Production of water-soluble sulfated exopolysaccharide with anticancer activity from Anoxybacillus gonensis YK25

Abstract

BACKGROUND: Thermophilic bacteria are accepted as novel sources of exopolysaccharides (EPSs) with different biological activities. This study was conducted to test EPS production potential of thermophilic bacteria isolated from hot springs in Erzurum province (Turkey), to optimize EPS production from the best isolate in molasses medium, to characterize the produced EPS, and to investigate its anticancer activity. RESULTS: Among 28 isolates, the best EPS producer isolate was found to be Anoxybacillus gonensis YK25 (GenBank No: MN865832). Under optimized culture conditions (initial pH 7.0, temperature 55 °C, molasses concentration 100 mL/L, peptone concentration 6 g/L, and incubation time 96 h), 4.4 g/L EPS was produced. Molecular weight of EPS was 102 kDa. Carbohydrate and protein contents of EPS were 91.4% and 4.1%, respectively. EPS was a heteropolysaccharide containing xylose (59%), sucrose (18%), glucose (16%), and galactose (5%). It had a high solubility in water and a moderate solubility in dimethyl sulfoxide (DMSO), but it was insoluble in polar solvents. FTIR analysis confirmed the presence of hydroxyl, carboxyl, amide, and sulphate groups. EPS showed anticancer activity against SHSY-5Y, HT-29, DU-145, and A-549 cell lines in a dose-dependent manner. The IC50 values of EPS for A-549, DU-145, SHSY-5Y, and HT-29 cancer cells were 5.5, 9.61, 15.62, and 17.35 mg/mL, respectively. CONCLUSION: The EPS production potential of A. gonensis, and the anticancer activity of the produced EPS were revealed. Furthermore, it was shown for the first time that the main monomer of bacterial heteropolysaccharides would be xylose. This study indicates that Anoxybacillus species may be a novel source of pharmaceutically-important EPSs. © 2020 Society of Chemical Industry. © 2020 Society of Chemical Industry