Exopolysaccharide (EPS) producing probiotic strain Enterococcus hirae KX577639 were isolated from the feces of South Indian Irula tribes. EPS yield was 18.57 g/L (dry weight) at 48 h in 2% sucrose supplemented MRS medium. TLC and GC-MS analysis confirmed the presence of predominant glucose monomer indicating the homopolysaccharide nature of EPS. FTIR and NMR studies revealed that the EPS were branched α-D-glucan polymer with α-(1 → 6) and α-(1 → 3) linkages. SEM analysis of glucan-EPS revealed porous and starch like cracked granules of aggregation. AFM studies proved spherical lumps and dense, grainy like network. The thermal behavior of glucan-EPS showed degradation temperature of 315.98 °C and melting point of 296.67 °C. The XRD analysis confirmed the amorphous nature of EPS with a crystalline index of 0.48. The water solubility index and water holding capacity of glucan-EPS showed 46.5% and 202.04%. These distinctive features of the glucan EPS could find its potential application in functional food products as the α-(1 → 3) linkage are resistant to human digestive enzymes and can serve as a nutrient to gut bacteria. This the first study reporting the EPS production by Enterococcus hirae.
Keywords: Enterococcus hirae; Exopolysaccharide; Feces; Irula tribes; Probiont; α-D-glucan.
Copyright © 2018 Elsevier B.V. All rights reserved.