STRUCTURE AND PROPERTIES OF AGAR FROM 2 UNEXPLOITED AGAROPHYTES FROM VENEZUELA

The red seaweeds Gelidiella acerosa and Gracilaria mammillaris growing along the coast of Venezuela were investigated as potential economic sources of agar. Agar extracted from Gracilaria mammillaris accounted for 27% of the algal dry weight but had quite a poor gelling ability b ecause of the presence of alkali-stable sulphate groups on the D-galac tose residue. However, the gel strength of its aqueous solutions was c onsiderably enhanced by the addition of potassium, sodium and calcium ions (up to 1N). On the contrary, the galactan from Gelidiella acerosa (yield of about 20% w/w) exhibited quite good properties. In particul ar, the gel strength was comparable to that of commercial agaroses. Su lphate esters were not detectable by chemical methods and NMR spectros copy revealed an agarose backbone with a high degree of methylation on both D and L-galactose residues.