Optimization and Comparative Methods for Efficient D-psicose Production Using Physicochemical and Enzymatic Processes

D-psicose is one of the rare sugars that are gaining more attention. Currently, it is accepted for use in health food products and is also a safe sugar generally recognized as safe (GRAS). Now, it is used in many industries, resulting in an increased market demand; however, there has been only limited technological advancement regarding its production process. Consequently, this research investigated two processes for D-psicose production and optimizing the conditions to achieve highly efficient D-psicose conversion. Two processes were: (1) a physicochemical process using high temperature at different pH values, based on autoclaving, and (2) an enzymatic method using crude and purified recombinant D-psicose 3-epimerase (DPEase). Different fructose concentrations were studied as substrate for the D-psicose conversion in both methods. The results showed that crude DPEase conversion clearly produced the highest yield and D-psicose conversion under the best optimum conditions (50% w/v fructose solution with a reaction time of 180 min) of 14.88% w/v and 28.60%, respectively. DPEase converted fructose specifically to only D-psicose and no other sugars were detected as by-products, while the physicochemical method produced negative changes in both physical and chemical properties, such as a pH reduction and an unacceptable caramelization appearance in the sugar solution, as well many sugars being detected after autoclaving. All the results should be useful as guidelines for further research and development on sugar-based substrates and for improving the efficiency of the DPEase enzyme, including downstream technology to achieve highly efficient D-psicose production at the pilot and industrial scales.