Depolymerization of Pseudomonas stutzeri exopolysaccharide upon fermentation as a promising production process of antibacterial compounds

Abstract

Many researchers have focused on high molecular weight (M_w) exopolysaccharides (EPS) as a source of potentially bioactive lower M_w derivatives. Therefore, it is of interest to find means for efficient and safe production of depolymerized-polymer derivatives. Exopolysaccharide-depolymerization products (EDP) varying in molecular weight were recovered from fermentative depolymerization of a native EPS produced by Pseudomonas stutzeri AS22. Following their purification and physicochemical characterization, the antibacterial activity of EDP on food spoilage and food poisoning microorganisms was evaluated through the measurement of the inhibition zone diameter, the half maximal (IC₅₀) and the minimal (MIC) inhibitory concentrations. Our results indicate that the lower the M_w, the higher will be the effectiveness of EDP on reducing Gram-negative bacteria growth and the opposite trend was observed in the case of Gram-positive bacteria. EDP bioactivities may provide novel insights into the potentiality of P. stutzeri EPS and its derivatives to be used as functional-food components.

Keywords: Antibacterial activity; EPS-derivatives; Exopolysaccharide; Fermentative depolymerization; Molecular weight; P. stutzeri AS22.