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

Abstract

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 (56kDa) polysaccharide was analyzed for monosaccharide composition with TLC and HPLC. The analyses confirmed the hetero-polymeric nature of EPS with 18.44 percent glucose, 9.89 percent galactose, 16.15 percent fructose, 27.32 percent mannose and 28.18 percent 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 degrees C and semi-viscous nature respectively. Studies on functional properties displayed concentration-dependent water soluble nature of EPS with good water (98.8 percent) and oil (101.7 percent) 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.