Effect of Culture Conditions on the production of Succinate by Enterococcus faecalis RKY1

Abstract

Bioconversion of fumarate to succinate was anaerobically conducted in a synthetic medium containing glycerol as a hydrogen donor and fumarate as a hydrogen acceptor. We investigated the effects of pH, carbon and nitrogen sources, conversion substrate, and other culture conditions on the production of succinate using a newly isolated Enterococcus faecalis RKY1. Addition of a variety of carbonates to the medium significantly increased the rates of production of succinate. The production of succinate and cell growth were relatively satisfactory in the pH range of 7.0- 7.6. By using glycerol as a hydrogen donor, high purity succinate was produced with few byproducts. Yeast extract as a sole nitrogen source was the most effective for producing succinate. As a result, the optimum condition of bioconversion was obtained at a medium containing 20 g/l glycerol, 50 g/l fumarate, 15 g/l yeast extract. 10 g/l K 2 HPO 4 , 1 g/l NaCl, 50 ppm MgCl 2 . 6H 2 O, 10 ppm FeSO 4 . 7H 2 O, and 5 g/l Na 2 CO 3 at pH7.0-7.6. Under the optimum condition, a succinate concentration of 153 g/l was produced in 36 h. The total volumetric production rate and the molar yield of succinate were 4.3 g/l/h and 85%, respectively.