harnessing microbe-electrode interactions for bioenergy

Harnessing microbe-electrode

interactions for bioenergy

MSU BioEconomy Institute, March 16th, 2016

Dr. Michaela A. TerAvest

Assistant Professor, Biochemistry and Molecular Biology

Thanks to:

Lars Angenent

(Cornell)

LBNL/UC Berkeley Team

MSU

Biomanufacturing abates

global problems

3

environmental

degradation

pollution climate change

Genetically engineered microbes

are essential to biomanufacturing

4Choi, Yong Jun, and Sang

Yup Lee. Nature (2013).

Overhage, Steinbüchel,

and Priefert. AEM (2003).

Farmer and Liao.

Nat Biotech (2000).

fuels chemicals pharmaceuticals

Reliance on native pathways

hinders biomanufacturing

5Martinez et al.

Metab. Eng. (2008).

Further modification can address

specific inefficiencies

6

My approach combines

electrochemistry and synbio

7

Utilizing electrodes to control

metabolic electron flow

8TerAvest and Angenent.

ChemElectroChem (2014).

Shewanella oneidensis MR-1

9

• Isolated from Lake Oneida, NY sediments

• Respires with:– oxygen

– nitrate

– iron

– manganese

– chromium

– uranium

– electrodes

Photo by Dr. Miriam Rosenbaum

Cytochromes connect

electrodes to metabolism

10

Electrode controls

metabolic rate and efficiency

11TerAvest and Angenent.


Electrochemistry is a powerful tool

for metabolic control

12

Understanding energy partitioning

by the electron transport chain

13

ATP DNA replication

PMF transport and motility

NAD(P)H biosynthesis

Electron transport mutant

produces more current than WT

14

How does Δnuo

influence metabolism?

15

Δnuo uses the electrode

less efficiently than WT

16

strain [pyruvate] (mM) mmol e-/mmol lactate

WT 0.8±0.2 0.84±0.06

ΔnuoN 1.4±0.3 0.54±0.09

Metabolomics confirm

metabolic changes

17

Δnuo oxidizes substrate

less completely than WT

18

Electron transport chain

engineering alters energy flow

19

Combining electrodes and

synthetic biology

20

Shewanella oneidensis

• extracellular electron

transfer

• does not utilize sugar

• basic genetic tools

Escherichia coli

• no extracellular

electron transfer

• utilizes sugar

• highly developed

genetic systems

Combining electrodes and

synthetic biology

21

Shewanella oneidensis MR-1

E. coli wild-type

E. coli with Mtr

Jensen, TerAvest and Ajo-Franklin.

In preparation.

Advanced synbio methods

enhance Mtr-E. coli

V1.0 V2.0

22Goldbeck et al.

ACS Synthetic Biology, (2013).

Full pathway expression greatly

improves electron transfer

23Jensen, TerAvest and Ajo-Franklin.

In preparation.

Strain with full pathway survives

like wild-type E. coli

24TerAvest, Zajdel and Ajo-Franklin.


Electrochemical performance of

E. coli is similar to Shewanella

25

Shewanella oneidensis

100-200 fA/cell

Escherichia coli

33 fA/cell

25% efficient 2.5% efficient

Watson and Logan.

Biotech and Bioeng (2009).

Liu et al.

Angew. Chem. (2011).

How does electron transfer impact

intracellular reactions?



Current production is directly

connected to metabolism



Mtr module shifts metabolism toward

more oxidized products

28

strain [formate] (μM) [ethanol] (μM)

ccm 44±13 64±0.6

cymA-mtr n.d. 40±3

TerAvest, Zajdel and Ajo-Franklin.


Electrode interaction enhances

redox balance

29TerAvest, Zajdel and Ajo-Franklin,


Mtr-modified E. coli produce

current with multiple substrates

30

Electrodes harvest reducing

equivalents from glucose

31

Synbio and electrodes relieve

redox balance constraints

32

Using microbial electrochemistry

and synbio to optimize bacteria

33

Dissection and redesign of the

bacterial respiratory powerhouse

34

Knowledge gained will enable

microbial electrosynthesis

35

CO2 +

Acetogens naturally perform

(slow) electrosynthesis

36Nevin, et al.

Mbio (2010).

Acetate production increased

20 times in 5 years

37Patil, et al.

ES&T (2015).

Removing barriers to

inward electron transfer

38Ross et al.

PLoS ONE (2011).

Inward electron transfer will

provide cofactors for synthesis

39

Artistic rendering of Shewanella by Cornell iGEM 2012

harnessing microbe-electrode interactions for bioenergy

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