7-04: Microoganisms to produce alcohols or alkanes from hydrogen and carbon dioxide or carbon monoxide

Microorganisms are known to produce low concentrations of acetate and ethanol from H₂ and CO₂ or CO.  The objective of this research was to isolate organisms that could convert such gases to high concentrations of alcohols such as ethanol or 1-butanol or alkanes such as hexane or iso-octane.  Rumen fluid was taken from a fistulated cow and subjected to several 3-to-5 day enrichment incubations in media with alcohols or alkanes to increase tolerance. Microorganisms were selected from diluted enrichment cultures by growing them on agar with H₂ and CO₂ in the headspace. Selected colonies were transferred to broth.  Several colonies produced ethanol from H₂ and CO₂ whether or not ethanol was included in the broth at 0, 6, or 10% concentration.  When ethanol was initially included in the media, greater ethanol was produced from gases than when it was not included and acetate production appeared to be inhibited. Cultures also produced about 10% as much 1-propanol, iso-propanol, or 1-butanol as ethanol.  Isolates that produced alcohols included Enterococcus species (>97% homology with E. avis), and strictly anaerobic gram-negative spiral rods. Cultures selected from hydrocarbon enrichments produced alkanes including hexane and other hydrocarbons of similar size with branching or double carbon bonds.  Fifty isolates that produced alkanes were identified by 16-S r-DNA and were >97% homologous with Actinomyces sp., Enterococcus faecium or E. Hirae, Eschericia coli, Clostridium glycolicum, Proteus sp., or Tissierella sp.  Microorganisms like these could produce fuels from synthesis gases or hydrogen and carbon dioxide (patent pending).