Production of D-allose from D-fructose using immobilized L-rhamnose isomerase and D-psicose 3-epimerase.

Abstract

D-Allose is a rare sugar, can be used as an ingredient in a range of foods and dietary supplements, has alimentary activities, especially excellent anti-cancer effects and used in assisting cancer chemotherapy and radiotherapy, etc. To develop a simple and low-cost process for D-allose production, a one-pot enzymatic process using the substrate of D-fructose, and the recombinant enzymes of D-psicose 3-epimerase (DPE) and L-rhamnose isomerase (L-RhI) was developed. These enzymes were cloned from Ruminococcus sp. and B. subtilis, respectively, successfully expressed in E. coli, extracted and immobilized using anion exchange resin and amino resin, respectively. The mass ratio of D-fructose, D-psicose and D-allose was 6.6:2.4:1.0 when the reaction reached equilibrium after 5h of reaction. Using the low-cost substrate of D-fructose, the reusable immobilized enzymes and the one-pot reaction, the production process is simplified and the production cost is decreased. In addition, to simplify the enzyme extraction and immobilization processes, new methods for enzyme capture and immobilization were developed especially for DPE immobilization. This is the first report for one-pot D-allose production using immobilized L-RhI and DPE.