High-level succinic acid production by overexpressing a magnesium transporter in <i>Mannheimia succiniciproducens</i>

Succinic acid (SA), a dicarboxylic acid of industrial importance, can be efficiently produced by metabolically engineered <i>Mannheimia succiniciproducens</i>. Although the importance of magnesium (Mg²⁺) ion on SA production has been evident from our previous studies, the role of Mg²⁺ ion remains largely unexplored. In this study, we investigated the impact of Mg²⁺ ion on SA production and developed a hyper-SA producing strain of <i>M. succiniciproducens</i> by reconstructing the Mg²⁺ ion transport system. To achieve this, optimal alkaline neutralizer comprising Mg²⁺ ion was developed and the physiological effect of Mg²⁺ ion was analyzed. Subsequently, the Mg²⁺ ion transport system was reconstructed by introducing an efficient Mg²⁺ ion transporter from <i>Salmonella enterica</i>. A high-inoculum fed-batch fermentation of the final engineered strain produced 152.23 ± 0.99 g/L of SA, with a maximum productivity of 39.64 ± 0.69 g/L/h. These findings highlight the importance of Mg²⁺ ions and transportation system optimization in succinic acid production by <i>M. succiniciproducens</i>.