Antioxidant and antibacterial activities of sulphated polysaccharides from Pleurotus eryngii and Streptococcus thermophilus ASCC 1275

Polysaccharides from Pleurotus eryngii (PEPS) and exopolysaccharides from Streptococcus thermophilus ASCC 1275 (ST1275 EPS) were sulphated, and antioxidant and antibacterial activities of sulphated and crude polysaccharides were determined. Degree of sulphonation of PEPS and ST1275 EPS was 0.69 and 0.31, respectively. Characteristic bands in FT-IR spectra indicated that the sulphate group was at the C6 position of the galactose skeleton. Antioxidant activities of PEPS and ST1275 EPS were significantly (P < 0.05) improved after sulphonation. For tested crude and sulphated polysaccharides, sulphated PEPS had the largest inhibition zone against Escherichia coli ATCC 25922 and Staphylococcus aureus CMCC 26003 while sulphated ST1275 EPS had the largest inhibition zone against Listeria monocytogenes CMCC 54001. Furthermore, sulphated PEPS had the lowest minimum inhibitory concentration (MIC) for E. coli ATCC 25922, and both sulphated PEPS and sulphated ST1275 EPS had the lowest MICs on S. aureus CMCC 26003 and L. monocytogenes CMCC 54001.