Novel nano-particulated exopolysaccharide produced by Klebsiella sp. PHRC1.001.

In recent decades, microbial synthesis of polysaccharides with special functional properties has attracted increasing attention. This work reported a novel exopolysaccharide (EPS)-producing strain, Klebsiella sp. PHRC1.001 isolated from activated sludge. Physicochemical, rheological, emulsifying and toxicological properties of the obtained EPS were characterized. The EPS was mainly composed of d-glucose and l-arabinose, and was found to exist in aqueous solution in a nano-particulated form (∼50nm in diameter) with a strong tendency of aggregation. Rheological analysis showed that the EPS aqueous solution was a typical pseudoplastic fluid at higher concentration and could form weak gel upon alkaline treatment followed by neutralization. The EPS exhibited excellent emulsifying properties in stabilizing oil-in-water emulsions presumably by a Pickering mechanism owing to its nanoparticle structure. Acute toxicity test showed that 1.8g EPS per kg of body weight caused no toxic effect on mice. PHRC1.001 EPS has the potential to be a novel industrial polysaccharide.