Abstract
Thallus of the marine red alga Pyropia yezoensis is receiving
increased attention as an industrially and economically important species
for production of not only the Japanese traditional food, nori, but also
high-quality agar polysaccharides. We have already demonstrated that the
yield of agar from discolored thalli is higher than that from normal ones;
however, the cause of this characteristic is still unclear. To address a
reason why discolored P. yezoensis is suitable for agar
production, we here compared a stainability between normal and discolored
thalli with toluidine blue, which is a basic dye causing metachromasy for
acidic polysaccharides, because cell wall of this species contains the
sulfated acidic porphyran as a precursor of agar. As results, although
porphyran in the cell wall of both materials was dyed in purplish red by
metachromasy, intensity and area of staining were considerably higher and
wider in discolored thalli. In addition, cells of discolored thalli were
severely damaged and destroyed during the process of agar extraction.
These findings indicate that both substantial amount and efficient
extraction of porphyran are responsible for high yield of agar from
discolored P. yezoensis thalli.
