CO2: sustainable and economical carbon source in biotechnology

CO₂ is a prime sustainable carbon source. However, biotechnological industrial applications are still limited.

Using renewable carbon sources for producing chemical compounds of interest in an economical way, while decreasing the use of fossil resources, which generate greenhouse gases, has been at the heart of the development of industrial biotechnologies and renewable chemistry. After having used first generation biomasses such as sugars and lipids, the industry is developing today so-called second generation processes, using more sustainable raw materials such as cellulosic sugars or household waste,

. These developments have already taken place in the micro-algae field, in particular for producing specialty products. CO

is particularly interesting in the field of industrial biology owing to the fact that its usage does not compete with a food usage and does not lead to agricultural land-use reallocation. Unfortunatey, the transformation of CO

into products of interest is poorly controlled and still offers a very limited range of industrial solutions in a market of biosourced chemistry which exceeds today $ 100 billion. Two main types of technology are competing for this opportunity:

• The fermentation processes using CO₂ as a carbon source which are being developed by several companies and which rely on the industrialization of microorganisms naturally capable of capturing CO₂ (micro-algae, archeobacteria, some exotic bacteria). Unfortunately, these microorganisms are often poorly adapted to an industrial use owing to weak performances, limited stability and inadequacy with the constraints of an industrial fermentation. Many companies have attempted to take advantage of photosynthesis and in particular of some micro-algae able to produce large quantities of oil, to develop biofuels. Whereas some of them have shown the relevance of such an approach for producing specialties (such as specific fatty acids) none has succeeded in proving its profitability in low-margin applications such as biofuels. This is the case of companies such as Algenol or Cellana in the USA. Others use exotic microorganisms using alternative pathways for capturing CO₂, this is the case of Kiverdi, Electrochaea, or Lanza Tech, the most advanced among them. The latter transforms a mixture of CO₂, CO, and hydrogen (the syngas) to produce ethanol and is currently constructing its two first commercial units in collaboration with Arcelor Mittal in Belgium and Baosteel in China. For its part, EnobraQ develops a fermentation process using CO₂ as a carbon source for producing precursors of both organic syntheses and polymerization.
• The CO₂ chemical transformation processes which are very efficient when CO₂ is not the sole carbon source (as for the production of polyurethane for example) but limited otherwise to the production of low value-added molecules containing short carbon chains (C1 and C2) such as methanol.

Sources:

Bar-Even, A., Noor, E., Lewis, N.E., and Milo, R. (2010). Design and analysis of synthetic carbon fixation pathways. Proc. Natl. Acad. Sci. U. S. A. 107, 8889–8894. Kiyota, H., Okuda, Y., Ito, M., Hirai, M.Y., and Ikeuchi, M. (2014). Engineering of cyanobacteria for the photosynthetic production of limonene from CO2. J. Biotechnol. 185, 1–7. Li, H., Opgenorth, P.H., Wernick, D.G., Rogers, S., Wu, T.-Y., Higashide, W., Malati, P., Huo, Y.-X., Cho, K.M., and Liao, J.C. (2012). Integrated electromicrobial conversion of CO

to higher alcohols. Science 335, 1596. Contact: Michael Krel – CEO, Enobraq – mkrel@enobraq.com