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Applied Microbiology and Biotechnology

, Volume 88, Issue 1, pp 199–208 | Cite as

Metabolic engineering to improve ethanol production in Thermoanaerobacter mathranii

  • Shuo Yao
  • Marie Just Mikkelsen
Applied Genetics and Molecular Biotechnology

Abstract

Thermoanaerobacter mathranii can produce ethanol from lignocellulosic biomass at high temperatures, but its biotechnological exploitation will require metabolic engineering to increase its ethanol yield. With a cofactor-dependent ethanol production pathway in T. mathranii, it may become crucial to regenerate cofactor to increase the ethanol yield. Feeding the cells with a more reduced carbon source, such as mannitol, was shown to increase ethanol yield beyond that obtained with glucose and xylose. The ldh gene coding for lactate dehydrogenase was previously deleted from T. mathranii to eliminate an NADH oxidation pathway. To further facilitate NADH regeneration used for ethanol formation, a heterologous gene gldA encoding an NAD+-dependent glycerol dehydrogenase was expressed in T. mathranii. One of the resulting recombinant strains, T. mathranii BG1G1 (Δldh, P xyl GldA), showed increased ethanol yield in the presence of glycerol using xylose as a substrate. With an inactivated lactate pathway and expressed glycerol dehydrogenase activity, the metabolism of the cells was shifted toward the production of ethanol over acetate, hence restoring the redox balance. It was also shown that strain BG1G1 acquired the capability to utilize glycerol as an extra carbon source in the presence of xylose, and utilization of the more reduced substrate glycerol resulted in a higher ethanol yield.

Keywords

Metabolic engineering Ethanol production Thermoanaerobacter Glycerol dehydrogenase Lactate dehydrogenase 

Notes

Acknowledgments

We thank Slawomir Dabrowski (A&A Biotechnology, Poland) for kindly providing the pYPA vector, Karin Marie Due for taking good care of the continuous reactor, and Klaus Breddam for scientific and linguistic proofreading of the manuscript.

Supplementary material

253_2010_2703_MOESM1_ESM.doc (113 kb)
ESM 1 (DOC 113 kb)

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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.BioScience and Technology Group, BioCentrumTechnical University of DenmarkLyngbyDenmark
  2. 2.BioGasol ApSBallerupDenmark
  3. 3.Biosystems Department, Risø National Laboratory for Sustainable EnergyTechnical University of DenmarkRoskildeDenmark

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