Abstract:D--allulose is a C-3 epimer of D--fructose. It has similar sweetness to sucrose but provids significantly lower calorie, which makes it a functional sweetener with important application potentials. The enzymatic preparation of D--allulose from D--fructose catalyzed by D--psicose 3-epimerase (EC 5.1.3.30, DPEase) has attracted much attention owing to its simple purification process and high product concentration. To obtain higher expression of enzyme, DPEase was produced by a previously constructed strain, <>Biacillus subtilis 1A751/pUB-P43dpe-dal, in a 3 L fermentor. By optimizing the dissolved oxygen (DO), pH, temperature and initial carbon source concentration, the optimal fermentation conditions were determined as follows: DO 30%, pH 6.0, 37 ℃, initial glucose concentration of 15 g/L. And the maximum enzyme activity reached 78.3 U/mL. On this basis, the fed-batch fermentation was applied, and the optimal fed fermentation time was 5 h. At a constant feeding rate of 8.0 g/（L·h）, the whole-cell enzyme activity reached 123.0 U/mL after 9 h fermentation. This strategy of fermentation could provide a theoretical basis for the expanding the industrial production of D--allulose.
