Biological Production of Ethanol from Coal Synthesis Gas

Coal synthesis gas, a mixture of predominantly CO and H₂, with lesser amounts of CH₄, CO₂, and sulfur compounds, represents a valuable feedstock for the biological production of chemicals. This chapter describes the biological utilization of synthesis gas to produce acetate and other chemicals. P. productus, Eubacterium limosum, and A woodii have been utilized in the University of Arkansas laboratories for the production of acetate as a methane intermediate from coal gas. On the basis of thermodynamic considerations, coal gas may be directly converted biologically to many low-molecular-weight compounds, including methanol, ethanol, n-propanol, n-butanol, propionic acid, and acetic acid. The natural tendency for most mixed bacterial cultures is to produce methane from organic substrates. In order to produce alcohols, which are intermediates in methane synthesis, inhibitors must be added to the cultures to block methane production.