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

Abstract

This study aimed to evaluate the potential of spent brewer yeast β-glucans (YβG) as a protective agent of probiotic Lactobacillus cultures (L. acidophilus LA-05, L. plantarum 49, and L. plantarum 201) during freeze drying, storage (4 °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. β-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. YβG performed better as cryoprotectant toward L. plantarum 201. The micrographs showed that L. plantarum 201 could adhere to YβG surface and produce exopolysaccharides. This study demonstrated that a β-glucan extracted from spent brewer yeast could be used as a cryoprotectant for probiotic lactobacilli during freeze-drying, refrigerated storage and exposure to SGIC.