Efficient Production of l -Ribose with a Recombinant Escherichia coli Biocatalyst

Abstract

ABSTRACT A new synthetic platform with potential for the production of several rare sugars, with l -ribose as the model target, is described. The gene encoding the unique NAD-dependent mannitol- 1 -dehydrogenase (MDH) from Apium graveolens (garden celery) was synthetically constructed for optimal expression in Escherichia coli . This MDH enzyme catalyzes the interconversion of several polyols and their l -sugar counterparts, including the conversion of ribitol to l -ribose. Expression of recombinant MDH in the active form was successfully achieved, and one-step purification was demonstrated. Using the created recombinant E. coli strain as a whole-cell catalyst, the synthetic utility was demonstrated for production of l -ribose, and the system was improved using shaken flask experiments. It was determined that addition of 50 to 500 μM ZnCl 2 and addition of 5 g/liter glycerol both improved production. The final levels of conversion achieved were >70% at a concentration of 40 g/liter and >50% at a concentration of 100 g/liter. The best conditions determined were then scaled up to a 1-liter fermentation that resulted in 55% conversion of 100 g/liter ribitol in 72 h, for a volumetric productivity of 17.4 g liter −1 day −1 . This system represents a significantly improved method for the large-scale production of l -ribose.