D-Allulose 3-epimerase (DAEase) is the key enzyme catalyzing D-fructose to catalyze into D-allulose, a rare sugar in foods, which has lately drawn increasing worldwide attention owing to its possible health advantages and application as a substitute sucrose. This work focused on the development of an economical, scalable production method of DAEase by using the Escherichia coli BL21 star™ (DE3) as host expression. The research work aims to optimize the production of the enzyme through an auto-induction strategy in chemically defined media by using lactose as a natural inducer, thereby overcoming various limitations of conventional IPTG induction methods. The optimal concentration of lactose, glucose, and glycerol for maximum expression of DAEase was determined to be 1.5%, 0.125%, and 1.5%, respectively. Fermentor-scale optimization yielded a maximum amount of this enzyme with 5% inoculant, 300 rpm agitation, and 2 vvm aeration. Purification by affinity and anion exchange chromatography resulted in a sevenfold increase in specific activity with an overall yield of 12% and 43 mg of pure recombinant DAEase per liter of culture. Enzyme assays confirmed that DAEase had catalytic activity in the conversion of D-fructose to D-allulose, which was further confirmed by HPLC analysis. This optimized auto-induction-based strategy demonstrated its potential for large-scale production of DAEase in a cost-effective manner with enhanced reproducibility to meet industrial demands for synthesizing D-allulose.
Copyright: © 2025 Lischer et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.