Work

Production and functional characterization of an extracellular galactoglucan G2 secreted by the Sinorhizobium sp. ACT002

Year: 2025

Type: article

Abstract: Galactoglucans exhibit diverse properties, yet their broad application is limited by production challenges. Herein, we isolated a high-polysaccharide-producing strain, Sinorhizobium sp. ACT002. In shake flasks, ACT002 achieved a productivity of 4.21 ± 0.16 g/L/d, surpassing reported values for Rhizobium / Sinorhizobium species. The purified polysaccharide, G2, had a weight-average molecular weight of 2.23 × 10 6 Da and displayed a smooth surface as observed by SEM. Structural analyses, including FT-IR, methylation-GC/MS, and 1D/2D NMR, identified G2 as a linear galactoglucan composed of the disaccharide repeating unit →3)-β-D-Glc p -(1→3)-(4,6-Pyr)-α-D-Gal p -(1→, closely resembling the EPS II produced by S. meliloti . The 4,6-positions of galactosides were substituted with equimolar pyruvyl groups, while its acetyl group content was lower than that of EPS II. Rheological characterization revealed a critical concentration of 3.23 g/L for pseudoplastic behavior. Among various salts, KCl exerted more pronounced effects on the Carreau-Yasuda flow properties, viscoelasticity, and thermal stability of G2. Moreover, G2 possessed moisture absorption/retention capacities comparable to hyaluronan. It also exhibited notable antioxidant activity, UV absorption, and minimal hemolytic effects. Topical application of G2 effectively mitigated UV-B-induced skin damage in mice, promoting restoration of epidermal integrity and tissue organization. These findings highlight the potential application of G2 in rheology modification, moisture retention, and UV protection.

Source: Carbohydrate Polymers

DOI: 10.1016/j.carbpol.2025.124718