment increased the intracellular pH, effectively reducing the degree of DNA damage. These factors significantly improved the survival rate of L. plantarum LIP-1 after freeze-drying.