An engineering Escherichia coli mutant with high succinic acid production in the defined medium obtained by the atmospheric and room temperature plasma

Escherichia coli BA002, the ldhA and pflB deletion strain, cannot utilize glucose in nutrient-rich or minimal media anaerobically. Co-expression of heterologous pyruvate carboxylase and nicotinic acid phosphoribosyltransferase in BA002 resulted in a significant increase in cell mass and succinic acid production. Nevertheless, the resultant strain, BA016, still could not grow in a defined medium without tryptone and yeast extract. To solve the problem, a novel atmospheric and room temperature plasma mutation method was employed to generate mutants which can grow in the defined medium. A mutant designated as LL016 was observed to be the best strain that regained the capacity of cell growth and glucose utilization in a defined medium anaerobically. After 120 h of fermentation in the defined medium, 35.0 g/L of glucose was consumed to generate 25.2 g/L of succinic acid. Furthermore, with the highest glucose consumption rate in the dual-phase fermentation, the yield of succinic acid in LL016 reached 0.87 g/g, which was higher than that observed in other strains. From an industrial standpoint, the defined medium is much cheaper than LB medium, which shows a great potential usage for the economical production of succinic acid by LL016.