Structural Features of Enzymatic Hydrolysate of Porphyran Isolated from Porphyra yezoensis

Abstract

Enzymatic hydrolysate of porphyran from Porphyra yezoensis was prepared by treatment with ß-agarase. The hydrolysate was fractioned into molecular sizes of <3, 3-30, and 30-300 kDa using an ultrafiltration membrane. The membrane fractions were further separated into neutral and anionic fractions using Dowex 1 8 ion exchange chromatography. After hydrolysis of porphyran with ß-agarase, 23.2% of the starting porphyran was recovered as a neutral fraction of low-molecular weight (<3 kDa), and 28.9% remained as an enzyme-resistant anionic fraction of high molecular weight (>300 kDa). Desulfation of porphyran and 13 C-NMR analysis of the anionic fraction of low molecular weight (<3 kDa) showed that the anionic fraction has a backbone consisting of 3-linked ß-D-galactose units alternating with either 4-linked a-L-galactose 6-sulfate or 3, 6-anhydro-a-L-galactose units. These results indicate that porphryan is a copolymer of two moieties, about 25% of which are composed of neoagarose moieties and 75% as anionic moieties.