Design of Escherichia coli Cell Culture for Regulating Alanine Production under Aerobic Conditions

The intracellular NADH level in Escherichia coli cells harboring alanine dehydrogenase was regulated by introducing formate dehydrogenase from Mycobacterium vaccae. The cells were grown under aerobic culture conditions, with formate feeding to enhance alanine production. In cultures using media supplemented with 89 mM formate, alanine and pyruvate were produced at 49 +/- 3 and 73 +/- 2 mM, respectively, while 108 mM glucose was consumed within a culture time of t = 24 h. The accumulation of alanine (94 +/- 2 mM) was further enhanced by supplementing the culture with additional formate at 89 mM and elevating the oxygenation level during the course of culture at t = 12 h, which also suppressed the accumulation of pyruvate and lactate as by-products.