Growth rate of a non-fermentative Escherichia coli strain is influenced by NAD+ regeneration
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By complementing a non-fermentative Escherichia coli (ldhA − pflB −) strain with the recombinant Zymomonas mobilis ethanol pathway (pdc, adhB), we evaluated the effect of different levels of enzymatic activity on growth rate demonstrating that there is a direct relationship between anaerobic growth rate and the total specific activity of pyruvate decarboxylase, which is the limiting enzyme of this specific fermentative NAD+ regenerating pathway. This relationship was proved to be useful to establish a selection strategy based on growth rate for the analysis of lctE libraries, which encode lactate dehydrogenase from Bacillus subtilis.
KeywordsGrowth rate control Lactate dehydrogenase NAD+ regeneration Non-fermentative Escherichia coli Pyruvate decarboxylase
This work was supported by CONACYT grants 138498, 50952, MOR-2004-C02-048; SAGARPA-2004-C01-224, and DGAPA-UNAM. The authors thank Eugenio López and Jorge Yañez from “Unidad de Síntesis y Secuenciación” (Instituto de Biotecnología, UNAM), Dr. Humberto Flores for technical assistance in the LDH work and Fernando González for HPLC support.
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