Fermentation properties of low-quality red alga Susabinori Porphyra yezoensis by intestinal bacteria.

Susabinori (Porphyra yezoensis), a red alga, is cultured and processed into a sheet-style dried food, nori, in Japan. But significant amounts of cultured susabinori, which has a low protein content is discarded because of its low quality. The protein content of nori has been reported to be correlated inversely with the carbohydrate content. In this study, we examined the relationship between the protein content and the fermentation of nori by means of bfidobacteria. nori with a low protein content (25% on dry base) was strongly fermented by bifidobacteria, whereas nori with a high protein content (41% on dry base) was not. nori with a low protein content contained large amounts of glycerol galactoside (GG, floridoside: 2-O-glycerol-alpha-D-galactoside, isofloridoside: 1-O-glycerol-alpha-D-galactoside), more than 10% w/w in the dried condition, and GG was the main substrate for fermentation by bifidobacteria. GG was not digested by digestive enzymes, and was not absorbed in the small intestine. These results suggest that GG can be used as a substrate for fermentation by bifidobacteria, and possibility of GG as a prebiotic.

Inhibitory effect of porphyran, prepared from dried "Nori", on contact hypersensitivity in mice.

Porphyran is a major component of the red algae, Porphyra tenera and P. yezoensis, which are processed into a sheet type of dried food, "Nori". Porphyran has been reported to activate murine macrophages by in vitro and i.p. injection studies. The contact hypersensitivity (CHS) reaction in mice is commonly used as a model to evaluate the anti-allergic activity of food and food components. We therefore studied the effect of porphyran on the CHS reaction in Balb/c mice to evaluate anti-allergic activity of porphyran. We found that an oral administration of porphyran (2% in drinking water) suppressed the CHS reaction (ear edema) induced by 2,4,6-trinitrochlorobenzene. We also found that porphyran suppressed the serum level of IgE and the production of interferon-gamma (IFN-gamma) in the challenged ear lobe. We conclude from these results that the CHS reaction was suppressed by oral porphyran due to the decreased serum level of IgE and the production of IFN-gamma in the challenged ear lobe.