Very high molar mass dextrans

A process for producing dextrans having a weight-average molar mass Mw, at least equal to 0.7×109 g.mol−1, and a dispersity index Di 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.