FIELD OF INVENTION

The present disclosure is in the field of poly alpha-1,3-glucan derivatives. For example, the disclosure pertains to poly alpha-1,3-glucan esters and methods of their preparation using cyclic organic acid anhydrides.

BACKGROUND

Driven by a desire to find new structural polysaccharides using enzymatic syntheses or genetic engineering of microorganisms or plant hosts, researchers have discovered polysaccharides that are biodegradable, and that can be made economically from renewable resource-based feedstocks. One such polysaccharide is poly alpha-1,3-glucan, a glucan polymer characterized by having alpha-1,3-glycosidic linkages. This polymer has been isolated by contacting an aqueous solution of sucrose with a glucosyltransferase enzyme isolated fromStreptococcus salivarius(Simpson et al.,Microbiology141:1451-1460, 1995). Films prepared from poly alpha-1,3-glucan tolerate temperatures up to 150° C. and provide an advantage over polymers obtained from beta-1,4-linked polysaccharides (Ogawa et al.,Fiber Differentiation Methods47:353-362, 1980).

U.S. Pat. No. 7,000,000 disclosed the preparation of a polysaccharide fiber comprising hexose units, wherein at least 50% of the hexose units within the polymer were linked via alpha-1,3-glycosidic linkages using anS. salivariusgtfJ enzyme. This enzyme utilizes sucrose as a substrate in a polymerization reaction producing poly alpha-1,3-glucan and fructose as end-products (Simpson et al., 1995). The disclosed polymer formed a liquid crystalline solution when it was dissolved above a critical concentration in a solvent or in a mixture comprising a solvent. From this solution, continuous, strong, cotton-like fibers, highly suitable for use in textiles, were spun and used.

Yui et al. (Int. J. Biol. Macromol.14:87-96, 1992) disclose using poly alpha-1,3-glucan extracted from the fruiting body of the fungus,Laetiporus silphureus, to synthesize poly alpha-1,3-glucan triacetate. The structure of this polymer was analyzed by X-ray crystallography.

Ogawa et al. (Carb. Poly.3:287-297, 1983) used three different samples of poly alpha-1,3-glucan to prepare poly alpha-1,3-glucan triacetate. One sample was isolated from a bacterial extracellular polysaccharide, and the other two samples were extracted from fruiting bodies of fungi. The structures of these polymers were analyzed by X-ray crystallography.

U.S. Patent Appl. Publ. Nos. 2014/0187767 and 2014/0187766 disclose poly alpha-1,3-glucan esters and methods of their production, as well as films comprising such poly alpha-1,3-glucan esters.

Development of new poly alpha-1,3-glucan ester derivatives and methods of preparing such derivatives is desirable given their potential utility in various applications.

SUMMARY OF INVENTION

One embodiment of the present disclosure concerns a composition comprising a poly alpha-1,3-glucan ester compound represented by the structure:


wherein
(i) n is at least 6;
(ii) each R is independently an —H or a first group comprising —CO—Cx—COOH, wherein the —Cx— portion of the first group comprises a chain of 2 to 6 carbon atoms; and
(iii) the compound has a degree of substitution with the first group of about 0.001 to about 3.0.

In another embodiment, the —Cx— portion of the first group comprises only CH2groups. The first group in this embodiment can comprise —CO—CH2—CH2—COOH, —CO—CH2—CH2—CH2—COOH, —CO—CH2—CH2—CH2—CH2—COOH, —CO—CH2—CH2—CH2—CH2—CH2—COOH, or —CO—CH2—CH2—CH2—CH2—CH2—CH2—COOH, for example.

In another embodiment, the —Cx— portion of the first group comprises: (i) at least one double-bond in the carbon atom chain, and/or (ii) at least one branch comprising an organic group.

In another embodiment, the —Cx— portion of the first group comprises at least one double-bond in the carbon atom chain. The first group comprises —CO—CH═CH—COOH in another embodiment.

In another embodiment, the —Cx— portion of the first group comprises at least one branch comprising an organic group. The first group comprises:


in another embodiment.

In another embodiment, the present disclosure concerns a method of producing a poly alpha-1,3-glucan ester compound. This method comprises:

(a) contacting poly alpha-1,3-glucan in a reaction with a cyclic organic anhydride, thereby producing a poly alpha-1,3-glucan ester compound represented by the structure:


wherein(i) n is at least 6;(ii) each R is independently an —H or a first group comprising —CO—Cx—COOH, wherein the —Cx— portion of said first group comprises a chain of 2 to 6 carbon atoms; and(iii) the compound has a degree of substitution with the first group of about 0.001 to about 3.0; and

(b) optionally, isolating the poly alpha-1,3-glucan ester compound produced in step (a).

In another embodiment, the reaction initially consists of the poly alpha-1,3-glucan and cyclic organic anhydride, wherein the cyclic organic anhydride is melted.

In another embodiment, the reaction does not comprise an organic solvent.

In another embodiment, the reaction comprises aqueous conditions. A basic pH is maintained during the reaction in another embodiment.

In another embodiment, the poly alpha-1,3-glucan and poly alpha-1,3-glucan ester are each in a solid form during the reaction.

In another embodiment, the reaction does not comprise a catalyst.

