Isobutanol production

Figure 5.2 Isobutanol production via vaiine pathway and 1-butanol production via CoA-dependent pathway implemented. Common enzyme abbreviations or gene symbols ilvIH, acetolactate synthase ( . coli) aIsS, aceto-lactate synthase (Bacillus subtilis) ilvC, ace-tohydroxy acid isomeroreductase ( . coli) ilvD, dihydroxy acid dehydratase ( . coli) kivd, ketoisovalerate decarboxylase (Lactoccus...

Baez, A., Cho, K.-M., and Liao, J.C. (2011) High-flux isobutanol production using engineered Escherichia coli a bioreactor study with in situ product removal. Appl Microbiol Biotechnol, 90, 1681-1690. 

An evolutionary strategy for isobutanol production strain development... 

Lin, P.P. et al (2014) Isobutanol production at elevated temperatures in thermophilic Geobacillus thermoglucosi-dasius. Metab. Eng., 24, 1-8. 

Desai, S.H., Rabinovitch-Deere, C.A., Tashiro, Y., and Atsumi, S. (2014) Isobutanol production from cellobiose in Escherichia coli. Appl. Microbiol. Biotechnol, 98, 3727—3736. 

S., Ziert, C., Youn, J.W., Wendisch, V.E, and Eikmanns, B.J. (2011) Corynebacterium glutamicum tailored for efficient isobutanol production. Appl Environ. Microbiol, 77 (10), 3300-3310. 

K., Tezuka, H., and Kondo, A. (2013) Increased isobutanol production in Saccharomyces cerevisiae by eliminating competing pathways and resolving cofactor imbalance. Microb. Cell Fact, 12, 119. 

Isobutanol production as an alternative metabolic sink to rescue the growth deficiency of the glycogen mutant of Synechococcus elongatus PCC 7942. Photosynth. Res., 120, 301-310. 

Trinh, C.T. (2012) Elucidating and reprogramming Escherichia coli metabolisms for obligate anaerobic n-butanol and isobutanol production. Appl Microbiol Biotechnol, 95, 1083-1094. 

Methyl-butanol (2MB) is synthesized via the isoleucine pathway (Figure 15.4), which is similar to the valine biosynthesis pathway. One of the challenges for 2MB production is that it passes over the same cassette of genes as in isobutanol production. A recent study [106] indicated that enhancing the citramalate pathway to direct the carbon flux from pyruvate to a-ketobutyrate led 2MB production to about 200 mg 1" with minimum side products such as 1-propanol and isobutanol. 

All of the above-mentioned examples for fermentative isobutanol production were performed in simple flasks or bottles. However, the development of feasible production processes is challenging since not only common upscale problems arise, but also the cytotoxicity of higher alcohols is a striking problem for the transfer into the industrial scale. 

Synthesis gas, a mixture of mainly CO, CO2, and H2, has been used in chemical industry as feedstock and can be generated by gasification of coal and oil but also from biomass, municipal waste, or by recycling of used plastics (Kopke et al., 2010). Isobutanol production from synthesis gas has so far not been reported. However, Kopke et al. (2010) engineered Clostridium ljungdahlii, which is naturally able to use synthesis gas as carbon and energy source, for the production of 1-butanol by implementation of the CoA-dependent 1-butanol synthesis pathway from Clostridium acetobutylicum. The final titer of about 0.5 mM 1-butanol was rather low however, this approach demonstrated the feasibility to produce fuels and chemicals from synthesis gas. 

Blombach B, Eikmanns BJ. (2011). Current knowledge on isobutanol production with Escherichia coli, Bacillus subtilis and Corynebacterium glutamicum. Bioeng Bugs, 2, 346-350. 

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