Very high molar mass dextrans

1. A process for producing dextrans having a weight-average molar mass M w , at least equal to 0.7×10 9 g.mol −1 , and a dispersity index D i of between 1.3 and 3, wherein α-1,6 glucosidic bonds in the dextrans comprise between 95% and 99% of glucosidic bonds, the process comprising reacting sucrose with a dextransucrase that comprises a protein which is a function-preserving dextransucrase variant of the amino acid sequence set forth in SEQ ID NO:1, said protein having at least 98% amino acid sequence identity with the amino acid sequence set forth in SEQ ID NO: 1, wherein the amino acid sequence of the protein comprises:

(a) a glycoside hydrolase family 70 (GH70) DED catalytic triad,

(b) a glycoside hydrolase family 70 conserved catalytic core protein motif I corresponding to amino acids 936-942 of SEQ ID NO:1,

(c) a glycoside hydrolase family 70 conserved catalytic core protein motif II corresponding to amino acids 458-468 of SEQ ID NO:1,

(d) a glycoside hydrolase family 70 conserved catalytic core protein motif III corresponding to amino acids 495-505 of SEQ ID NO:1, and

(e) a glycoside hydrolase family 70 conserved catalytic core protein motif IV corresponding to amino acids 568-582 of SEQ ID NO:1.

2. The process of claim 1 , wherein the step of reacting is carried out at a temperature of between 20° C. and 40° C.

3. The process of claim 1 , wherein the sucrose is present at a concentration that is between approximately 50 and 200 g.l −1 .

4. The process of claim 1 , wherein pH during the step of reacting is between approximately 5 and 6.5.

5. The process of claim 1 wherein the dextransucrase is

a dextransucrase comprising the amino acid sequence set forth in SEQ ID NO: 1.

6. The process of claim 1 wherein wherein α-1,6glucosidic bonds in the dextrans comprise between 97% and 98% of glucosidic bonds.