Properties of d-allulose 3-epimerase mined from Novibacillus thermophilus and its application to synthesis of d-allulose

Allulose is an epimer of d -fructose with multiple nutritional functions, which can be biologically synthesized from d -fructose employing d -allulose 3-epimerase (DAE). In this study, NCBI database mining approach was applied to screen novel DAEs, and Novibacillus thermophilus DAE (NtDAE) exhibiting a high activity of 273.9 U/(g⋅wet cell weight) was selected for investigation. NtDAE showed optimum reaction temperature and pH at 70 °C and 7.0, respectively. In the presence of Co 2+ , its activity was improved by 100.1 %, and the half-life ( t 1/2 ) values reached up to 846.3, 539.2 and 47.8 min at 40, 50 and 60 °C, respectively. Higher k cat / K m values toward d -allulose indicated that the preferred physiological substrate of NtDAE was d -allulose. The conversion yield of 500 g/L d -fructose to d -allulose at 60 °C achieved 29.7 %, and further enhanced to 51.6 % with adding 1.1 M borate. This study provided a useful guidance of further engineering and application of NtDAE for realization of industrial production of d -allulose.