Selection of quiescent Escherichia coli with high metabolic activity

• Published in: Metabolic engineering Vol. 7; no. 1; pp. 4 - 9
• Main Authors: Sonderegger, Marco, Schümperli, Michael, Sauer, Uwe
• Format: Journal Article
• Language: English
• Published: Belgium Elsevier Inc 2005
• Subjects: Biological Evolution; Bioreactors - microbiology; Cell Culture Techniques - methods; Chemostat selection; Energy Metabolism - physiology; Escherichia coli; Escherichia coli - genetics; Escherichia coli - growth & development; Escherichia coli - isolation & purification; Escherichia coli - metabolism; Evolution; Genetic Engineering - methods; Genetic Variation; Metabolic activity; Metabolic engineering; Mutation; Selection, Genetic; Stationary phase; Evolution; Metabolic engineering; Metabolic activity; Chemostat selection; Stationary phase
• ISSN: 1096-7176; 1096-7184
• DOI: 10.1016/j.ymben.2004.05.005

Sustained metabolic activity in non-growing, quiescent cells can increase the operational life-span of bio-processes and improve process economics by decoupling production from cell growth. Because of the ill-defined molecular nature of this phenotype, we developed selection protocols for the evolution of quiescent Escherichia coli mutants that exhibit high metabolic activity in ammonium starvation-induced stationary phase. The best enrichment procedures were continuously or discontinuously fed ammonium-limited chemostat cultures with a very low dilution rate of 0.03 h −1. After 40 generations of selection, improved mutants with up to doubled catabolic rates in stationary phase were isolated. The metabolically most active clones were identified by screening for high specific glucose uptake rates during ammonium starvation-induced stationary phase in deep-well microtiter plates.