Antioxidant properties and digestion behaviors of polysaccharides from Chinese yam fermented by Saccharomyces boulardii

A kind of novel polysaccharides from Chinese yam (Dioscorea opposita Thunb.) was prepared by fermentation with a fungal probiotic Saccharomyces boulardii. The preparation methods and parameters of fermented Chinese yam polysaccharides (FCYP) were optimized. Molecular weight and FT-IR spectrum of the optimized FCYP were also evaluated, along with its biological activities and digestion behaviors. Results showed that FCYP distributed in fermentation supernatant possessed the best total reducing power. On this basis, the highly active FCYP was obtained under the optimal fermentation conditions: fermentation time of 36 h, inoculation volume of 6% and solid-liquid ratio of 1:25 g/mL. Compared with unfermented Chinese yam polysaccharides (UCYP), the molecular weight of FCYP decreased prominently, accompanied with a significant increase of in vitro antioxidant activity. Meanwhile, FCYP also exhibited a favorable radioprotective effect at the cellular level. After in vitro simulated gastrointestinal digestion, FCYP remained relatively well bioactive stability, with lower molecular weight and the occurrence of lamellar morphological structure. Overall, Chinese yam polysaccharides fermented by S. boulardii were obtained with easier digestion and better functionality properties including antioxidant activity and radioprotection effect, which could be considered as one of health food components.