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

•EPS22 from Pseudomonas stutzeri AS22 was used as a source of various Mw-derivatives (EDP).•EDP shared similar constitutive sugars and differed in their proportion and Mw.•EDP Mw-activity relationship was investigated.•High Mw EDP showed stronger antibacterial effects against Gram-negative bacteria and the opposite trend was observed for Gram-positive bacteria.

Many researchers have focused on high molecular weight (Mw) exopolysaccharides (EPS) as a source of potentially bioactive lower Mw 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 Mw, 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.