Abstract: In this study, a strain named as LW-2 producing high levels of succinic acid was isolated from bovine rumen contents with a culture medium containing disodium fumarate as the carbon source. Morphological analysis, physiological and biochemical characterization, and phylogenetic analysis based on the 16S rDNA sequence indicated that the strain was Escherichia fergusonii. Using glucose as the carbon source, the optimum fermentation conditions for the production of succinic acid by the strain were as follows: temperature 40 ℃, time 24 h, inoculum amount 2.5%, and MgCO3 as pH regulator at a concentration of 30 g/L. The concentration of succinic acid produced under the optimized conditions was 6.36 g/L, which was 41.96% higher than that before optimization, and the yield of succinic acid was calculated as 21.2%. Using xylose as the carbon source, the optimum fermentation conditions were as follows: temperature 37 ℃, time 66 h, inoculum amount 7.5%, and MgCO3 as pH regulator at a concentration of 30 g/L. The concentration of succinic acid produced under the optimized conditions was 7.51 g/L, which was 42.50% higher than that before optimization, and the yield of succinic acid was calculated as 25.03%. It was found that this strain could produce succinic acid by utilizing glucose or xylose as the carbon source, and xylose gave a higher yield of succinic acid than did glucose. This strain has a huge potential for the production of succinic acid.

Key words: succinic acid; screening; Escherichia fergusonii; anaerobic fermentation