Combined Acid and Enzymatic Hydrolysis Using an Endolytic κ-Carrageenase RsKC16A for Efficient Preparation of Carrageenanoligosaccharides.

κ-Carrageenases play a crucial role in the high-value utilization of carrageenan polysaccharides. This study characterized an endolytic κ-carrageenase, RsKC16A, and identified its main products as κ-neocarratetrose, κ-neocarrahexaose, κ-neocarraoctaose, and κ-neocarradecaose. A mixture of carrageenanoligosaccharides, consisting mainly of G4S, κ-carrabiose, κ-carratriose, κ-carrapentaose, κ-carraheptaose, κ-carranonaose, κ-carraundecaose, and κ-carrauntetradecaose, was prepared through acidolysis of κ-carrageenan. Further exploration of RsKC16A revealed that it primarily cleaves the pentasaccharide unit from the nonreducing end of κ-carraheptaose, κ-carranonaose, κ-carraundecaose, and κ-carrauntetradecaose. The oligosaccharides prepared by combining acid hydrolysis and enzymes are composed of κ-carratriose, κ-carrapentaose, and κ-carranonaose, with pentasaccharides being the most abundant component. 0.312 g of κ-carrapentaose was prepared from 3 g of κ-carrageenan. Additionally, the results demonstrated that relatively pure κ-carratriose can be produced using κ-neocarrabiose- or κ-neocarratetrose-producing κ-carrageenases. This study presents new methods for the efficient preparation of odd-numbered carrageenanoligosaccharides and expands the range of oligosaccharides that can be produced by κ-carrageenases.