A novel two-step enzymatic synthesis of blastose, a β-d-fructofuranosyl-(2↔6)-d-glucopyranose sucrose analogue

Abstract

Blastose, a natural disaccharide found in honey, is usually found as a byproduct of fructo-oligosaccharide synthesis from sucrose with fructosyltransferases. In this study, we describe a novel two-step biosynthetic route to obtain blastose, designed from a detailed observation of B. subtilis levansucrase (SacB) acceptor structural requirements for fructosylation. The strategy consisted first in the synthesis of the trisaccharide O-β-d-Fruf-(2↔6)-O-α-d-Glcp-(1↔1)-α-d-Glcp, through a regioselective β-d-transfructosylation of trehalose (Tre) which acts as acceptor in a reaction catalyzed by SacB using sucrose or levan as fructosyl donor. In this reaction, levansucrase (LS) transfers regioselectively a fructosyl residue to either C₆-OH group of the glucose residues in Tre. The resulting trisaccharide obtained in 23% molar yield based on trehalose, was purified and fully characterized by extensive NMR studies. In the second step, the trisaccharide is specifically hydrolyzed by trehalase, to obtain blastose in 43.2% molar yield based on the trisaccharide. This is the first report describing the formation of blastose through a sequential transfuctosylation-hydrolysis reaction.

Keywords: Blastose; Erlose (PubChem CID: 193471); Lactosucrose (PubChem CID: 174626); Levan (PubChem CID: 440946); Levanobiose (PubChem CID: 439555); Levansucrase; Neokestose (PubChem CID: 107452); Prebiotics; Regioselectivity; Sucrose (PubChem CID: 5988); Trehalase; Trehalose; Trehalose (PubChem CID: 7427); d-Fructose (PubChem CID: 5984); d-Galactose (PubChem CID: 6036); d-Glucose (PubChem CID:5793); dl-Xylose (PubChem CID: 644160).