Adaptation of Escherichia coli to elevated sodium concentrations increases cation tolerance and enables greater lactic acid production.

摘要: Adaptive evolution was employed to generate sodium (Na(+))-tolerant mutants of Escherichia coli MG1655. Four with elevated tolerance, designated ALS1184, ALS1185, ALS1186, and ALS1187, were independently isolated after 73 days serial transfer in medium containing progressively greater Na(+) concentrations. The isolates also showed increased tolerance K(+), although this cation not used for selective pressure. None the adapted nonionic osmolyte sucrose. Several physiological parameters E. MG1655 isolate greatest calculated compared using glucose-limited chemostats. Genome sequencing that ALS1187 contained mutations five genes, emrR, hfq, kil, rpsG, sspA, all which could potentially affect ability tolerate Na(+). Two these hfq are known be involved global regulatory processes help cells endure a variety cellular stresses. Pyruvate formate lyase knockouts constructed strains determine whether afforded anaerobic generation lactate. In fed-batch fermentations, pflB generated 76.2 g/liter lactate pflB, only 56.3