Development and Protective Mechanism of a Freeze-Drying Protectants Against Freeze-Drying for Lactiplantibacillus plantarum W1

Abstract

Lactiplantibacillus plantarum (L. plantarum) has promising applications in the development of probiotics, largely based on its recently recognized role in the gut–heart–brain axis. However, its survival rate after freeze-drying and its storage stability are key factors limiting the development and application of L. plantarum. In this study, we mixed skimmed milk, trehalose, and inulin (SMTI) in a 1:8 mass ratio with L. plantarum W1, followed by freeze-drying. The results showed that using SMTI as a protectant could increase the freeze-dried survival rate to 86.87%+0.9%. After 1 month, the viability of the freeze-dried bacterial cells was 2.87+0.44×10⁹ CFU/g. By measuring relevant enzyme activities, we found that the addition of this protectant enhanced the activity of Na⁺-K⁺-ATPase, Ca²⁺-Mg²⁺-ATPase, and total ATPase during freeze-drying. These enzyme activities maintained the integrity of the L. plantarum W1 cell membrane and reduced the leakage of lactate dehydrogenase and β-galactosidase. Therefore, SMTI improved the freeze-dried survival rate of L. plantarum W1 and increased its resistance to adverse conditions. Our study provides a new formula for a probiotic protectant, offering a new method by which to preserve probiotic strains during freeze-drying.