P155: Clostridium coskatii, sp. nov., an Anaerobic Bacterium that Produces Ethanol from Synthesis Gas

Sunday, August 1, 2010
Pacific Concourse (Hyatt Regency San Francisco)
James A. Zahn, Jyotisna Saxena, Young Do, Milind Patel, Seth Fischbein, Rathin Datta and Richard Tobey, Coskata, Inc., Warrenville, IL
Clostridium coskatii sp. nov. was isolated from estuary sediment collected from Coskata-Coatue Wildlife Refuge in Nantucket, MA.  Under anaerobic conditions, the isolate produced ethanol as a primary product from CO and/or H2 and CO2, according to the following reactions:

6CO + 3H2O → C2H5OH+4CO2
6H2 + 2CO2 → C2H5OH + 3H2O

Colonies appeared circular, were white to translucent in color, and slightly raised at the center.  Cells were rarely motile, rod-shaped, stained gram-positive, and occurred singly or in chains.  Electron micrographs showed the elongation of the cells up to 20-30 µm under high volumetric ethanol concentrations, or other physiological stress conditions.  C. coskatii was strictly anaerobic and chemolithoautotrophic growth in the absence of yeast extract occurred with H2 + CO2 or CO.  C. coskatii grew optimally at a pH between 5.8 and 6.5, and at a temperature of 37ºC.  The mol% G+C of the DNA from C. coskatii was 32.5% ± 0.5% G+C, which was 3 to 10% higher than other known ethanologenic clostridia.  Phylogenetic analysis of the 16S rRNA gene sequence indicated that the organism belonged within clostridial rRNA homology group 1.  DNA fingerprinting showed that C. coskatii was most closely related to C. autoethanogenum, C. ljungdahlii PETC, and C. ragsdalei; however, DNA-DNA reassociation values for these pairings were below 66.5%, which verified the status of C. coskatii as new clostridial species.  C. coskatii is the

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