Exopolysaccharide Produced by Leuconostoc sp. LU1 Using Sweet Potato (Ipomoea batatas) Waste: Physicochemical and Functional Characterization

Exopolysaccharides (EPS) are polymers of high industrial value due to their wide range of uses, and their profitable and sustainable production is a constant challenge. The objective of this work was to conduct EPS production by Leuconostoc sp. LU1 using sweet potato (Ipomoea batatas) waste as a substrate, as well as its physicochemical and functional characterization. Leuconostoc sp. LU1, isolated from the gherkin fruit, was phenotypically characterized and phylogenetically analyzed. The effect of different pH levels, yeast extract, and sweet potato waste on biomass and EPS production was evaluated by simple factor analysis. The physicochemical characterization was performed using FTIR, TGA, NMR and HPLC techniques, while the functional properties determined were the water solubility index, water and oil retention capacity, and antioxidant capacity. Regarding the evaluated parameters, cultivation at pH 5, with 1.0 g L^− 1 yeast extract and 100% (v/v) sweet potato residue, resulted in a production of 5.86 ± 0.04 g L^− 1 of EPS with a yield of 0.49 g g^− 1 and a productivity of 0.06 g L^− 1 h^− 1. Analysis of the monosaccharide composition by HPLC indicated that the EPS corresponds to a homopolymer composed of glucose units; in addition, it showed a degradation temperature of 205 °C. NMR spectroscopy indicated anomeric proton signals corresponding to α-glucopyranosid, consistent with the structure of dextran. Likewise, the biopolymer exhibited high water solubility and a water retention capacity of 127.60 ± 0.41% (w/w). Additionally, the EPS presented an ABTS•+ free radical scavenging capacity of 92 ± 0.03%. The study highlights the production of an exopolysaccharide by a native strain, which promotes the development of a sustainable and profitable bioprocess by taking advantage of agroindustrial waste.