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ATP drives direct photosynthetic production of 1-butanol in cyanobacteria

Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, CA 90095, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.81). 04/2012; 109(16):6018-23. DOI: 10.1073/pnas.1200074109
Source: PubMed

ABSTRACT While conservation of ATP is often a desirable trait for microbial production of chemicals, we demonstrate that additional consumption of ATP may be beneficial to drive product formation in a nonnatural pathway. Although production of 1-butanol by the fermentative coenzyme A (CoA)-dependent pathway using the reversal of β-oxidation exists in nature and has been demonstrated in various organisms, the first step of the pathway, condensation of two molecules of acetyl-CoA to acetoacetyl-CoA, is thermodynamically unfavorable. Here, we show that artificially engineered ATP consumption through a pathway modification can drive this reaction forward and enables for the first time the direct photosynthetic production of 1-butanol from cyanobacteria Synechococcus elongatus PCC 7942. We further demonstrated that substitution of bifunctional aldehyde/alcohol dehydrogenase (AdhE2) with separate butyraldehyde dehydrogenase (Bldh) and NADPH-dependent alcohol dehydrogenase (YqhD) increased 1-butanol production by 4-fold. These results demonstrated the importance of ATP and cofactor driving forces as a design principle to alter metabolic flux.

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    • "An exogenous MVA pathway was introduced into the cyanobacterium Synechocystis PCC 6803, coupled with the heterologous expression of an isoprene synthase, in which the isoprene yield only reached 250 lg/g gcw (Bentley et al., 2014). A possible reason for the low terpene yield through the MVA pathway is that acetyl-CoA pool in photosynthetic organisms is low under photosynthetic conditions (Lan and Liao, 2012). Compared to cyanobacteria, the plant and algae MEP pathway enzymes are compartmentalized in chloroplasts. "
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    • "Unlike Hbd, PhaB produces the R form of 3-hydroxybutyryl–CoA instead of the S form (21). Since Crt does not accept the R form of 3-HB–CoA, it needs to be replaced with the R-form-specific dehydratase PhaJ (18). The use of PhaB-PhaJ as well as NADPH-specific aldehyde and alcohol dehydrogenases was successfully employed for the enhanced 1-butanol production from CO2 in cyanobacteria (22). "
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    • "Recently, these prokaryotes have received increasing attention in applied research. Cyanobacterial production of bioenergy, such as hydrogen [1] or butanol [2], has been shown, and large-scale projects are believed to become part of sustainable and environmentally friendly bio-production in the future [3]. It is the computational biology which plays a key role in planning the cyanobacteria-based bio-production as well as in data evaluation and the understanding of cellular processes in cyanobacteria. "
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