Preparation of κ-carra-Oligosaccharides with Microwave Assisted Acid Hydrolysis Method

A rapid method of microwave assisted acid hydrolysis was established to prepare κ-carra-oligosaccharides. The optimal hydrolysis condition was determined by an orthogonal test. The degree of polymerization(DP) of oligosaccharides was detected by high performance thin layer chromatography(HPTLC) and polyacrylamide gel electrophoresis(PAGE). Considering the results of HPTLC and PAGE, the optimum condition of microwave assisted acid hydrolysis was determined. The concentration of κ-carrageenan was 5 mg m L-1; the reaction solution was adjusted to p H 3 with diluted hydrochloric acid; the solution was hydrolyzed under microwave irradiation at 100 for 15℃ min. Oligosaccharides were separated by a Superdex 30 column(2.6 cm × 90 cm) using AKTA Purifier UPC100 and detected with an online refractive index detector. Each fraction was characterized by electrospray ionization mass spectrometry(ESI-MS). The data showed that odd-numbered κ-carra-oligosaccharides with DP ranging from 3 to 21 could be obtained with this method, and the structures of the oligosaccharides were consistent with those obtained by traditional mild acid hydrolysis. The new method was more convenient, efficient and environment-friendly than traditional mild acid hydrolysis. Our results provided a useful reference for the preparation of oligosaccharides from other polysaccharides.