Clostridium thermocellum releases coumaric acid during degradation of untreated grasses by the action of an unknown enzyme
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Clostridium thermocellum is an anaerobic thermophile with the ability to digest lignocellulosic biomass that has not been pretreated with high temperatures. Thermophilic anaerobes have previously been shown to more readily degrade grasses than wood. Part of the explanation for this may be the presence of relatively large amounts of coumaric acid in grasses, with linkages to both hemicellulose and lignin. We found that C. thermocellum and cell-free cellulase preparations both release coumaric acid from bagasse and switchgrass. Cellulase preparations from a mutant strain lacking the scaffoldin cipA still showed activity, though diminished. Deletion of all three proteins in C. thermocellum with ferulic acid esterase domains, either singly or in combination, did not eliminate the activity. Further work will be needed to identify the novel enzyme(s) responsible for the release of coumaric acid from grasses and to determine whether these enzymes are important factors of microbial biomass degradation.
KeywordsCoumaric acid esterase Cellulosic ethanol Cellulolytic microorganisms Analytical chemistry
The authors wish to thank Julie Paye for helpful discussion, William Kenealy, and Abigail Foster for providing C. thermocellum cellulase and Dan Olson for providing strain M1668.
Compliance with ethical standards
This research was funded by Mascoma Corporation and the BioEnergy Science Center, a US Department of Energy Bioenergy Research Center supported by the Office of Biological and Environmental Research in the DOE Office of Science. This manuscript has been authored by a contractor of the US Government under contract DE-AC05-00OR22725.
Conflict of interest
The authors of this study have been employed by Mascoma Corporation and/or Enchi Corporation, which have held a financial interest in technology related to C. thermocellum and T. saccharolyticum.
This article does not contain any studies with human participants or animals performed by any of the authors.
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