synthesis of biofuels on biocathodes - stanford university · 2011-10-13 · alfred m. spormann,...

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


Source: The National Academies http://needtoknow.nas.edu/energy/interactive/energy-system.php



Current bioenergy efforts on nontraditional biomass



Microbial electrosynthesis


Synthesis of CO2-neutral Electrofuels

Solar Wind

Nuclear

MicrobialCathodicBiofuel

Reactors

CO2-neutral

Transportation fuels Commodity/Fine

Chemicals

CO2 Usage

H2O, waste

e-

(atmospheric)


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


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


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


• 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


Bio-Electrochemical Reactor


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


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


Current consumption coupled to fumarate reduction

-360 mV vs. SHE fumarate addition

Electrode attached biofilm of S. oneidensis MR1



Expected stoichiometry: Fumarate + 2e- + 2H+ Succinate

Current consumption coupled to fumarate reduction


Cyclic voltammetry of abiotic and biofilm electrode with fumarate



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


Synthesis of CO2-neutral Electrofuels

Solar Wind

Nuclear

MicrobialCathodicBiofuel

Reactors

CO2-neutral

Transportation fuels Commodity/Fine

Chemicals

CO2 Usage

H2O, waste

e-

(atmospheric)


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


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

Logan 2009


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


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)



Expected Data C

on

cen

tration

Reactan

t, Pro

du

ct C

urr

ent

Time

Addition of e--acceptor


Escherichia coli: e- + fumarate


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


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

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+


Mediators/Electron shuttles

Methyl Viologen

Neutral Red

Redox potential: -440mV

Oxidized: Transparent

Reduced: Blue

Redox potential: -330mV

Oxidized: Red

Reduced: Transparent


-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


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


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


Candidate Microorganisms for Microbial Electrosynthesis

Homoacetogens Methanogens

Constructed microbial communities Engineered microorganisms

CO2 CO2

(Acetate) alkane precursor

(Methane) CH4


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


Cath

od

e CO2

Acetate

Coulombic

Efficiency: 85%

(Nevin et al. 2010)

Sporomusa ovata

-400mV

(vs SHE)

synthesis of biofuels on biocathodes - stanford university · 2011-10-13 · alfred m. spormann,...

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