Purification and structural-functional characterization of an exopolysaccharide from Bacillus licheniformis PASS26 with in-vitro antitumor and wound healing activities

The exopolysaccharide (EPS) synthesized by Bacillus licheniformis PASS26, a salt pan inhabiting bacteria was successfully purified. This is the first report to reveal its structural-functional properties and biological activities. The low molecular weight (56 kDa) polysaccharide was analyzed for monosaccharide composition with TLC and HPLC. The analyses confirmed the hetero-polymeric nature of EPS with 18.44% glucose, 9.89% galactose, 16.15% fructose, 27.32% mannose and 28.18% galacturonic acid. Morphological study by scanning electron microscopy demonstrated less porous flakes like structure. Elemental analysis revealed the presence of a small quantity of nitrogen, indicating a partially charged nature of the polysaccharide. The X-ray diffraction pattern and differential scanning calorimetric (DSC) observations reflected semi-crystalline nature. Thermal gravimetric analysis (TGA) and rheological studies displayed moderate thermal stability over a range of 30-350 °C and semi-viscous nature respectively. Studies on functional properties displayed concentration-dependent water soluble nature of EPS with good water (98.8%) and oil (101.7%) holding capacity. The EPS acquired moderate emulsification activity with excellent stability against all the food grade oils and hydrocarbons tested. Studies revealed interesting in-vitro anti-tumor activity and wound healing efficiency. EPS showed significant functional and biological properties for potential applications in food and pharmaceutical industries.