Characterization of a novel galactan produced by Weissella confusa KR780676 from an acidic fermented food

• EPS-producing Weissella confusa KR780676 was isolated from Idli batter with a higher yield of 17.2 g/L.
• EPS is composed of linear galactan containing α-(1 → 6)-linked galactose units.
• Microstructure of EPS shows the presence of porous and spongy starch-like granules.
• EPS is in semi-crystalline nature and also having high thermal stability.
• EPS with high water solubility reveals potential application as food hydrocolloids.

An exopolysaccharide (EPS) producing strain PUFSTM055 isolated from Idli batter (an Indian traditional cereal-legume based fermented food) was identified as Weissella confusa KR780676. The strain was shown to produce 17.2 g/L (dry weight) of EPS in 2% sucrose supplemented MRS broth and the EPS was characterized. HPTLC analysis confirmed the presence of galactose monomers, indicating the homopolysaccharide nature of EPS. Fourier-transform infrared spectroscopy and nuclear magnetic resonance analysis revealed that the EPS was found to be a novel linear galactan containing α-(1 → 6)-linked galactose units. Scanning electron microscopy of the EPS revealed the presence of porous and spongy starch-like granules. Topographical examination of EPS by atomic force microscopy revealed that the EPS formed densely packed mesh-like structure with irregular spherical lumps. The EPS also showed high thermal stability with a degradation temperature of 287.5 °C and melting point at 274.65 °C. EPS was semi-crystalline with crystallinity index of 0.23 and showed 100% water solubility index. These characteristics of the EPS would make it a promising hydrocolloid for food industries as bio-thickeners, stabilizers and also as an encapsulating material for delivery of food bioactive compounds. This is the first study reporting the galactan compose of the EPS from lactic acid bacteria.