Functional Characterisation and Application of Exopolysaccharides Produced by Lactic Acid Bacteria Isolated from Nigerian Traditional Fermented Dairy Products

Exopolysaccharides produced by lactic acid bacteria are high-molecular-weight biopolymers with demonstrated functional properties relevant to food texture modification, prebiotic activity, and preservation. While commercial exopolysaccharide-producing strains are well characterised, those derived from traditional African fermented dairy products represent an unexplored source of novel functional biopolymers adapted to sub-Saharan African ecological conditions. This study conducted the functional characterisation and food application assessment of exopolysaccharides produced by lactic acid bacteria isolated from nono (fermented Fulani milk) and wara (fresh acid-coagulated cheese) produced in Plateau and Kwara states of Nigeria. Forty-three exopolysaccharide-producing lactic acid bacteria strains were isolated, identified by 16S rRNA gene sequencing, and screened for exopolysaccharide yield and composition. Selected high-yield strains were characterised for exopolysaccharide molecular weight by size exclusion chromatography with multi-angle light scattering, sugar composition by gas chromatography after methanolysis, and structural linkage by nuclear magnetic resonance spectroscopy. Functional properties assessed included water holding capacity, emulsification activity, antioxidant activity, and prebiotic index using in vitro batch fermentation. Application trials were conducted in yoghurt, soft cheese, and a cereal-based fermented porridge. Results identified novel heteropolysaccharides from three Lactobacillus plantarum strains with superior water holding capacity and prebiotic index values exceeding commercial standards. Yoghurt containing these strains showed improved texture, reduced syneresis, and extended shelf life. The study provides original characterisation data and applied food science evidence for indigenous exopolysaccharide exploitation. Keywords: exopolysaccharides, lactic acid bacteria, fermented dairy, functional properties, characterisation.