Composition and distribution of carrabiose moieties in hybrid kappa-/iota-carrageenans using carrageenases

Hybrid kappa/l-carrageeans extracted from Gigartina skottsbergii, Chondracanthus chamissoi, and Chondrus crispus were incubated with Pseudoalteromonas carrageenovora kappa-carrageenase and Alteromonas fortis l-carrageenase. The degradation products as well as the resistant fraction were fully characterized by chromatography, NMR, and mass spectrometry. The low percentage of degradation observed after treatment by the l-carrageenase suggests that long segments of l-carrabiose or block of l-carrageenan are low in abundance. The degradation products of the kappa-carrageenase allow discriminating three modes Of kappa-carrabiose distribution: blocks Of kappa-carrabiose, kappa-carrabiose rich fraction containing l-carrabiose units probably randomly distributed, and l-carrabiose rich fraction which corresponds to the resistant fraction. The proportions of each fraction were related to the botanical origin as well as the place of growth of the seaweed.