Microbial energy conversion and practical application to an algal fuel cell. Peter Weigele

Microbial energy conversion andpractical application to

an algal fuel cell.

Peter WeigeleMIT Biology and Edgerton CenterBiological Energy Interest Group (BEInG)

Presentation for 10.391 Sustainable Energy February 15, 2007

Department ofBiology

http://visibleearth.nasa.gov/

The Keeling curve

Today’s message:

Life has an incredible diversity of mechanisms for theinterconversion of different forms of energy, includingsunlight, inorganic and organic chemical energy.

Biological productivity and energy conversion underlies fossilfuels, ethanol, biodiesel, and cellulose-based technologies.

The range of respiratory and photosynthetic mechanisms should be examined as a “toolkit” for further development of biological energy conversion technologies.

(need more pedagogical exploration of photosynthesis and cellulose at MIT!)

A Culinary and Cultural Staple in Crisis:Mexico Grapples With Soaring Prices for Corn -- and Tortillas

By Manuel Roig-FranziaWashington Post Foreign ServiceSaturday, January 27, 2007; A01

“Mexico is in the grip of the worst tortilla crisis in its modern history. Dramatically rising international corn prices, spurred by demand for the grain-based fuel ethanol, have led to expensive tortillas.”

Food and fuel subject to the same market forces?

9 x 109 by 2050

Photosynthesis

Organisms make their own food by fixing (reducing) inorganic carbon to make energy rich carbohydrates

Reducing power derived from the light driven oxidation of water (an amazing process).

Carbohydrates subsequently respired for a net gain of NADH and ATP, intracellular energy carriers.

Example: 18 ATP needed to synthesize one glucose, 30 ATP generated by complete oxidation of glucose back to CO2. Energy difference is input of solar energy.

Respiration

All organisms derive their biosynthetic abilities from the stepwise oxidation of energy rich compounds (respiration).

Oxidation generates reduced intracellular electron carriers.

Oxidation of electron carriers is used to establish and maintain chemical gradients across cellular membranes (emf to pmf).

Proton motive force consumed to synthesize ATP, an energy carrier.

ATP synthase

Electrons go where they are most wanted...

Oxygen is a potent electron acceptor.

Freely diffuses across biological membranes.

Electrons can accomplish work as they traverserespiratory systems en route to oxygen.

Aerobic respiration

Aerobic respiration: O2 as terminal electron acceptor

“Bacteria are beautiful” by Diane Newman

Oxygen limited in many environments, e.g. sediments

Bacteria can use minerals as terminal electron acceptors,e.g. Ferric oxides (Iron III)

Electrons are exported out of the cell by soluble, electroncarriers OR by using cell surface protein complexes.

Other example of anaerobic respiration is fermenation(6 ATP/glucose versus 30ATP/glucose).

Anaerobic respiration

Anaerobic respiration with Iron(III) as extracellular terminal e- acceptor

“Bacteria are beautiful” by Diane Newman

solubleelectroncarriers

see also www.geobacter.org

http://www.pnas.org/cgi/doi/10.1073/pnas.0604517103

Protein nanowires also found in gram negative aerobes, cyanobacteria, and methanogens

Schematic of a microbial fuel cell

...anode is a continually replenished electron acceptor!

Sediment battery: a type of microbial fuel cell

Bacterial biomass from electricity

Running a microbial fuel cell in reverse can driveotherwise thermodynamically unfavorable chemistry.

Summary, part I: The microbial fuel cell could be a core technology for energy conversion

microbial metabolismex vivo protein complexes

anode/cathode compositionelectron carriers

fuel cell construction

cellulose-derived carbohydratesenergy rich wastewater

organic sedimentssunlight

electricity

electricityhydrogenalcoholsmethanetreated water

MFC

Part II: Photosynthesis

cyt bfcomplexcyt bf

complex

FNRFNRFdFd

photo-system I(P700)

photo-system I(P700)

LightHarvestingComplex(LHCII)

LightHarvestingComplex(LHCII)

LightHarvesting

Complex(LHCI)

LightHarvesting

Complex(LHCI)

thylakoid lumen

stroma

2 H2O 4 H+ + O2

OECOEC

H+

H+

H+

H+

ADP + Pi ATPNADP+NADPH

photo-system II(P680)

photo-system II(P680)

PCPC

light light

1 23

4

5F1F0

ATP-synthase

Q

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

1

2

3

4

5

Part III:A simple, low-cost algal fuel cell

for research and education

Principle of H2 generation by microalgae

Deprive algae of external oxygen

Diminish their capacity to generate oxygen from water splitting by limiting availability of sulfur

Algae use protons as terminal electron acceptor

Reduced protons make H2, a reaction catalyzed by an oxygen sensitive enzyme called hydrogenase

Pathway explored by Maria Ghirardi, Michael Siebert, Tasios Melis and colleagues

Chlamydomonas rheinhardtii making colonies on solid medium

Photobioreactors: modular, scalable

Algal growth using an airlift bioreactor

Gas Dispersion Tube Only

Airlift with Gas Dispersion Tube

PVC insert to create air-lift for improved mixing

PVC tubing + caps + fittings + tubing + pump = gas recirculator

The finished recirculating pump

Gas managment and fuel cell

Luer fittings and stopcocks fromCole-Parmer

petstore

40 bucks from fuelcellstore.com

Bioreactor setup

Fuel cell under load

Photobioreactor

Fuel Cell

Online Data Monitoring

H2

e-

Data collection using an A/D converter

Dataq model 154, ~$100, microvolt resolution

algal growth on solid substrate

grow algae with bubbling air and S+ medium

inoculate large bioreactor containing S- medium

seal, start pump, and collect data

measure cell mass, and chlorophyll concentration

Experimental overview

Chlamydomonasrheinhardtii

Unknown: “WP2” Unknown: “WP1”

Do other kinds of green, microalgae make H2?

Testing different algal strains (note clumping Chlamy)

Algal strain choice impacts H2 production: As Indicated by Varying Voltage Output

data from 10.28 Team C, 2006

data from 10.28 Team C, 2006

10.28 Team C

Asish Misra

Sohrab Virk

Joia Ramachandani

Sophmore biology students from Nashoba Regional HS

Kay Leigh Kay

Andrew Hoy Mackey Craven

Sam Jewell

Nina Kshetry

Many, many thanks!

Tom KnightJon KingChris Kaiser

Samantha SuttonJason Kelly

openwetware.org

Edgerton CenterSteven BanzaertSandi Lipnonski

New blood!John M. CravenAndrew Hoy

J.F. Hamel and 10.28

Team CJoia RamachandaniAsish MisraSohrab Virk

David Form, NRHSAshley, Meaghan, Kay Leigh, Jackie, and Kay

6 CO2 + 6 H2O --> C6H12O6

Marine Synechococcus

Marine Synechococcus: a gram negative bacteriumperforming oxygenic photosynthesis.

Hill-billy photobioreactor

200 nm

Syn9host: Synechococcus WH8109contractile tail177,300 bp225 orfs