Production and physicochemical characterization of exopolysaccharides from the salt-tolerant actinobacterial strain Zhihengliuella halotolerans DT-Z1

Extremophiles often produce exopolysaccharides (EPSs) as a strategy in harsh environments, thus attracting significant interest for their properties and applications. A salt-tolerant EPS-producing <i>Zhihengliuella halotolerans</i> DT-Z1 was acquired and its EPS yield was optimized using response surface methodology, significantly increased from 2.86 to 10.26 g/L. Two fractions (EPS1-0 and EPS1-1) were purified by ethanol precipitation and anion exchange and gel filtration chromatography. Structural characteristics confirmed that both EPS1-0 and EPS1-1 are linear β-(2-6)-linked fructans with high molecular weights of 7.55 × 10⁷ and 7.54 × 10⁷ g/mol, respectively. Bioassays demonstrated that pre-treatment of wheat seeds with these EPS wheat seeds under saline-alkali conditions increased germination rates by 3.3%-19.8%, root length by 12.3%-14.8%, and shoot length by 12.7%-38.9%. These findings indicate that the levan-type fructans from <i>Z. halotolerans</i> DT-Z1 are promising functional biopolymers for potential applications in agriculture, particularly in the development of saline-alkali lands.