Effect of cell culture medium pH on rare sugar production and enhanced bioactive polysaccharide capacity from Arachis pintoi-associated bacteria

Abstract

The health benefits of rare sugars as substitute sweeteners and their enormous commercial potential across various industries have attracted significant attention. However, their low availability and the limited, costly synthesis methods remain major obstacles to their widespread use. Bacterial exopolysaccharides (EPSs), composed of diverse monosaccharides, offer a sustainable source of rare sugars. In this study, exopolysaccharide—producing bacteria were isolated from the rhizosphere of the leguminous plant Arachis pintoi. Two highly productive strains R3 and R11, produced 5.80 g/L and 6.07 g/L of EPS, respectively. Gas Chromatography–Mass Spectrometry (GC–MS) analysis revealed that rhamnose and glucosamine were the predominant sugar monomers in the EPSs produced by these bacteria. Additionally, other rare sugars, including fucose and arabinose in lower concentrations, were also identified. Besides, alkali media modified the monosaccharide profile of the EPS and substantially increased its production, with yields increasing by 101.07% in R3 and 238.89% in R11. Particularly, when the pH increased, EPS from R11 showed an enhancement in ribose, galacturonic acid, and glucosamine synthesis. According to the analysis of 16S rRNA and phylogenetic tree, the promising EPS producers R3 and R11 were identified as Enterobacter sp. and Klebsiella sp. The EPSs produced by these bacteria demonstrated notable antioxidant capacity. The findings of this study indicate that exopolysaccharides (EPSs) have potential as raw materials for the production of rare sugars applicable in the food, nutraceutical, and pharmaceutical industries. Furthermore, the results underscore the effectiveness of alkaline media in enhancing the yield of EPSs. This finding paves the way for a novel research avenue focused on the production of rare sugars for industrial applications using exopolysaccharides (EPSs) synthesized by Enterobacter sp. and Klebsiella sp.

Keywords

Antioxidant activities / Exopolysaccharides (EPS) / Rare sugars / Rhizosphere

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Funding

Viet Nam National University Ho Chi Minh City(C2023-16-15)

RIGHTS & PERMISSIONS

Jiangnan University