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[1].

The main products of syngas fermentation include ethanol, butanol, acetic acid, butyric acid, and methane[2]. Certain industrial processes, such as petroleum refining, steel milling, and methods for producing carbon black, coke, ammonia, and methanol, discharge enormous amounts of waste gases containing mainly CO and H2 into the atmosphere either directly or through combustion. Biocatalysts can be exploited to convert these waste gases to chemicals and fuels as, for example, ethanol.[3]

There are several microorganisms, which can produce fuels and chemicals by syngas utilization. These microorganisms are mostly known as acetogens including Clostridium ljungdahlii[4], Clostridium autoethanogenum[5], Eurobacterium limosum[6], Clostridium carboxidivorans P7[7], Peptostreptococcus products[8], and Butyribacterium methylotrophicum[9].

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 ratio of CO to H2[2]. On the other hand, syngas fermentation has limitations such as:

References

  1. ^ a b (Brown, 2003)
  2. ^ a b c Worden, 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
  3. ^ Abubackar, H.N.; Veiga, M. C.; Kennes, C. (2011). "Biological conversion of carbon monoxide: rich syngas or waste gases to bioethanol". Biofuels, Bioproduct &. Biorefineries 5 (1): 93–114. doi:10.1002/bbb.256. 
  4. ^ Klasson, K.T.; Ackerson, M. D.; Clausen, E. C.; Gaddy, J.L. (1992). "Bioconversion of synthesis gas into liquid or gaseous fuels". Enzyme and Microbial Technology 14 (8): 602–608. doi:10.1016/0141-0229(92)90033-K. 
  5. ^ Abrini, J.; Naveau, H.; Nyns, E.J. (1994). "Clostridium autoethanogenum, Sp-Nov, an Anaerobic bacterium that produces ethanol from carbon monoxide". Archives of Microbiology 161 (4): 345–351. doi:10.1007/BF00303591. 
  6. ^ Chang, I. S.; Kim, B. H.; Lovitt, R. W.; 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. doi:10.1016/S0032-9592(01)00227-8. 
  7. ^ Ahmed, A; Lewis, R.S. (2007). "Fermentation of biomass generated syngas:Effect of nitric oxide". Biotechnology and Bioengineering 97 (5): 1080–1086. doi:10.1002/bit.21305. PMID 17171719. 
  8. ^ Misoph, M.; Drake, H.L. (1996). "Effect of CO2 on the fermentation capacities of the acetogen Peptostreptococcus productus U-1". Journal of Bacteriology 178 (11): 3140–3145. PMC 178064. PMID 8655492. http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=178064. 
  9. ^ a b Henstra, A.M.; Sipma, J.; Reinzma, A.; Stams, A.J.M. (2007). "Microbiology of synthesis gas fermentation for biofuel production". Current Opinion in Biotechnology 18 (3): 200–206. doi:10.1016/j.copbio.2007.03.008. PMID 17399976. 

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