title: Nanowire-bacteria hybrids for unassisted solar carbon dioxide fixation to value-added chemicals.
abstract: Direct solar-powered production of value-added chemicals from CO2 and H2O, a process that mimics natural photosynthesis, is of fundamental and practical interest. In natural photosynthesis, CO2 is first reduced to common biochemical building blocks using solar energy, which are subsequently used for the synthesis of the complex mixture of molecular products that form biomass. Here we report an artificial photosynthetic scheme that functions via a similar two-step process by developing a biocompatible light-capturing nanowire array that enables a direct interface with microbial systems. As a proof of principle, we demonstrate that a hybrid semiconductor nanowire-bacteria system can reduce CO2 at neutral pH to a wide array of chemical targets, such as fuels, polymers, and complex pharmaceutical precursors, using only solar energy input. The high-surface-area silicon nanowire array harvests light energy to provide reducing equivalents to the anaerobic bacterium, Sporomusa ovata, for the photoelectrochemical production of acetic acid under aerobic conditions (21% O2) with low overpotential (η < 200 mV), high Faradaic efficiency (up to 90%), and long-term stability (up to 200 h). The resulting acetate (∼6 g/L) can be activated to acetyl coenzyme A (acetyl-CoA) by genetically engineered Escherichia coli and used as a building block for a variety of value-added chemicals, such as n-butanol, polyhydroxybutyrate (PHB) polymer, and three different isoprenoid natural products. As such, interfacing biocompatible solid-state nanodevices with living systems provides a starting point for developing a programmable system of chemical synthesis entirely powered by sunlight.
authors.forename: Chong
authors.initials: C
authors.lastname: Liu
authors.forename: Joseph J
authors.initials: JJ
authors.lastname: Gallagher
authors.forename: Kelsey K
authors.initials: KK
authors.lastname: Sakimoto
authors.forename: Eva M
authors.initials: EM
authors.lastname: Nichols
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Chang
authors.forename: Michelle C Y
authors.initials: MC
authors.lastname: Chang
authors.affiliation: %Kavli Energy NanoSciences Institute, Berkeley, California 94720, United States.
authors.forename: Peidong
authors.initials: P
authors.lastname: Yang
mesh_terms: D001419:Bacteria / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry; D053770:Nanowires / Q000737:chemistry*; D010788:Photosynthesis; D012825:Silicon / Q000737:chemistry; D012993:Solar Energy; D013472:Sunlight; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D002245:Carbon Dioxide; D006859:Hydrogen; D012825:Silicon
keywords: Nanowires; artificial photosynthesis; bacteria; carbon dioxide fixation
references.citation: Science. 2010 Dec 3;330(6009):1355-8
references.pmid: 21127247
references.citation: Nat Biotechnol. 1997 Jan;15(1):63-7
references.pmid: 9035108
references.citation: Nat Chem Biol. 2007 May;3(5):274-7
references.pmid: 17438551
references.citation: Curr Opin Biotechnol. 2013 Jun;24(3):385-90
references.pmid: 23465755
references.citation: Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15612-6
references.pmid: 22547794
references.citation: Acc Chem Res. 2009 Dec 21;42(12):1899-909
references.pmid: 19757805
references.citation: Nat Chem Biol. 2011 Apr;7(4):222-7
references.pmid: 21358636
references.citation: Annu Rev Phys Chem. 2012;63:541-69
references.pmid: 22404587
references.citation: Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15622-7
references.pmid: 22904185
references.citation: Proc Natl Acad Sci U S A. 2008 Aug 5;105(31):10654-8
references.pmid: 18667702
references.citation: Proc Natl Acad Sci U S A. 2014 Sep 30;111(39):14057-61
references.pmid: 25225379
references.citation: J Am Chem Soc. 2008 May 21;130(20):6342-4
references.pmid: 18439010
references.citation: Nano Lett. 2013 Jun 12;13(6):2989-92
references.pmid: 23647159
references.citation: Science. 2011 May 13;332(6031):805-9
references.pmid: 21566184
references.citation: Acc Chem Res. 2009 Dec 21;42(12):1890-8
references.pmid: 19902921
references.citation: Proc Natl Acad Sci U S A. 2012 Sep 25;109(39):15560-4
references.pmid: 23019352
references.citation: Nat Chem. 2009 Apr;1(1):7
references.pmid: 21378780
references.citation: Chem Rev. 2013 Aug 14;113(8):6621-58
references.pmid: 23767781
references.citation: Nature. 2014 Apr 24;508(7497):504-7
references.pmid: 24717429
references.citation: Science. 2011 Nov 4;334(6056):645-8
references.pmid: 21960528
references.citation: Proc Natl Acad Sci U S A. 2006 Oct 24;103(43):15729-35
references.pmid: 17043226
references.citation: J Am Chem Soc. 2014 Oct 1;136(39):13518-21
references.pmid: 25237714
references.citation: MBio. 2010 May 25;1(2):null
references.pmid: 20714445
references.citation: Science. 1998 Apr 17;280(5362):425-7
references.pmid: 9545218
references.citation: Science. 2014 Sep 26;345(6204):1593-6
references.pmid: 25258076
references.citation: Chem Soc Rev. 2009 Jan;38(1):185-96
references.pmid: 19088973