Synthesis of Biofuels on Biocathodes

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Kenneth Philip Waters
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1 Synthesis of Biofuels on Biocathodes Alfred M. Spormann Departments of Chemical Engineering, and of Civil & Environmental Engineering Stanford University

2 Source: The National Academies

3 Current bioenergy efforts on nontraditional biomass Source: The National Academies

4 Microbial electrosynthesis Source: The National Academies

5 Synthesis of -neutral Electrofuels H 2 O, waste e - (atmospheric) Usage Solar Wind Nuclear Microbial Cathodic Biofuel Reactors -neutral Transportation fuels Commodity/Fine Chemicals

6 Energetics of Bio-Electrochemical Systems Microbial fuel cell <CH 2 O> Anode e - G<0 (useful) Cathode Redox potentials - G<0 G>0 ½ O 2 H 2 O Energy production +

G>0 + Microbial electrosynthesis <CH 2 O> Anode A Cathode e - Anode B H 2 O ½

7 Energetics of Bio-Electrochemical Systems Microbial fuel cell <CH 2 O> ½ O 2 Anode e - G<0 (useful) Cathode H 2 O Energy production Redox potentials - G<0 G>0 + Microbial electrosynthesis <CH 2 O> Anode A Cathode e - Anode B H 2 O ½ O 2 Hydrocarbons, Chemicals G>0 (solar, renewable, nuclear) Energy consumption

1999) -400mV (vs SHE) Acetate Coulombic Efficiency: 85% (Nevin et al.

8 Exoelectrogenic Bacteria Cathode Cathode Cathode Actinobacillus succinogenes Sporomusa ovata -325mV (vs SHE) Med ox Fumarate Succinate Coulombic Efficiency: Not Available Med red (Park et al. 1999) -400mV (vs SHE) Acetate Coulombic Efficiency: 85% (Nevin et al. 2010) Methanobacterium palustre - 700mV - 900mV (vs SHE) Methane Coulombic Efficiency: 80-96% (Cheng et al. 2010) (Vilano et al. 2010)

Research Focus in Microbial Electrosynthesis e - Anode Cathode C reduced C e - oxidized Hydrocarbons, Chemicals Uptake of cathodic electrons and integration

9 Research Focus in Microbial Electrosynthesis e - Anode Cathode C reduced C e - oxidized Hydrocarbons, Chemicals Uptake of cathodic electrons and integration into cellular metabolism reduction and designer fuels/chemicals pathways Engineering stable microbial communities Delivery and activation of electrons to cathode

10 Bio-Electrochemical Reactor

Cathode Our research platform Cathode Cathode Cathode Methanogenic archaea Homoacetogenic bacteria Methane Acetate Shewanella oneidensis

11 Cathode Our research platform Cathode Cathode Cathode Methanogenic archaea Homoacetogenic bacteria Methane Acetate Shewanella oneidensis -500mV (vs SHE) Med ox Med red Fumarate (Surrogate) Succinate Escherichia coli -600mV (vs SHE) Med ox Fumarate (Surrogate) Med red Succinate

12 Fumarate, Succinate Mediator-controlled cathodic electron consumption by S. oneidensis MR1 Expected stoichiometry: Fumarate + 2e - + 2H + Succinate mmol L -1

13 Electrode attached biofilm of S. oneidensis MR1 Current consumption coupled to fumarate reduction fumarate addition -360 mv vs. SHE

14 Electrode attached biofilm of S. oneidensis MR1 Current consumption coupled to fumarate reduction Expected stoichiometry: Fumarate + 2e - + 2H + Succinate

15 Electrode attached biofilm of S. oneidensis MR1 Cyclic voltammetry of abiotic and biofilm electrode with fumarate

Concentration (mm) OD(600) Mediator-controlled cathodic electron consumption by E. coli using fumarate 45 40 Fumarate 0.

