**2. Composition of** *Lactobacillus* **exopolysaccharide (EPS)**

The bioproduction of exopolysaccharides is of universal occurrence among eukaryotic (plants, seaweeds) and prokaryotic (bacteria) organisms. Microbial exopolysaccharides have many uses in numerous fields including food industries, farming, textiles, cosmetics, bioremediation and therapeutics, and pharmacy because of their different composition, structure, physical and chemical properties [5, 6].

Based on the type of monosaccharide monomers, EPS are divided into two groups of homopolysaccharides and heteropolysaccharides. The *Lactobacillus* spp. like other LAB can synthesize homopolysaccharides or heteropolysaccharides. The synthesized homopolysaccharides are glucans or fructans, which are composed of only one type of monosaccharide (glucose or fructose, respectively), whereas the heteropolysaccharides contain different types of monosaccharides in different proportions [7].

The homopolysaccharides EPS of lactobacilli with a molecular weight of greater than 106 Dalton are either branched or unbranched and composed of either glucose or fructose and are categorized into α-D-glucans (Dextran, Mutan, Alternan, and Reuteran), β-D-glucans, fructans (Levan and Inulin) and polygalactans [6, 8, 9]. Similarly, heteropolysaccharides EPS of lactobacilli have a molecular weight ranging from 104 and 6.0 × 106 Dalton and are made up of common sugars (D-glucose, D-galactose), rare sugars (L-rhamnose, mannose, arabinose, xylose, fucose, N-acetylglucosamine, N-acetylgalactosamine or glucuronic acid) and non-carbohydrate components (acetate, phosphate, sulfate, pyruvate, propionate, glycerate, amino acid, L- glutamate, and succinate [6, 9, 10]. Some examples of heteropolysaccharides EPS of lactobacilli are gellan, xanthan, and kefiran [6].
