Production of l-erythrose via l-Erythrulose from erythritol using microbial and enzymatic reactions

Abstract

A rare aldotetrose, l-erythrose, was produced from erythritol via a two-step reaction. In the first step, complete oxidation of erythritol to l-erythrulose was achieved by using Gluconobacter frateurii IFO 3254. Washed cell suspension of the strain grown on tryptic soy broth (TSB) supplemented with 1% d-sorbitol was used to carry out the transformation reaction at 30°C with shaking at 170 rpm. At 10% substrate concentration, 98% erythritol was converted to l-erythrulose within 48 h. The produced l-erythrulose was then used as a substrate for the production of l-erythrose. The isomerization of l-erythrulose to l-erythrose was carried out using constitutively produced l-ribose isomerase ( l-RI) from the mutant strain Acinetobacter sp. DL-28 grown on d-lyxose mineral salt medium. At equilibrium, the yield of l-erythrose from l-erythrulose was 18% and finally 1.7 g l-erythrose was obtained from 10 g erythritol. After a number of simple purification steps, the product was isolated from the reaction mixture by ion-exchange column chromatography (Dowex 50W-X2, Ca 2+). The structure of the product was determined after NaBH 4 reduction from Infrared (IR) and 13C nuclear magnetic resonance (NMR) spectra.