Exopolysaccharides from probiotic bacteria and their health potential

Abstract

Exopolysaccharides (EPS) are extracellular macromolecules excreted as tightly bound capsule or loosely attached slime layer in microorganisms. They play most prominent role against desiccation, phagocytosis, cell recognition, phage attack, antibiotics or toxic compounds and osmotic stress. In the last few decades, natural polymers have gained much attention among scientific communities owing to their therapeutic potential. In particular the EPS retrieved from probiotic bacteria with varied carbohydrate compositions possess a plenty of beneficial properties. Different probiotic microbes have unique behavior in expressing their capability to display significant health promoting characteristics in the form of polysaccharides. In this new era of alternative medicines, these polysaccharides are considered as substitutes for synthetic drugs. The EPS finds applications in various fields like textiles, cosmetics, bioremediation, food and therapeutics. The present review is focused on sources, chemical composition, biosynthetic pathways of EPS and their biological potential. More attention has been given to the scientific investigations on antimicrobial, antitumor, anti-biofilm, antiviral, anti-inflammatory and immunomodulatory activities.

Keywords: Biosynthetic pathway; Exopolysaccharides; Health potential; Lactic acid bacteria; Probiotics; Structure.

Fig. 1

Different sources of probiotic bacteria.

Fig. 2

Classification of bacterial exopolysaccharides.

Fig. 3

Biosynthetic pathway of EPS.

Fig. 4

Biological activities of EPS.

Fig. 5

In-vitro anti-inflammatory activity of EPS from LAB on LPS stimulated RAW 264.7 macrophages. EPS binds to TLR-4 on macrophage cell surface and activates the cell through NF-κB and MAPK pathways. It has been observed that EPS treatment down regulates the NF-κB activation by inhibiting the phosphorylation of NF-κB inhibitor (Iκ-B). Consequently the level of pro inflammatory mediators decreases and anti-inflammatory mediators increases in the cell. Activation of MAPK pathway results in enhanced proliferation of macrophages. The expression of relevant mRNAs and proteins were confirmed by qRT-PCR and western blotting.