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. 2014 Nov 13:2:1-5.
doi: 10.1016/j.meteno.2014.11.001. eCollection 2015 Dec.

Microbial production of 1-octanol: A naturally excreted biofuel with diesel-like properties

M Kalim Akhtar  1 , Hariharan Dandapani  2 , Kati Thiel  2 , Patrik R Jones  3
Affiliations

Microbial production of 1-octanol: A naturally excreted biofuel with diesel-like properties

M Kalim Akhtar et al. Metab Eng Commun. .

Abstract

The development of sustainable, bio-based technologies to convert solar energy and carbon dioxide into fuels is a grand challenge. A core part of this challenge is to produce a fuel that is compatible with the existing transportation infrastructure. This task is further compounded by the commercial desire to separate the fuel from the biotechnological host. Based on its fuel characteristics, 1-octanol was identified as an attractive metabolic target with diesel-like properties. We therefore engineered a synthetic pathway specifically for the biosynthesis of 1-octanol in Escherichia coli BL21(DE3) by over-expression of three enzymes (thioesterase, carboxylic acid reductase and aldehyde reductase) and one maturation factor (phosphopantetheinyl transferase). Induction of this pathway in a shake flask resulted in 4.4 mg 1-octanol L-1 h-1 which exceeded the productivity of previously engineered strains. Furthermore, the majority (73%) of the fatty alcohol was localised within the media without the addition of detergent or solvent overlay. The deletion of acrA reduced the production and excretion of 1-octanol by 3-fold relative to the wild-type, suggesting that the AcrAB-TolC complex may be responsible for the majority of product efflux. This study presents 1-octanol as a potential fuel target that can be synthesised and naturally accumulated within the media using engineered microbes.

Keywords: 1-Octanol; Biofuel; Diesel; Excretion; Fatty alcohol.

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Figures

Fig. 1
Fig. 1
Pathway engineering for the synthesis of 1-octanol. (a) Metabolic scheme depicting the pathway for the production of 1-octanol from glucose and fatty acids in E. coli: (1) fatty acid biosynthesis; (2) thioesterase releases free octanoate from FAS; (3) the CAR maturase, Sfp, prepares CARholo for catalysis; (4) CAR converts the free fatty acid to the corresponding aldehyde and (5) AHR reduces the aldehyde to the corresponding alcohol. (b) Example of GC–MS chromatogram showing the synthesis of 1-octanol. TPC3-Ahr strain was induced in modified minimal medium for 14 h, and analysed for fatty alcohols, as described previously (Akhtar et al., 2013). (c) Distribution of 1-octanol in the two strains E. coli BL21(DE3)=WT, and E. coli BL21(DE3) ΔacrA=AcrA. Abbreviations: Glc, glucose; FAS, fatty acid synthesis; TES, thioesterase; reductase; CAR, carboxylic acid reductase; AHR, aldehyde reductase.
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