Effect of skim milk coated inulin-alginate encapsulation beads on viability and gene expression of Lactobacillus plantarum during freeze-drying

• Lactobacillusplantarum was encapsulated in ISA before freeze-drying.
• ISA encapsulated L. plantarum showed better survival rate compared with free cells.
• Beneficial functionality of ISA encapsulated L. plantarum was improved.

The goal of this study was to evaluate the viability and gene expression relating to probiotic functionality of encapsulated Lactobacillus plantarum CCTCC M 2014170 during freeze-drying. Sodium alginate with or without inulin was applied as an inner layer and skim milk was used as an outer layer for coating sodium alginate particles. The results indicated that skim milk coated inulin-sodium alginate (ISA) encapsulation beads improved the survival of L. plantarum during exposure to adverse environment. The viability of L. plantarum from ISA encapsulation beads did not change after 2 h incubation in simulant gastric fluid (SGF). In 1% bile salt solution, the L. plantarum from ISA encapsulation beads only had 1.21 log CFU/mL reduction after 2 h treatment. After 7 weeks storage, the survival rate of L. plantarum was 20.89%, which showed reduction from 8.52 to 7.84 log CFU/mL. In addition, all genes relating to probiotic functionality of L. plantarum were similarly but not significantly up-regulated except the plnEF, which exhibited the highest up-regulation at more than 17-fold increase. This study indicated that encapsulation with alginate and skim milk in the presence of inulin before freeze-drying protected and improved the probiotic functionality of L. plantarum from the adverse freeze drying environment.