Identification and characterisation of dextran produced by a novel high yielding Weissella cibaria Fiplydextran...

An exopolysaccharide (EPS)-producing bacterial strain was isolated from fermented soy milk and identified as Weissella cibaria strain Fiplydextran through morphological, biochemical and 16S rDNA sequence analysis. Here, we report the optimisation of cultural conditions for the organism to achieve maximum EPS production, along with its molecular characterisation, functional properties, and prebiotic potential. The exceptionally high EPS yield (0.61 g per g of sucrose) was obtained from the optimised medium (200 g/L of sucrose, 15 g/L of yeast extract) at 30 °C after 48 h. HPAEC-PAD analysis revealed that the EPS is homopolymer of glucose having M_w as 3.23 × 10⁷ Da determined using viscosity method. Methylation analysis and NMR results confirmed the EPS as dextran with α (1 → 6)-linkage (96.5 %) as main chain and α (1 → 3)- as branch chain linkage (3.5 %). Thermogravimetric analysis exhibited higher thermal stability of EPS. The EPS was observed to support the growth of Bacteroides spp. in pure culture form but not that of Lactobacillus or Bifidobacterium spp. However, a low level of bifidogenic activity was observed upon use of mixed culture of B. fragilis and B. longum. The research implies industrial applications of W. cibaria Fiplydextran for the production of high molecular weight dextran with better yield.