Abstract. The aim of this study was to evaluate the efficacy of whey protein isolate (WPI) as an encapsulation matrix for improvement of L. fermentum 39-183 viability to low pH and bile and releasing the encapsulated bacteria in ex vivo porcine gastrointestinal (GI) contents. 1g of protein microcapsules (≈ 10 8 CFU of L. fermentum 39-183 or E. coli GFP + ) were incubated in ex vivo porcine GI contents (9 mL) under anaerobic conditions at 37 0 C. Results showed that there was higher than 86 % cell survival for encapsulated L. fermentum 39-183 after 3 h incubation in pH 2.0, whereas free cell experienced complete viability loss. Encapsulated L. fermentum 39-183 showed only about 0.86 log reduction for all bile salt levels tested (0.5 ÷ 2.0 %), while 3.34 log decrease of free cell after 6 h of incubation. There was almost a complete release (3.9 × 10 8