Novel hydroxyectoines based formulations are suitable for preserving viability of Limosilactobacillus fermentum, Levilactobacillus brevis SP-48 and Bifidobacterium lactis HN019 during freeze-drying and storage, and in simulated gastrointestinal fluids

This study aimed at evaluating the influence of compatible solutes such as ectoine and hydroxyectoine (HOE), on bacterial cell viability during freeze-drying and storage (at 4 degrees C and 25 degrees C), in comparison to the well-established use of trehalose. Three strains, namely Limosilactobacillus fermentum, Levilactobacillus brevis SP-48, and Bifidobacterium lactis HN019 were used as models demonstrating that the highest survival rate during freeze drying was observed for cells protected with HOE. Although trehalose was more effective during lyophilization, interestingly the combination of trehalose and HOE most efficiently preserved long-term cell viability (viability loss < 0.5 log units after 6 months of storage). Finally, the ability of HOE to contribute to strain resistance in simulated gastrointestinal juices was evaluated and the latter protected all the strains tested more efficiently than all the other solutes, in particular the viability was improved from 58%, 87.5%, and 94% when cells were dried with saline solution to 88%, 98.3%, and 98% when lyophilized with HOE for L. fermentum, L. brevis, and B. lactis, respectively. In conclusion, the addition of HOE to trehalose improves the stability of probiotics during storage and enhances the survivability in simulated gastrointestinal tract conditions.