Investigation on “spontaneous fermentation” and the productivity of microbial exopolysaccharides by Lactobacillus plantarum and Pediococcus pentosaceus isolated from wheat bran sourdough

Spontaneously fermented wheat bran sourdough (WBS) is a source of lactic acid bacteria (LAB) and metabolites with potential applications as functional ingredients. In this study, dominant LAB isolated from the spontaneous fermentation of WBS were analyzed for their exopolysaccharide (EPS) production capacities. Biochemical and molecular tests led to the identification of Lactobacillus plantarum and Pediococcus pentosaceus as the dominant isolates. Compositional analysis of microbial EPSs revealed the presence of 71.44 and 94.64% total carbohydrate content, 1.56 and 3.48% total protein content, and 0.23 and 0.49% w/w of phosphorus content for L. plantarum and P. pentosaceus, respectively. The molecular weight of EPS isolated from L. plantarum (5.36 × 105 Da) was greater than that of P. pentosaceus (4.65 × 105 Da). DPPH radical scavenging capacity, ABTS, and reducing power (FRAP) of the EPSs were significantly different (P < 0.05). FT-IR spectroscopy analysis demonstrated that the EPSs were complex polysaccharides containing different functional groups represented by stretching vibrations related to alcoholic, carboxylic acid and aromatic groups. In the context of their importance in sourdough fermentation, the EPSs demonstrated potential antioxidant properties.