1996 Volume 42 Issue 6 Pages 497-505
The vitamin B12 (B12) content in seven species of seaweed that are consumed frequently in Hokkaido, Japan, was microbiologically measured using Escherichia coil 215. Asakusanori (Porphyra tenera), maruba-amanori (Porphyra suborbiculata) and akaba-gin-nansou (Rhodogtossum pulcherum) showed higher B12 content than the other species, although the content varied greatly among samples in the same species. A bioautography on a thin-layer plate holding a mixture of silica gel and cellulose, differentiation of B12 and its analogues using a binding specificity of intrinsic factor and haptocorrin, and comparison of the B12 concentra tion determined by the radioisotope dilution assay method using the intrinsic factor as the B12-binding protein with that by the bioassay method, predominantly showed B12 in maruba-amanori and B12 analogues in wakame (Undaria pinnatifida) and akaba-gin-nansou. The B12 uptake of akaba-gin-nansou from artificial seawater was similar to that of asaku sanori that contained only B12.