Syngas fermentation

Syngas fermentation, also known as synthesis gas fermentation, is a microbial process. In this process, a mixture of hydrogen, carbon monoxide, and carbon dioxide, known as syngas, is used as carbon and energy sources, and then converted into fuel and chemicals by microorganisms(Brown, 2003)] . The main products of syngas fermentation include ethanol, butanol, acetic acid, butyric acid, and methaneWorden, R.M., Bredwell, M.D., and Grethlein, A.J. (1997). Engineering issues in synthesis gas fermentations, Fuels and Chemicals from Biomass. Washington, DC: American Chemical Society, 321-335] .

There are several microorganisms which can produce fuels and chemicals by syngas utilization. These microorganisms are mostly known as acetogens including "Clostridium ljungdahlii"Klasson, K.T., Ackerson, M. D., Clausen, E. C., and Gaddy, J.L. (1992). Bioconversion of synthesis gas into liquid or gaseous fuels. "Enzyme and Microbial Technology", 14(8), 602-608.] , "Clostridium autoethanogenum"Abrini, J., Naveau, H., and Nyns, E.J. (1994). "Clostridium autoethanogenum", Sp-Nov, an Anaerobic bacterium that produces ethanol from carbon monoxide. "Archives of Microbiology", 161(4), 345-351.">] , "Eurobacterium limosum"Chang, I. S., Kim, B. H., Lovitt, R. W., and Bang, J. S. (2001). Effect of CO partial pressure on cell-recycled continuous CO fermentation by "Eurobacterium limosum KIST612". "Process Biochemistry", 37(4), 411-421..] , "Clostridium carboxidivorans P7"Ahmed, A, and Lewis, R.S. (2007). Fermentation of biomass generated syngas:Effect of nitric oxide. "Biotechnology and Bioengineering", 97(5), 1080-1086.] , "Peptostreptococcus products"Misoph, M., and Drake, H.L. (1996). Effect of CO₂ on the fermentation capacities of the acetogen "Peptostreptococus products U-1". "Journal of Bacteriology", 178(11), 3140-3145.] , and "Butyribacterium methylotrophicum"Henstra, A.M., Sipma, J., Reinzma, A., and Stams, A.J.M. (2007). Microbiology of synthesis gas fermentation for biofuel production. "Current Opinion in Biotechnology", 18(3), 200-206] .

Syngas fermentation process has advantages over a chemical process since it takes places at lower temperature and pressure, has higher reaction specificity, tolerates higher amounts of sulfur compounds, and does not require a specific CO:H₂. On the other hand, syngas fermentation has limitations such as:
* Gas-liquid mass transfer limitationHenstra, A.M., Sipma, J., Reinzma, A., and Stams, A.J.M. (2007). Microbiology of synthesis gas fermentation for biofuel production. "Current Opinion in Biotechnology", 18(3), 200-206.]
* Low volumetric productivity, and
* Inhibition of organisms .

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