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Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Alfred M. Spormann
Departments of Chemical Engineering, and of Civil & Environmental Engineering
Stanford University
Synthesis of Biofuels on Biocathodes
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Source: The National Academies http://needtoknow.nas.edu/energy/interactive/energy-system.php
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Source: The National Academies http://needtoknow.nas.edu/energy/interactive/energy-system.php
Current bioenergy efforts on nontraditional biomass
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Source: The National Academies http://needtoknow.nas.edu/energy/interactive/energy-system.php
Microbial electrosynthesis
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Synthesis of CO2-neutral Electrofuels
Solar Wind
Nuclear
MicrobialCathodicBiofuel
Reactors
CO2-neutral
Transportation fuels Commodity/Fine
Chemicals
CO2 Usage
H2O, waste
e-
(atmospheric)
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Anode
<CH2O>
Microbial fuel cell
e-
Energy production
Redox potentials
+
-
G<0 G>0
Cathode
½ O2 H2O
G<0 (useful)
CO2
Energetics of Bio-Electrochemical Systems
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Anode
<CH2O>
Microbial fuel cell
e-
Energy production
Cathode
Anode B H2O ½ O2
<CH2O> CO2
Hydrocarbons, Chemicals
G>0
CO2
Microbial electrosynthesis
e-
(solar, renewable, nuclear)
Anode A
Energy consumption
Redox potentials
+
-
G<0 G>0
Cathode
½ O2 H2O
G<0 (useful)
CO2
Energetics of Bio-Electrochemical Systems
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Cath
od
e CO2
Acetate
Coulombic
Efficiency: 85%
(Nevin et al. 2010)
Sporomusa ovata
-400mV
(vs SHE)
Methanobacterium palustre
Cath
ode CO2
Methane
- 700mV
- 900mV
(vs SHE)
Coulombic Efficiency:
80-96%
(Cheng et al. 2010)
(Vilano et al. 2010)
Exoelectrogenic Bacteria
Actinobacillus succinogenes
Fumarate
Succinate
Medox
Medred (Park et al. 1999)
Coulombic Efficiency:
Not Available
-325mV
(vs SHE)
Cath
od
e
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
• Uptake of cathodic electrons and integration into cellular metabolism
• CO2 reduction and designer fuels/chemicals pathways
• Engineering stable microbial communities
• Delivery and activation of electrons to cathode
Cathode Anode Creduced Coxidized Hydrocarbons,
Chemicals CO2
e-
e-
Research Focus in Microbial Electrosynthesis
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Bio-Electrochemical Reactor
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Escherichia coli
Cath
od
e Fumarate
(Surrogate)
Succinate
Medox
Medred
-600mV
(vs SHE)
Shewanella oneidensis
Cath
od
e Fumarate
(Surrogate)
Succinate
Medox
Medred
-500mV
(vs SHE)
Our research platform
Methanogenic archaea C
ath
od
e CO2
Methane Cath
ode CO2
Acetate
Homoacetogenic bacteria
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Fum
arat
e, S
ucc
inat
e
Mediator-controlled cathodic electron
consumption by S. oneidensis MR1
Expected stoichiometry: Fumarate + 2e- + 2H+ Succinate m
mo
l L-1
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Current consumption coupled to fumarate reduction
-360 mV vs. SHE fumarate addition
Electrode attached biofilm of S. oneidensis MR1
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Electrode attached biofilm of S. oneidensis MR1
Expected stoichiometry: Fumarate + 2e- + 2H+ Succinate
Current consumption coupled to fumarate reduction
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Cyclic voltammetry of abiotic and biofilm electrode with fumarate
Electrode attached biofilm of S. oneidensis MR1
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Mediator-controlled cathodic electron
consumption by E. coli using fumarate
0.00
0.05
0.10
0.15
0.20
0.25
0
5
10
15
20
25
30
35
40
