Conversion of Syngas to Ethanol Using Microorganisms
There are two methods to convert biomass-derived synthesis gas to ethanol. The first method is to use biocatalysts and the second method is to use metal-based chemical catalysts. Biocatalysis, or fermentation route, is a relatively new technology. In this approach microorganisms that can convert CO, CO2 and H2 in the syngas to biofuels are used as the biocatalyst and are exposed to syngas by bubbling the gas through an aqueous culture media solution containing microorganisms. A large variety of microorganisms capable of producing carboxylic acids, hydrocarbons, alcohols, and carbonyl compounds from syngas are known, but in this chapter we will focus mainly on the ethanol producing biocatalysis process. Recent progress in this approach is discussed in four review articles. These reviews include two by Munasinghe et al. [1,2], one by Mohammadi et al. [3] and also a 2011 review written by Wilkins and Atiyeh on microbial production of ethanol from carbon monoxide, where CO metabolism and recent genomic studies are discussed [4].