Identification and characteristics of Pantoea cypripedii 4A strain producing high molecular exopolysaccharide

Abstract

Searching for new microorganisms with great potential for the synthesis of high-molecular exopolysaccharides possessing some useful traits is very important in the scope of certain industries. The bacterial strain Pantoea cypripedii 4A isolated by direct plating on a rich agar medium was studied in this work as a potential producer of extracellular polysaccharides. This strain was isolated from forest litter mixed with the topsoil of the M.A. Zablotsky Prioksko-Terrasny Reserve. The Pantoea cypripedii 4A strain is capable of synthesizing EPS that was confirmed by the Podobedov-Molish reaction (a qualitative reaction to carbohydrates in the medium) on a medium supplemented with 5% sucrose. Gel permeation chromatography confirmed that the isolated strain produces an exopolysaccharide with a molecular weight of about 1.69 MDa on a medium supplemented with 5% sucrose. However, the presence of two lower molecular weight peaks may indicate that the resulting product has heterogeneous structure. The yield of dry biopolymer when growing the strain on a mineral medium with sucrose at a final concentration of 5% without adding additional components, such as microelements, was 8.5 g/l. One of the important characteristics of EPS is the viscosity of their aqueous solutions. The measured dynamic viscosity of a 10% EPS solution synthesized by Pantoea cypripedii 4A was 1.728 mPa s. Despite the fact that the production of extracellular polysaccharides is often enhanced under stress conditions, neither reduced oxygen concentration, nor low temperature conditions did affect the EPS biosynthesis by the studied strain.