Simultaneous utilization of glucose, xylose and arabinose in the presence of acetate by a consortium of Escherichia coli strains.
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.


RESULTS
In a first stage, a strain unable to utilize glucose, xylose and arabinose (ALS1392, strain E. coli C ptsG manZ glk crr xylA araA) removed 3 g/L acetate within 30 hours. In a subsequent second stage, three E. coli strains (ALS1370, ALS1371, ALS1391), which are each engineered to utilize only one sugar, together simultaneously utilized glucose, xylose and arabinose. The effect of non-metabolizable sugars on the metabolism of the target sugar was minimal. Additionally the deletions necessary to prevent the consumption of one sugar only minimally affected the consumption of a desired sugar. For example, the crr deletion necessary to prevent glucose consumption reduced xylose and arabinose utilization by less than 15% compared to the wild-type. Similarly, the araA deletion used to exclude arabinose consumption did not affect xylose- and glucose-consumption.


CONCLUSIONS
Despite the modest reduction in the overall rate of sugar consumption due to the various deletions that were required to generate the consortium of strains, the approach constitutes a significant improvement in any single-organism approach to utilize sugars found in lignocellulosic hydrolysate in the presence of acetate.
Center for Molecular BioEngineering, Department of Biological and Agricultural Engineering, University of Georgia, Athens, GA 30602, USA.
Tian
T
Xia
Mark A
MA
Eiteman
Elliot
E
Altman
D019342:Acetic Acid / Q000378:metabolism*; D001089:Arabinose / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000254:growth & development*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D005285:Fermentation; D005818:Genetic Engineering; D005947:Glucose / Q000378:metabolism*; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System / Q000235:genetics / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
D029968:Escherichia coli Proteins; C032242:crr protein, E coli; D014994:Xylose; D001089:Arabinose; D010731:Phosphoenolpyruvate Sugar Phosphotransferase System; C031629:phosphoenolpyruvate-glucose phosphotransferase; D005947:Glucose; D019342:Acetic Acid