Reversible extension and shrinkage of solvent-responsive dextran chains produced by enzymatic reaction

Dextransucrase produces dextran and fructose from sucrose as a substrate, and dextran forms a complex with dextransucrase at the active site. Dextran chains were formed on the surface of an inorganic porous membrane, Shirasu Porous Glass membrane, via the enzymatic reaction. Dextran-containing membrane was prepared by permeating dextransucrase solution and then sucrose solution. Pure water was passed through the dextran-containing membrane to measure the pressure loss, from which the membrane porosity was determined using the Kozeny–Carman equation. Production of dextran chains in the porous membrane reduced the membrane porosity by more than 50%. When water–methanol solutions were permeated through the dextran-containing membrane, the porosity of membrane increased with proportion of methanol, indicating shrinkage of dextran immobilized on the surface of membrane. When water and 50% (v/v) methanol solutions were alternately passed though the membrane, high and low pressures were reproducibly determined by permeation of water and methanol solution, respectively. Dextran chains produced by the enzymatic reaction thus showed reversible extension and shrinkage in water and methanol–water solution