16 Concentration (mm) OD(600) Mediator-controlled cathodic electron consumption by E. coli using fumarate Fumarate Fumarate Succinate Malate Series Succinate Time [min]

17 Synthesis of -neutral Electrofuels H 2 O, waste e - (atmospheric) Usage Solar Wind Nuclear Microbial Cathodic Biofuel Reactors -neutral Transportation fuels Commodity/Fine Chemicals

18 Spormann bioelectrofuels team Liliana de la Paz Ann Lesnefsky Svenja Lohner Holly Sewell Anne-Kristin Kaster Blaise Pinaud Jamarillo lab Dr. Yi Cui Stanford Funding: GCEP Dr. Bruce Logan Penn State

19 Power densities reported on MFCs (normalized to electrode-projected surface) Logan 2009

20 Current [ma] Shewanella oneidensis MR-1 (AS84) Cell suspension, 0, 0.1, 0.5 mm MV (prereduced) 0 mm MV 0.05/0.1 mm MV 0.1 mm MV 0.5 mm MV Time [h]

21 Cathode Cathode Cathode Sporomusa ovata Exoelectrogenic Bacteria -400mV (vs SHE) Coulombic Efficiency: 85% Acetate (Nevin et al. 2010) Geobacter sulfurreducens (Gregory et al, 2010) -300mV (vs SHE) Methanobacterium palustre Fumarate/PCE Succinate/TCE, cdce Coulombic Efficiency: 65% (Dumas et al. 2010) - 700mV - 900mV (vs SHE) Methane Coulombic Efficiency: 80-96% (Cheng et al. 2010) (Vilano et al. 2010)

22 Current Expected Data Addition of e - -acceptor Concentration Reactant, Product Time

23 Escherichia coli: e - + fumarate

24 Electrons [mmol] Shewanella oneidensis Electron Balance e - consumed by fumarate reduction Cathodic e - consumed Time [h]

25 Future Work - Outlook Identify molecular mechanism of electron transport into the cell Optimize shuttle mediated electron transport Explore other mediators & cathode potentials Work with other (engineered) target microorganisms Construct microbial communities, interspecies electron transfer Scale up

Microbial Fuel Cell Microbially catalyzed

Microbial Electrosynthesis Chemically catalyzed

Product Electron acceptor Cathode Hydrocarbons,

26 Microbial Fuel Cell Microbially catalyzed Bio-Electrochemical Systems Chemically catalyzed Microbial Electrosynthesis Chemically catalyzed Microbially catalyzed Organics Anode O 2 H 2 O H + H 2 Product Electron acceptor Cathode Hydrocarbons, chemicals Energy production Energy consumption adapted from Rabaey & Rozendal, 2010

27 Mediators/Electron shuttles Methyl Viologen Neutral Red Redox potential: -440mV Oxidized: Transparent Reduced: Blue Redox potential: -330mV Oxidized: Red Reduced: Transparent

29 Electrons [mmol] Shewanella oneidensis Electron Balance 1.6 e - consumed by fumarate reduction Cathodic e - consumed Time [h]

30 Methane (peak Area) 100 Methanothermobacter marburgensis measured results -500 mv -500 mv Sparging /N 2 Sparging /N 2 Sparging /N h 4 h 0 o/n 0 t

31 Fumarate, Succinate Shewanella oneidensis MR-1 WT (AS579 ) Cell suspension, 0.5 mm MV (added last) Pregrown on 50mM lactate, 70mM + CAA fumarate anaerobically for app. 18h, OD: app. 0.8, -700mV vs Ag/AgCl

32 Candidate Microorganisms for Microbial Electrosynthesis Homoacetogens Methanogens Engineered microorganisms (Acetate) alkane precursor CH 4 (Methane) Constructed microbial communities

33 Exoelectrogenic Bacteria Cathode Cathode Cathode Sporomusa ovata -400mV (vs SHE) Coulombic Efficiency: 85% Acetate (Nevin et al. 2010) Shewanella oneidensis -500mV (vs SHE) Med ox Fumarate (Surrogate) Spormann lab Med red Succinate Escherichia coli -600mV (vs SHE) Med ox Fumarate (Surrogate) Spormann lab Med red Succinate

Bio-electrochemistry course

Bio-electrochemistry course LabMET short course on microbial energy management and microbial fuel cells Peter Aelterman and Korneel Rabaey Course overview Bacterial metabolism and the redox potential Basic