Physicochemical and Structural Characterization of Alkali-Treated WL Gum from Marine sp. WG

Sphingan WL gum (WL), a kind of exopolysac-charide, is produced by Sphingomonas sp. WG, which was screened from sea mud samples of Jiaozhou Bay by our group. The solubility of WL was investigated in this work. First, 1 mg/mL of WL solution was stirred at room temperature for at least 2 h to obtain a uniform opaque liquid, and further the solution became clear with the increased NaOH and stirring time. Subsequently, the structural features, solubility, and rheological properties of WL before and after alkali treatment were compared systematically. FTIR, NMR, and zeta potential results indicate that the alkali causes acetyl group hydrolysis and carboxyl group deprotonation. XRD, DLS, GPC, and AFM results suggest that the alkali destroys the ordered arrangement and inter-and intrachain entanglement of polysaccharide chains. In the same case, 0.9 M NaOH-treated WL presents better solubility (stirring for 15 min to obtain a clarified solution) but, unsurprisingly, worsens rheological properties. All results demonstrated that the good solubility and transparency of alkali-treated WL will help promote its postmodification and application.

Automated summary

The solubility of Sphingan WL gum (WL) was investigated in this study. Alkali treatment was found to improve the solubility of WL but also worsen its rheological properties. The alkali caused hydrolysis and deprotonation of acetyl and carboxyl groups, and destroyed the ordered arrangement and entanglement of polysaccharide chains. The results suggest that the alkali-treated WL could be more suitable for postmodification and application.