A novel exopolysaccharide produced by Zygosaccharomyces rouxii with cryoprotective and freeze-drying protective activities

•Exopolysaccharide (EPS-3791) from Zygosaccharomyces rouxii was purified.•The structures and properties of EPS-3791 were comprehensively elaborated.•EPS-3791 exhibited cryoprotective activity on L. lactis.•EPS-3791 exhibited freeze-drying protective effect on L. lactis. In the present work, a novel exopolysaccharide EPS-3791 was extracted and purified from a salt-tolerant yeast, Zygosaccharomyces rouxii. Structural analyses showed that EPS-3791 was composed of galactose, glucose and mannose in a molar ration of 1.00: 4.25: 13.30 with a molecular weight of 64.412 kDa. Fourier transform infrared spectroscopy manifested the main functional groups, α- and β- configurations. Methylated analysis indicated T-Manp-(1→, →2)-Glcp-(1 → and → 2,6)-Manp-(1 → were the main linkages. 800 MHz nuclear magnetic resonance spectroscopy demonstrated the EPS-3791 structure of a novel main chain and branched chain. Atomic force microscope and scanning electron microscope revealed a homogeneous and uniform porous structure. In addition, EPS-3791 was proven to have cryoprotective and freeze-drying protective effects on Lactococcus lactis, and exhibited better protective performance than that of trelahose during freeze-drying of L. lactis, suggesting that EPS-3791 could be developed into cryoprotectant or lyoprotectant applied in food industry.