Purification and characterization of D-allulose 3-epimerase derived from Arthrobacter globiformis M30, a GRAS microorganism

An enzyme that catalyzes C-3 epimerization between (D)-fructose and (D)-allulose was found in Arthrobacter globiformis strain M30. Arthrobacter species have long been used in the food industry and are well-known for their high degree of safety. The enzyme was purified by ion exchange and hydrophobic interaction chromatographies and characterized as a (D)-allulose 3-epimerase ((D)-AE). The molecular weight of the purified enzyme was estimated to be 128 kDa with four identical subunits. The enzyme showed maximal activity and thermostability in the presence of Mg2+. The optimal pH and temperature for enzymatic activity were 7.0-8.0 and 70 degrees C, respectively. The enzyme was immobilized to ion exchange resin whereupon it was stable for longer periods than the free enzyme when stored at below 10 degrees C. In the column reaction, the enzyme activity also maintained stability for more than 4 months. Under these conditions, 215 kg of (D)-allulose produced per liter immobilized enzyme, and this was the highest production yield of (D)-allulose reported so far. These highly stable properties suggest that this enzyme represents an ideal candidate for the industrial production of (D)-allulose. (C) 2016, The Society for Biotechnology, Japan. All rights reserved.