Process for treating alginic acid to produce polyguluronic acids or concentrated solutions for use in producing polyguluronic acids

Abstract

A method of treating alginic acid to produce polyguluronic acids. The method involves: (a) mixing the alginic acid with water and lithium hydroxide in respective amounts sufficient to form a reaction mixture that is an acidic solution comprising at least 5 wt % of the alginic acid; (b) treating the reaction mixture, with addition of a periodic acid or a periodate salt, to effect an oxidation of the alginic acid that results in formation of (i) an oxidized product that, upon acidifying and heating, hydrolyzes into a plurality of components including polyguluronic acids that are substantially free of mannuronic acid contamination, with the polyguluronic acids having an average degree of polymerization of less than 20; and (ii) free iodine; (c) separating the free iodine from the reaction mixture; (d) acidifying and heating the reaction mixture to hydrolyze the oxidized product into the plurality of components; (e) adjusting the pH of the reaction mixture to form a precipitate of the polyguluronic acids; and (f) recovering the precipitate. There is also disclosed a method of treating alginic acid using steps (a), (b) and (c) to form concentrated solutions for use in producing polyguluronic acids.