Measurement and Analysis of Intracellular ATP Levels in Metabolically Engineered Zymomonas mobilis Fermenting Glucose and Xylose Mixtures

Juan Carlos Sáez-Miranda, Lorenzo Saliceti-Piazza, James D. McMillan

Research output: Contribution to journalArticlepeer-review

19 Scopus Citations


Intracellular adenosine-5′-triphosphate (ATP) levels were measured in a metabolically engineered Zymomonas mobilis over the course of batch fermentations of glucose and xylose mixtures. Fermentations were conducted over a range of pH (5-6) in the presence of varying initial amounts of acetic acid (0-8 g/L) using a 10% (w/v) total sugar concentration (glucose only, xylose only, or 5% glucose/5% xylose mixture). Over the design space investigated, ethanol process yields varied between 56.6% and 92.3% ± 1.3% of theoretical, depending upon the test conditions. The large variation in process yields reflects the strong effect pH plays in modulating the inhibitory effect of acetic acid on fermentation performance. A corresponding effect was observed on maximum cellular specific growth rates, with the rates varying between a low of 0.15 h-1 observed at pH 5 in the presence of 8 g/L acetic acid to a high of 0.32 ± 0.02 h-1 obtained at pH 5 or 6 when no acetic acid was initially present. While substantial differences were observed in intracellular specific ATP concentration profiles depending upon fermentation conditions, maximum intracellular ATP accumulation levels varied within a relatively narrow range (1.5-3.8 mg ATP/g dry cell mass). Xylose fermentations produced and accumulated ATP at much slower rates than mixed sugar fermentations (5% glucose, 5% xylose), and the ATP production and accumulation rates in the mixed sugar fermentations were slightly slower than in glucose fermentations. Results demonstrate that higher levels of acetic acid delay the onset and influence the extent of intracellular ATP accumulation. ATP production and accumulation rates were most sensitive to acetic acid at lower values of pH.

Original languageAmerican English
Pages (from-to)359-368
Number of pages10
JournalBiotechnology Progress
Issue number2
StatePublished - 2006

NREL Publication Number

  • NREL/JA-510-37993


Dive into the research topics of 'Measurement and Analysis of Intracellular ATP Levels in Metabolically Engineered Zymomonas mobilis Fermenting Glucose and Xylose Mixtures'. Together they form a unique fingerprint.

Cite this