Oral presentation during the XVI National Congress of the Mexican Society of Biotechnology and Bioengineering

1. Electrosíntesis microbiana de
moléculas de interés industrial con
bacterias homoacetogénicas a partir
de la reducción de CO2
Alessandro Carmona*,
Eric Trably and Nicolas Bernet
*http://alessandrocarmona.blogspot.fr/

2. -Context-
NADH
NAD+
NAD+
Fossils fuels
e-
H2 + CO2 Acetate
Classical fermentation
e-
NADH
NAD+
NAD+
e-
e- +CO2 Acetate
e-
Residual CO2
Electrode
Cathode
Microbial electrosynthesis

3. Electron transfer in Bioelectrochemical systems:
bridge between natural environments and applied technologies
NADH
NAD+
NAD+
Potentiostat or
Power source
e-
e-
Organic matter
CO2 e-
Microbial anode
Electricity production from waste!
NADH
NAD+
NAD+
e- + CO2
Potentiostat or
Power source
e-
e-
Reduced
product
e-
Microbial cathode
Molecules from renewable electricity and CO2!
NADH
NAD+
NAD+
e-
Organic matter
CO2
Fe(III) oxide

4. Anode
Cathode
C+
A-
e- e-
Overall view of bioelectrochemical systems
Configuration of a BES: membrane specificity, type of catalysts at both electrodes, and the
source of the reducing power
Harnisch, F. et al., ChemSusChem. 2009; Franks, A.E. et al., Biofuels. 2010; Logan, B.E. et al., Environ. Sci. Technol. 2008
Rabaey, K. et al, Nat. Rev. Micro. 2010. 8(10): p. 706-716
„electrochemical device that exploits living
microbial cells for the bioelectrocatalysis of anodic-
oxidation and/or cathodic-reduction reactions“
Harnisch F. et al. Chem. Asian J. 2012, 7, 466 – 475
e-
Organics
CO2
Microbially
catalysed
Chemially
catalysedor
H2
H+
H2O
O2
Catalysts at the Anode
e-
Electron
acceptor
Product
Microbially
catalysed
Chemially
catalysed
or
Electron
acceptor
Product
Catalysts at the Cathode
C+
A-
A-
C+
C+
A-
or or
no membranecation anion
exchange membrane
Membrane specificity
Power production
Short circuit
e- e-
e-
e- e-
e- e-
Reducing power
Power supply
Renewable energy
or or

5. -Opportunities in MES-

6. H2 evolution
(H2 mediated acetate production)
Direct MES
Marshall (2012)
Marshall (2013)
Labelle (2014)
Lovley‘s group:
S ovata
S. silvacetica
S. Sphaeroides
A. woodii
C. ljunggahli
C. aceticum
M. thermoacetica
Batlle (2015)
Jiang (2013)Jourdin (2014)
Xafenias (2014)
Sun (2013)
of acetate

7. Cathode
NADH
NAD+
NAD+
e-
e-
e- + CO2
Potentiostat
e-
CH3COOH
Medred
Medox
?
?
?
?
Moorella thermoacetica
Clostridium aceticum
Sporomusa sphaeroides
Clostridium ljungdahlii
Sporomusa silvacetica
Acetobacterium woodii
Sporomusa ovata
carbon source
T°
nutrients
pH
biofilm
Microbial electrosynthesis (MES) and e- transfer
mechanisms in monocultures of homoacetogens
What electron transfer
mechanisms are used?
Common growth conditions
for all homoacetogens

8. “Classic microbiology”
Electrochemical reactor
CEM
RE
Cathode Anode
Pt/IrFelt
Gas
Liquid
DSMZ
strains
Liquid
culture
Grown
strains
48 h
3000
rpm
“washed“
pellet
-Electron source:
Electrode at -900 mV vs. SCE
-Carbon source:
NaHCO3
-Electron source:
H2 in gas phase
-Carbon source:
Pyruvate/ Fructose
*DSMZ media:
135, 311, 642,
777 and 879
Average
medium*
1. Sporomusa sphaeroides
2. Sporomusa silvacetica
3. Acetobacterium woodii
4. Moorella thermoacetica
5. Clostridium aceticum
6. Clostridium ljungdahlii
7. Sporomusa ovata
1. Sporomusa sphaeroides
2. Sporomusa silvacetica
3. Acetobacterium woodii
4. Moorella thermoacetica
5. Clostridium aceticum
6. Clostridium ljungdahlii
7. Sporomusa ovata
“Electro-microbiology”

9. Experimental approach
Cronoamperometry
+ Chromatograpy
Scanning electron
microscopy
Cyclic voltammetry
current consumption electron transfer biofilm formation
What type of electron transfer mechanism do
these homoacetogens perform?

