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Effect of overexpressing nhaA and nhaR on sodium tolerance and lactate production in Escherichia coli

( 2013-01-25) Wu, Xianghao ; Altman, Ronni ; Eiteman, Mark A ; Altman, Elliot

Background: Like other bacteria, Escherichia coli must carefully regulate the intracellular concentration of sodium ion (Na+). During the bacterial production of any organic acid, cations like Na+ invariably accumulate during a process which must maintain a near neutral pH. In this study, the E. coli nhaA gene encoding the Na+/H+ antiporter membrane protein and the nhaR gene encoding the NhaA regulatory protein were overexpressed in wild-type E. coli MG1655 and in MG1655 pflB (ALS1317) which lacks pyruvate formate lyase activity and thus accumulates lactate under anaerobic conditions.
Simultaneous utilization of glucose, xylose and arabinose in the presence of acetate by a consortium of Escherichia coli strains

( 2012-06-07) Xia, Tian ; Eiteman, Mark A ; Altman, Elliot

Background: The efficient microbial utilization of lignocellulosic hydrolysates has remained challenging because this material is composed of multiple sugars and also contains growth inhibitors such as acetic acid (acetate). Using an engineered consortium of strains derived from Escherichia coli C and a synthetic medium containing acetate, glucose, xylose and arabinose, we report on both the microbial removal of acetate and the subsequent simultaneous utilization of the sugars.