Enhanced Succinic Acid Production And Magnesium Utilization By Overexpression Of Magnesium Transporter Mgta In Escherichia Coli Mutant

Magnesium is required by cells for many important cellular functions, such asacting as the cofactor for many key enzymes in the succinic acid synthesis pathwayduring fermentation. Magnesium transporter encoded by mgtA gene could mediate Mg2+influx into cells as reported. In this study, a novel engineered Eschericha coil strainKMG111was constructed by overexpression of mgtA in E. coli mutant DC1515.Adopting KMG111, low-cost alkaline neutralizer Mg(OH)2could replace MgCO3as thealkaline neutralizer in batch fermentation, and nearly the same amount of succinic acidwas obtained, which was29.38g l-1succinic acid with a yield of0.73g g-1glucose. In a3-L fed-batch fermenter, with Mg(OH)2and NaOH combined as alkaline neutralizer, thesuccinic acid concentration could reach a yield of0.86g g-1reducing sugar. The resultsshowed that overexpression of mgtA could enhance the magnesium utilization, anddecreased the requirement of Mg2+addition into the fermentation broth while highersuccinic acid yield was achieved compared with the original strain. This study is thefirst report to decrease the use of alkaline neutralizer via genetic manipulation forsuccinic acid production, which contributes to the industrialization of this microbialsynthesis process.