Expanding the application range of the κ‑carrageenase OUC-FaKC16A when preparing oligosaccharides from κ-carrageenan and furcellaran.

Carrageenan oligosaccharides are important products that have demonstrated numerous bioactivities useful in the food, medicine, and cosmetics industries. However, the specific structure-function relationships of carrageenan oligosaccharides are not clearly described due to the deficiency of high specific carrageenases. Here, a truncated mutant OUC-FaKC16Q based on the reported κ-neocarratetrose (Nκ4)-producing κ-carrageenase OUC-FaKC16A from Flavobacterium algicola was constructed and further studied. After truncating the C-terminal Por_Secre_tail (PorS) domain (responsible for substrate binding), the catalytic efficiency and temperature stability decreased to a certain extent. Surprisingly, this truncation also enabled OUC-FaKC16Q to hydrolyze Nκ4 into κ-neocarrabiose (Nκ2). The offset of Arg₂₆₅ residue in OUC-FaKC16Q may explain this change. Moreover, the high catalytic abilities, the main products, and the degradation modes of OUC-FaKC16A and OUC-FaKC16Q toward furcellaran were also demonstrated. Data suggested OUC-FaKC16A and OUC-FaKC16Q could hydrolyze furcellaran to produce mainly the desulfated oligosaccharides DA-G-(DA-G4S)₂ and DA-G-DA-G4S, respectively. As a result, the spectrum of products of κ-carrageenase OUC-FaKC16A has been fully expanded in this study, indicating its promising potential for application in the biomanufacturing of carrageenan oligosaccharides with specific structures.

Supplementary information: The online version contains supplementary material available at 10.1007/s42995-023-00181-2.