TY  - JOUR
A1  - Hitschler, Lisa
A1  - Nissen, Laura Sofie
A1  - Kuntz, Michelle
A1  - Basen, Mirko
T1  - Alcohol dehydrogenases AdhE and AdhB with broad substrate ranges are important enzymes for organic acid reduction in Thermoanaerobacter sp. strain X514
T2  - Biotechnology for biofuels
N2  - Background: The industrial production of various alcohols from organic carbon compounds may be performed at high rates and with a low risk of contamination using thermophilic microorganisms as whole-cell catalysts. Thermoanaerobacter species that thrive around 50–75 °C not only perform fermentation of sugars to alcohols, but some also utilize different organic acids as electron acceptors, reducing them to their corresponding alcohols. Results: We purified AdhE as the major NADH- and AdhB as the major NADPH-dependent alcohol dehydrogenase (ADH) from the cell extract of the organic acid-reducing Thermoanaerobacter sp. strain X514. Both enzymes were present in high amounts during growth on glucose with and without isobutyrate, had broad substrate spectra including different aldehydes, with high affinities (< 1 mM) for acetaldehyde and for NADH (AdhE) or NADPH (AdhB). Both enzymes were highly thermostable at the physiological temperature of alcohol production. In addition to AdhE and AdhB, we identified two abundant AdhA-type ADHs based on their genes, which were recombinantly produced and biochemically characterized. The other five ADHs encoded in the genome were only expressed at low levels. Conclusions: According to their biochemical and kinetic properties, AdhE and AdhB are most important for ethanol formation from sugar and reduction of organic acids to alcohols, while the role of the two AdhA-type enzymes is less clear. AdhE is the only abundant aldehyde dehydrogenase for the acetyl-CoA reduction to aldehydes, however, acid reduction may also proceed directly by aldehyde:ferredoxin oxidoreductase. The role of the latter in bio-alcohol formation from sugar and in organic acid reduction needs to be elucidated in future studies.
KW  - Thermoanaerobacter
KW  - Thermophile
KW  - Ethanol fermentation
KW  - Organic acid reduction
KW  - Alcohol dehydrogenase
KW  - Aldehyde:ferredoxin oxidoreductase
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/64538
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-645381
SN  - 1754-6834
N1  - The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
N1  - Open Access funding enabled and organized by Projekt DEAL. The authors would like to thank the German Research Foundation DFG (Deutsche Forschungsgemeinschaft) for supporting the research. The work towards the manuscript was funded by the grant DFG BA5757/1-1.
VL  - 14
IS  - art. 187
SP  - 1
EP  - 17
PB  - BioMed Central
CY  - London
ER  -