Dextran-poly alpha-1,3-glucan graft copolymers and synthesis methods thereof

1. A composition comprising a graft copolymer that comprises:

a backbone comprising dextran with a weight-average molecular weight (Mw) of at least about 10 million Daltons, and

(ii) poly alpha-1,3-glucan side chains comprising at least about 95% alpha-1,3-glucosidic linkages.

2. The composition of claim 1 , wherein the poly alpha-1,3-glucan side chains comprise at least about 99% alpha-1,3-glucosidic linkages.

3. The composition of claim 1 , wherein the individual Mw of one or more poly alpha-1,3-glucan side chains is at least about 100000 Daltons.

4. The composition of claim 1 , wherein the graft copolymer is insoluble under aqueous conditions.

5. The composition of claim 1 , wherein said dextran

is a product of a glucosyltransferase enzyme comprising an amino acid sequence that is at least 90% identical to SEQ ID NO:6 or SEQ ID NO:7, and wherein the Mw of said dextran is at least about 50 million Daltons.

6. The composition of claim 5 , wherein the Mw of said dextran is at least about 100 million Daltons.

7. The composition of claim 5 , wherein said dextran is a product of a glucosyltransferase enzyme comprising an amino acid sequence that is at least 95% identical to SEQ ID NO:6 or SEQ ID NO:7.

8. The composition of claim 5 , wherein the graft copolymer comprises at least about 2.0 wt % dextran.

9. The composition of claim 1 , wherein the composition is a product for aqueous liquid absorption selected from the group consisting of baby diapers, potty training pants, incontinence products, feminine hygiene products, wound healing dressings, and sanitary towels.

10. The composition of claim 1 , wherein the composition is a personal care product, household product, medical product, or industrial product.

11. An enzymatic reaction comprising (i) water, (ii) sucrose, (iii) dextran with a weight-average molecular weight (Mw) of at least about 10 million Daltons, and (iv) a glucosyltransferase enzyme that synthesizes poly alpha-1,3-glucan comprising at least about 95% alpha-1,3-glucosidic linkages,

wherein the enzymatic reaction produces a graft copolymer according to the composition of claim 1 .

12. The enzymatic reaction of claim 11 , wherein the initial concentration of said dextran in the reaction is at least about 2 g/L, and wherein the Mw of said dextran is at least about 50 million Daltons.

13. A method of preparing a graft copolymer, said method comprising:

(a) contacting at least (i) water, (ii) sucrose, (iii) dextran with a weight-average molecular weight (Mw) of at least about 10 million Daltons, and (iv) a glucosyltransferase enzyme that synthesizes poly alpha-1,3-glucan comprising at least about 95% alpha-1,3-glucosidic linkages,

whereby a graft copolymer according to the composition of claim 1 is produced; and

(b) optionally, isolating the graft copolymer produced in step (a).

14. The method of claim 13 , wherein the dextran entered into step (a) has an Mw of at least about 50 million Daltons and an initial concentration of at least about 2 g/L,

wherein the graft copolymer produced in step (a) is isolated, and wherein said isolation step comprises a filtration step, wherein the graft copolymer has a higher filtration rate compared to the filtration rate of a poly alpha-1,3-glucan homopolymer.

15. The composition of claim 7 , wherein said dextran is a product of a glucosyltransferase enzyme comprising an amino acid sequence that is at least 98% identical to SEQ ID NO:6 or SEQ ID NO:7.

16. The composition of claim 15 , wherein said dextran is a product of a glucosyltransferase enzyme comprising the amino acid sequence of SEQ ID NO:6 or SEQ ID NO:7.

17. The composition of claim 5 , wherein the Mw of said dextran is about 50-200 million Daltons.

18. The composition of claim 1 , wherein the dextran comprises at least 85% alpha-1,6 glucosidic linkages.

19. The composition of claim 8 , wherein the graft copolymer comprises at least 2.5 wt % dextran.