Microbial fuel cell

“Microbial fuel cells prepared with Rio de la Plata river freshwater

sediments. Current production and its relationship with the change of anodophilic microbial community.”Sacco, Natalia; Pataccini, Gabriela; Bonetto, Maria Celina; Figuerola, Eva;

Cortón, Eduardo

E-mail [email protected]

Biosensors and Bioanalysis GroupBiosensors and Bioanalysis Group Biochemistry Department-School of Sciences

UBA-Ciudad Universitaria Ciudad Autónoma de Buenos Aires-Argentina

What are 

Microbial Fuel Cells ?

Bacteria

Reducing power

Metabolism

Organic substrates (donor)

Electric Power

Operational principle

A microbial fuel cell (MFC) converts chemical energy, available

in a biodegradable substrate, directly into electricity.

Bacteria can convert a huge variety of organic compounds into CO2, water and energy. The microorganisms use the produced energy to grow and to maintain

their metabolism. However, by using a MFC we can harvest a part of this microbial energy in the form of electricity.

General principles of MFC

Sedimentary Microbial Fuel Cell (SMFC)

  Power is obtained from indigenous microbial communities of the sediments used.

Over 95% of the electrons resulting from anaerobic respiration can be recovered as electricity.

Lovley Nature Reviews Microbiology 4, 497–508 (July 2006) | doi:10.1038/nrmicro1442

How bacteria transfer e- to the electrode?

These bacteria are called "anodophilic."

Shewanella putrefaciens, Geobacter sulfurreducens, Geobacter metallireducens , Desulfuromonas acetoxidans,and Rhodoferax ferrireducens.

Work Protocol

Sampling SiteSampling Site

Excavation and take samples 

SMFC

In situ measured pH, redox potential and T º water and mud.

Put a load resistance

Type BType A

Measure!

Sampling SiteSampling Site

DGGE

Determination of O. M

P=V2/ RI = V/R

Classical microbiological techniques

Results

Effect of distance between electrodes on the current production .

The distance between the anode and cathode was 8, 12, 17, 21 and 31 cm in the mud of SMFC type A (graphite disc electrode).

Higher current densityElectrode  at 12 cm: 22.1 ± 0.34 mA/m2 with n = 2Electrode at 17 cm: 21.4 ± 0.10 mA/m2 with n = 2

Was observed at 221 days after the start

I biomass attached to the anode and the increase of microbial metabolism.

PB 100mM and  pH7

Electrode at 12 cm: 12.2 mA/m2 and Electrode at 17 cm: 13.1 mA/m2

Characteristics of mud and water.

# The redox potential profile of the mud was negative, indicating a reduction potential that is consistent with anoxic zones.

 # The pH was nearly neutral at all depths studied and collected mud.

 # The water pH of 6.4

# The organic carbon content was 1.470.2 % p/p  (n = 3).

Study of current and potential production in type B SMFCs

SM1: mud + sodium acetate Cf 1.7 g/l. SM2 mud without added.SM3: mud + formaldehyde Cf: 5% (v/v).

Effect of addition of acetate.

Effect of electrode type.

Changes in anodophilic microbial

community.

SM3/disck SM1/ rod SM2/disck SM2/rod SM3/rod SM1/disck

0 20 40 60 80 100

0

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J m

ax.

(m

W/m

2)

time (days)

A) SM1 (with acetate)

Polarization curves

Power density obtained with SMFC's. Values are expressed in mW/m2

SMFCs with  acetate and without it differ by approximately 25% between them with both

electrode

0 20 40 60 800

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J(mA/m2)

Pow

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mW

/m2 )

A

0,0

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E (

V)

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/m2 )

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E (

V)

B

SMFC Disk electrode Rods electrode

SM 1 8,72 ± 1,39 (n=3) 13,93 ± 3,87 (n=3)

SM 2 11,75 ± 5,33 (n=3) 18,79 ± 6,95 (n=3)

SM3 0,20 ± 0,02 (n=2) 0,27 ± 0,13 (n=2)

P max.≈ 8.5 mW/m2

P max.≈ 11.5 mW/m2

B) SM2 (without added)

Denaturing Gradient Gel Electrophoresis (DGGE)

The DGGE allows a comparison of band profiles corresponding to the mud and the anodes SM1 and SM2.

The band of SM1 anode is more similar to the mud, presenting greater diversity maybe associated with the addition of an extra carbon source.

t= 3

0 d

t= 9

0 d

SM2 anode seem a lower diversity compared to initial inoculums. This could be due to the enrichment with species capable of adhering to the electrode surface and exchange electrons with it.

Bands submitted to sequence

SM2

SM1

Mud

SEM of the rod electrode in SM2

(a) before placing it in the SMFC (b) electrode after 90 days of experiment in SM1(c) electrode after 90 days of experiment in SM3 ( 10000X)

Most organisms have the same morphology, these bacilli are approximately 1.25 and 2 m. Anodes in SM 1 biofilm  are observed with similar characteristics to those of SM2, but

less dense.

Classical microbiological techniquesIsolate 7 possible candidates

Only one strain was a facultative anaerobic reductive iron.Majority strain was also isolated from the electrodes of the SMFC

Dietzia natronolimnaea

Conclusions

Compared the power densities obtained with both electrode (rod and disk),

the maximum power was observed with rod electrodes, a very cheap and accessible

material.

The addition of acetate to the sedimentary pile did not have a positive

effect on power generation.

Our set-up shows a small portion of the potential of the mud of the river “Rio de La

Plata”, because the organic matter in SMFC was never renewed.

We had a first approximation of the change in the anodophilic microbial community.

Our results with our SMFC, based on freshwater sediments have show

a performance comparable to the values  obtained with SMFC in the marine

environment. Note that this is the first study of a SMFC with Rio de La Plata

river freshwater sediments.

THANK YOU FOR YOUR ATTENTION!

I´m Willing to Hear your Suggestions and Answer your Questions

Integrantes

Dra. Abrevaya Ximena

Lic. Bonetto Maria Celina

Sr. Figueredo Federico

Lic. Forte Giacobone Ana

Lic. Hilding Ohlsson Astrid

Srta Gabriela Pataccini

Sr. Nuñez Pablo

Lic. Rithner Liliana

Lic. Sacco Natalia

Director: Dr. Cortón Eduardo

Study the production of energy from mud from the river “ Rio de La

Plata” throught the use of sedimentary microbial fuel cell and

their relationship to changes at anodophilic microbial community

Types of microbial fuel cells

First generation: using soluble mediators (neutral red, methylene blue, etc..) to transfer electrons from cells to the electrode.

Second generation: the electrons are transfered through the reduction and oxidation of sulfur compounds. 

Third generation: electron transfer is made directly to the electrodes.