Protective effects of β-glucan extracted from spent brewer yeast during freeze-drying, storage and exposure to simulated gastrointestinal conditions of probiotic lactobacilli

This study aimed to evaluate the potential of spent brewer yeast beta-glucans (Y beta G) as a protective agent of probiotic Lactobacillus cultures (L. acidophilus LA-05, L. plantarum 49, and L. plantarum 201) during freeze drying, storage (4 degrees C, 120 days) and in vitro digestion. The membrane integrity and cell ultra-structure of probiotics were also evaluated. An established cryoprotectant (Fructooligosaccharides, FOS) was used for comparison. beta-glucan acted as a cryoprotectant for probiotic lactobacilli during freeze-drying, refrigerated storage (90 days) and simulated gastrointestinal conditions (SGIC), in a similar manner to that of FOS. However, after 90 days of storage time, FOS provided a higher protection and resulted in cells with lower membrane damage. The effect of the cryoprotectants and the resistance to the SGIC varied with the strain tested. Y beta G performed better as cryoprotectant toward L. plantarum 201. The micrographs showed that L. plantarum 201 could adhere to Y beta G surface and produce exopolysaccharides. This study demonstrated that a beta-glucan extracted from spent brewer yeast could be used as a cryoprotectant for probiotic lactobacilli during freeze-drying, refrigerated storage and exposure to SGIC.