10. -Results-

11. “Classic microbiology”
Electrochemical reactor
CEM
RE
Cathode Anode
Pt/IrFelt
Gas
Liquid
DSMZ
strains
Liquid
culture
Grown
strains
48 h
3000
rpm
“washed“
pellet
-Electron source:
Electrode at -900 mV vs. SCE
-Carbon source:
NaHCO3
-Electron source:
H2 in gas phase
-Carbon source:
Pyruvate/ Fructose
*DSMZ media:
135, 311, 642,
777 and 879
Average
medium*
“Electro-microbiology”

12. Detected traces of: Propionate, Butyrate and Valerate only when yeast extract, vitamins and minerals are added
Acetobacterium woodii Sporomusa sphaeroides / Sporomusa silvacetica<
Wodi
Spha
Silva
Wodi
Spha
Silva
• Biofilms were grown by at -900 mV for 20 days
• Wasted medium was replaced by fresh „basal medium“: Vit, Min or Yeast
• Multiple potential tests were carried out with only „basal medium“
Acetate in cathode
100%
50-80%
50-70%

13. rod-shaped cell
slightly curved spherical spores
Kuhner et al., Int. J. Syst. Evol. Microbiol. 1997
Sporomusa
silvacetica
spores
rodes
flagella

17. -Conclusion-
Then, what electron transfer
mechanisms are used in MES of
acetate? Direct or Mediated?

18. Cathode
Nanowire?
0.0
-250
-500
-750
-1000
←Potentialvs.SCE(mV)→
e-
e-
e-
e-
Cytochrome?
NADH
NAD+
NAD+
CO2
e-
CH3COOH
Ef,1
-400 mV
H+/H2
Ef,1
-900 mV
Potentiostat
e-
NADH
NAD+
NAD+
CO2
e-
CH3COOH
e-
e-
e-
e-
e-
Direct ET
Mediated ET

19. Dr. Eric Trably Dr. Nicolas Bernet
We thank you for
your attention…

20. Technology readiness level (TRL)
Microbial fuel cells (MFC), Microbial electrolysis cells (MEC) and Microbial electrosynthesis
actual system proven
in operational environment
system complete and
qualified
system prototype demonstration
in operational environment
technology demonstrated
in relevant environment
technology validated in
relevant environment
technology validated in lab
experimental proof of concept
technology concept formulated
basic principles observed
TRL
9
8
7
6
5
4
3
2
1 2003
2015
2005
2011
2010
MFC
MEC
MES
“Urinetricity” (UK)
Pilots (USA-UK)

21. Microbial electrosynthesis
Who is who in MES (only original research)
USA (14)
Australia (4)
China (3)
Belgium (1)
Canada (1)
India (1)
Germany (1)
France (1)
soon +2 (LBE)
Netherlands (1)
Singapore (1)
26

22. Why microbial electrosynthesis?
Microbial
electrosynthesis
Fuels/Solvents
e-
CO2
CO2
+

23. Why acetate?
Post-processes to convert carboxylates into bulk fuels or solvents
Ketonization
Reduction
Esterification
Acetate
Reduction
Decarbonylation
Reduction
Carbonyl (solvent)
Ester (fuel/solvent)
Alcohol (fuel/solvent)
Alkane (fuel/solvent)
Alkane
(fuel/solvent)
Drawn from Agler, M. et al, Trends in biotechnology. 2011. 29 (2): p. 70-78
Post-processing
step 1
Post-processing
step 2
Post-processing
step 3

24. Common measured parameters
Chromatography/HPLC:
Metabolite production
Cyclic voltammetry:
electrode scan
Chronoamperometry:
electricity consumption
Microscopy:
biofim attachmentBiofilm analysis:
MiSeq sequencing
H2
Acetate
CH4
i/A
t/days

25. CV analysis of a S. silvacetica electroactive biofilm
(only forward CV signal depicted)
After chronoamperometry
at -800 mV
After chronoamperometry
at -400 mV
Before chronoamperometry
(thus, without biofilm)
Cathode
1 2
Potentiostat
CurrentconsumptionCurrentproduction
Inflection point at
Ef: -350 mV vs. SCE
Current consumption