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Abstract: Mild hydrolysis of Sphingomonas sp. ATCC 31555 polysaccharide WL-26 afforded a new oligosaccharide, F21. Structural resolution based on sugar and methylation analyses as well as NMR data revealed the oligosaccharide to have the following structure: Display Omitted [Copyright &y& Elsevier]

Biologically active gellan oligosaccharides (GOSs), newly found plant elicitors and biostimulants, are produced from the hydrolysis of gellan gum. Traditional hydrolysis with concentrated acid suffers from the problems of high pollution and low functional oligosaccharide yield because the process is difficult to control. Irradiation (60Co γ-ray) with a dosage ranging from 0 kGy to 175 kGy was used to degrade gellan gum efficiently and cleanly into low molecular weight (M w) gellan with an average M w ranging from 449,119 Da to 72,903 Da. The low M w gellan irradiated at 70 kGy was further hydrolyzed with low concentration acid (0.5 mol/L HCl) to produce GOSs with DPs mainly 4 and 8, indicating that the Rha-β-(1 → 3)-Glc bonds in gellan gum were easily cut to produce residues with tetrasaccharide repeat subunits. Besides antioxidant activity, GOSs were also proved with prebiotic activity by in vitro fecal fermentation in a self-designed bionic intestinal reactor. [Display omitted] • Gellan oligosaccharides were efficiently produced via coupled hydrolysis. • The structures of the hydrolysates (gellan oligosaccharides) were determined. • Specific gellan oligosaccharides (DPs 4 and 8) were isolated from the hydrolysates. • Gellan oligosaccharides were proved with prebiotic and antioxidant activities. • Biological activities of the specific oligosaccharides were compared. [ABSTRACT FROM AUTHOR]