How does Thermoanaerobacter ethanolicus regulate its ethanol ferm | 53107
Journal of Fundamentals of Renewable Energy and Applications

Journal of Fundamentals of Renewable Energy and Applications
Open Access

ISSN: 2090-4541

+44 1300 500008

How does Thermoanaerobacter ethanolicus regulate its ethanol fermentation pathway?

World Bioenergy Congress and Expo

June 13-14, 2016 Rome, Italy

Weilan Shao

Jiangsu University, China

Keynote: J Fundam Renewable Energy Appl

Abstract :

Thermoanaerobacter species can efficiently use lignocellulose derived substrates to grow at temperatures above 70�?°C. T. ethanolicus produces ethanol as main fermentation product. The final steps of the ethanol fermentation pathway are redox reactions from acetyl-CoA to ethanol via an acetaldehyde intermediate. AdhA, AdhB and AdhE encoded by genes adhA, adhB and adhE are the key aldehyde/alcohol dehydrogenases to catalyze these reactions. After identifying adhE in T. ethanolicus, we find that the ethanol titer of fermentation is controlled by both transcriptional regulation and the properties of AdhA, AdhB and AdhE. The transcription of dehydrogenase genes is regulated by redox sensing protein, which binds to oprators of different affinities so that adhA, adhB and adhE are expressed at directed time. Real time PCR results show that cells transcribe adhB in the absence of ethanol while the transcription of adhA and adhE needs be induced by a low concentration of ethanol. Further increased ethanol concentrations inhibit the transcription of all these genes. Under imitating physiological conditions, the enzyme AdhE and AdhB play crucial roles of aldehyde and alcohol dehydrogenases, respectively, in ethanol formation. However, the propertied and physiological roles of AdhA were not determined until the enzyme is successfully expressed and purified recently. The main physiological function of AdhA is to control ethanol titer by sensing and consuming ethanol in growing cells. After T. ethanolicus JW200 was transformed by adhA or/ and adhE expression plasmids, the homologous expression of adhE enhenced the ethanol production, while that of adhA reduced the ethanol fermentation levels. These results supports a regulation theory: The limitation of ethanol concentration during fermentation is caused by a systematic regulation through transcriptions and activities of the key enzymes in the ethanol-formation pathway.

Biography :

Weilan Shao obtained PhD dgree in 1993 from the University of Georgia and had Postdoctoral studies in the University of Wisconsin. She has been a Professor in China since 2000. She has published more than 100 papers and has been serving as an Editorial Board Member of Chinese Journal of Biotechnology.