3.4.8. Biological Activity

The bioactivity of the selected emulsions was determined using an environmental cell metabolic activity test of the *Lactobacillus* sp. 2675 strain. The test was performed according to the methodology described by Pacholak et al. (2019). In these assays, 0.25 mL of the emulsion, 0.25 mL of the cell suspension in a nutrient broth (OD600nm ca. 1.0 after 24 h of incubation at 30 ◦C) and 0.05 mL of the MTT indicator solution (5 mg/mL) were used. After 24 h of incubation, the reduction of yellow MTT into its purple formazan, which is catalyzed by cellular respiratory pathway enzymes, was measured. The samples in which the emulsion was replaced with deionized water were used as the reference sample.