45
0 50 100 150 200
OD
(60
0)
Co
nce
ntr
atio
n (m
M)
Time [min]
Fumarate
Succinate
Malate
Series4
Fumarate
Succinate
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Synthesis of CO2-neutral Electrofuels
Solar Wind
Nuclear
MicrobialCathodicBiofuel
Reactors
CO2-neutral
Transportation fuels Commodity/Fine
Chemicals
CO2 Usage
H2O, waste
e-
(atmospheric)
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Anne-Kristin Kaster
Ann Lesnefsky
Holly Sewell
Svenja Lohner
Liliana de la Paz
Dr. Bruce Logan Penn State
Funding: GCEP
Spormann bioelectrofuels team
Dr. Yi Cui Stanford
Blaise Pinaud Jamarillo lab
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Power densities reported on MFCs (normalized to electrode-projected surface)
Logan 2009
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Time [h]
Cu
rren
t [m
A]
Shewanella oneidensis MR-1 (AS84) Cell suspension, 0, 0.1, 0.5 mM MV (prereduced)
0.5 mM MV
0.05/0.1 mM MV
0.1 mM MV
0 mM MV
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Cath
od
e CO2
Acetate
Coulombic
Efficiency: 85%
(Nevin et al. 2010)
Sporomusa ovata
-400mV
(vs SHE)
Geobacter sulfurreducens Fumarate/PCE
Succinate/TCE, cDCE
(Gregory et al, 2010)
Coulombic Efficiency: 65%
(Dumas et al. 2010)
-300mV
(vs SHE)
C
ath
od
e
Methanobacterium palustre
Cath
ode CO2
Methane
- 700mV
- 900mV
(vs SHE)
Coulombic
Efficiency: 80-
96%
(Cheng et al. 2010)
(Vilano et al. 2010)
Exoelectrogenic Bacteria
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Expected Data C
on
cen
tration
Reactan
t, Pro
du
ct C
urr
ent
Time
Addition of e--acceptor
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Escherichia coli: e- + fumarate
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Shewanella oneidensis – Electron
Balance
0
0.1
0.2
0.3
0.4
0.5
0 2 4 6
Ele
ctro
ns
[mm
ol]
Time [h]
e- consumed by fumarate reduction
Cathodic e- consumed
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
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
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Microbial
Electrosynthesis Microbial Fuel Cell
Hydro- carbons, chemicals
CO2
Electron acceptor
Chemically catalyzed
Microbially catalyzed
CO2
Organics
O2
H2O
Microbially catalyzed
Chemically catalyzed
adapted from Rabaey & Rozendal, 2010
Energy production Energy consumption
Anode Cathode
- +
- +
Bio-Electrochemical Systems
Product
H2
H+
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Mediators/Electron shuttles
Methyl Viologen
Neutral Red
Redox potential: -440mV
Oxidized: Transparent
Reduced: Blue
Redox potential: -330mV
Oxidized: Red
Reduced: Transparent
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
-0.4
0
0.4
0.8
1.2
1.6
0 5 10 15 20 25
Elec
tro
ns
[mm
ol]
Time [h]
e- consumed by fumarate reduction
Cathodic e- consumed
Shewanella oneidensis – Electron
Balance
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
0
20
40
60
80
100
0 1 h 4 h 0 o/n 0
Met
han
e (
pe
ak A
rea)
Methanothermobacter
marburgensis
measured results Sp
argi
ng
CO
2/N
2
-500 mV -500 mV
Spar
gin
g C
O2/N
2
Spar
gin
g C
O2/N
2
t
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Fum
arat
e, S
ucc
inat
e
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
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Candidate Microorganisms for Microbial Electrosynthesis
Homoacetogens Methanogens
Constructed microbial communities Engineered microorganisms
CO2 CO2
(Acetate) alkane precursor
(Methane) CH4
Alfred M. Spormann, Stanford: Synthesis of Biofuels on Biocathodes
Escherichia coli
Cath
od
e Fumarate
(Surrogate)
Succinate
Medox
Medred
-600mV
(vs SHE)
Shewanella oneidensis
Cath
od
e Fumarate
(Surrogate)
Succinate
Medox
Medred
-500mV
(vs SHE)
Spormann lab
Spormann lab
Exoelectrogenic Bacteria
Cath
od
e CO2
Acetate
Coulombic
Efficiency: 85%
(Nevin et al. 2010)
Sporomusa ovata
-400mV
(vs SHE)