Ulvan as a source of oligosaccharides for biological applications: enzymatic hydrolysis in a biocompatible medium

Ulvan oligosaccharides, which exhibit greater solubility than high molecular weight ulvan, hold significant potential for the valorization of Ulva biomass. They have been shown to promote the growth of probiotic bacteria in fermentation models and have demonstrated protective and anti-inflammatory effects in animal models. The enzymatic hydrolysis of ulvan using the commercial ulvan lyase PLSV_3875 bypasses the challenge posed by the resistance of ulvanobiuronic acids to conventional acidic hydrolysis. This study aimed to develop a rapid, scalable, and efficient method for a complete ulvan hydrolysis under reduced salt concentrations, yielding oligosaccharides suitable for biological applications. The enzyme's robustness and kinetic parameters were evaluated. Enzyme activity was assessed at pH 6-10.5 with 0-100 mM Tris-HCl, carbonate or phosphate buffer, and 0-200 mM NaCl/KCl. Optimal conditions were identified as 3 mg/mL ulvan, 25 mM KCl, and 100 mM phosphate buffer at pH 7.5. The resulting oligosaccharides were characterized using 2D-NMR and UHPLC-MS/MS.