Production of D-psicose from D-fructose by whole recombinant cells with high-level expression of D-psicose 3-epimerase from Agrobacterium tumefaciens

The specific activity of recombinant Escherichia coli cells expressing the double-site variant (133L-S213C) D-psicose 3-epimerase (DPEase) from Agrobacterium tumefaciens was highest at 24 h of cultivation time in Terrific Broth (TB) medium among the media tested. The contents of crude protein and DPEase in recombinant cells at 24 h were 37.0 and 8.6% (w/w), respectively, indicating that the enzyme was highly expressed. The reaction conditions for the production of D-psicose from D-fructose by whole recombinant cells with the highest specific activity were optimal at 60 degrees C, pH 8.5, 4 g/l cells, and 700 g/l D-fructose. Under these conditions, whole recombinant cells produced 230 g/I D-psicose after 40 min, with a conversion yield of 33% (w/w), a volumetric productivity of 345 g/l/h, and a specific productivity of 86.2 g/g/h. These are the highest conversion yield and volumetric and specific productivities of D-psicose from D-fructose by cells reported thus far. (C) 2015, The Society for Biotechnology, Japan. All rights reserved.