Enhancement of enzymatic synthesis of sucrose 6-acetate with Aspergillus oryzae fructosyltransferase using ionic liquid as a cosolvent

• Ionic liquid-containing buffer system was first applied in the enzymatic synthesis of sucrose 6-acetate.
• The [Dmim][PF6]–phosphate buffer system was identified as the optimum medium for the AoFT-catalyzed production of sucrose 6-acetate.
• The highest glucose 6-acetate conversion and sucrose 6-acetate yield in the [Dmim][PF6]–buffer system were 88.2% and 77.2%, respectively.

The aim of this study was to investigate the effects of using ionic liquids (ILs) as cosolvents on the enzymatic synthesis of sucrose 6-acetate (S6A) by Aspergillus oryzae fructosyltransferase (AoFT). Fifteen ILs were selected as IL-containing buffer systems to assist the catalytic reactions in the AoFT-catalyzed synthesis of S6A. An analysis of the catalytic efficiency and conformation of AoFT showed that the [Dmim][PF6]–phosphate buffer (20:80, v/v) system was the optimum medium for the AoFT-catalyzed production of S6A. The maximum glucose 6-acetate (G6A) conversion and S6A yield were obtained under the following conditions: reaction time 8 h, reaction temperature 55 °C, AoFT concentration 20 mg/mL, molar ratio of sucrose to G6A 4:1, and sucrose concentration 10 mg/mL. The reaction time decreased 0.33-fold, and the G6A conversion and S6A yield increased 2.90-fold and 3.18-fold, respectively, under these conditions. These results show that the use of ILs as cosolvents enhances the transfructosylation activity of AoFT in the enzymatic synthesis of S6A.

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