Rational design improves both thermostability and activity of a new D-tagatose 3-epimerase from Kroppenstedtia eburnean to produce D-allulose

D-allulose is a naturally occurring rare sugar and beneficial to human health. However, the efficient biosynthesis of D-allulose remains a challenge. Here, we mined a new D-tagatose 3-epimerase from Kroppenstedtia eburnean (KeDt3e) with high catalytic efficiency. Initially, crucial factors contributing to the low conversion of KeDt3e were identified through crystal structure analysis, density functional theory calculations (DFT), and molecular dynamics (MD) simulations. Subsequently, based on the mechanism, combining restructuring the flexible region, proline substitution based onconsensus sequence analysis, introducing disulfide bonds, and grafting properties, and reshaping the active center, the optimal mutant M5 of KeDt3e was obtained with enhanced thermostability and activity. The optimal mutant M5 exhibited an enzyme activity of 130.8 U/mg, representing a 1.2-fold increase; Tm value increased from 52.7 °C to 71.2 °C; and half-life at 55 °C extended to 273.7 min, representing a 58.2-fold improvement, and the detailed mechanism of performance improvement was analyzed. Finally, by screening the ribosome-binding site (RBS) of the optimal mutant M5 recombinant bacterium (G01), the engineered strain G08 with higher expression levels was obtained. The engineered strain G08 catalyzed 500 g/L D-fructose to produce 172.4 g/L D-allulose, with a conversion of 34.4% in 0.5 h and productivity of 344.8 g/L/h on a 1 L scale. This study presents a promising approach for industrial-scale production of D-allulose. [Display omitted] •Identification of a ketose 3-epimerase derived from Kroppenstedtia eburnean (KeDt3e), capable of catalyzing the conversion of D-fructose to D-allulose.•Structural analysis and mechanistic insights into KeDt3e were conducted using molecular dynamics simulations, quantum chemical calculations, and density functional theory.•Implementation of various protein engineering strategies resulted in the creation of mutant variant M5 with improved thermostability and activity. Detailed mechanistic analysis was performed to understand the balance between thermal stability and activity.•Establishment of the optimal strain G08, in a 1 L reaction system, catalyzed the conversion of 500 g/L D-fructose with a 34.4% conversion rate at 0.5 h. This strain demonstrates potential for industrial-scale production.