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

1. Department of Biology Microbial energy conversion and practical application to an algal fuel cell. Peter Weigele MIT Biology and Edgerton Center Biological Energy Interest Group (BEInG) Presentation for 10.391 Sustainable Energy February 15, 2007

2. There's no place ...like home! http://visibleearth.nasa.gov/

5. The Keeling curve

6. Today’s message: Life has an incredible diversity of mechanisms for the interconversion of different forms of energy, including sunlight, inorganic and organic chemical energy. Biological productivity and energy conversion underlies fossil fuels, 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!)

7. Food and fuel subject to the same market forces? A Culinary and Cultural Staple in Crisis: Mexico Grapples With Soaring Prices for Corn -- and Tortillas By Manuel Roig-Franzia Washington Post Foreign Service Saturday, 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.” 9 x 109 by 2050

8. 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.

9. 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

11. Electrons go where they are most wanted...

12. Aerobic respiration Oxygen is a potent electron acceptor. Freely diffuses across biological membranes. Electrons can accomplish work as they traverse respiratory systems en route to oxygen.

13. Aerobic respiration: O2 as terminal electron acceptor “Bacteria are beautiful” by Diane Newman

14. Anaerobic respiration 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, electron carriers OR by using cell surface protein complexes. Other example of anaerobic respiration is fermenation (6 ATP/glucose versus 30ATP/glucose).

15. Anaerobic respiration with Iron(III) as extracellular terminal e- acceptor soluble electron carriers “Bacteria are beautiful” by Diane Newman

16. see also www.geobacter.org

17. Protein nanowires also found in gram negative aerobes, cyanobacteria, and methanogens http://www.pnas.org/cgi/doi/10.1073/pnas.0604517103

18. Schematic of a microbial fuel cell ...anode is a continually replenished electron acceptor!

19. Sediment battery: a type of microbial fuel cell

20. Bacterial biomass from electricity

21. Running a microbial fuel cell in reverse can drive otherwise thermodynamically unfavorable chemistry.

22. Summary, part I: The microbial fuel cell could be a core technology for energy conversion cellulose-derived carbohydrates energy rich wastewater organic sediments sunlight electricity microbial metabolism ex vivo protein complexes anode/cathode composition electron carriers fuel cell construction MFC electricity hydrogen alcohols methane treated water

23. Part II: Photosynthesis

26. NADPH NADP+ ADP + Pi ATP light H+ stroma light 5 3 FNR Fd F1F0 ATP- synthase 1 2 H+ cyt bf complex photo- system I (P700) photo- system II (P680) Light Harvesting Complex (LHCII) Light Harvesting Complex (LHCI) Q OEC thylakoid membrane 4 PC 2 H2O 4 H+ + O2 H+ H+ thylakoid lumen

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32. Part III: A simple, low-cost algal fuel cell for research and education

33. 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

34. Chlamydomonas rheinhardtii making colonies on solid medium

35. Photobioreactors: modular, scalable

36. Algal growth using an airlift bioreactor Airlift with Gas Dispersion Tube Gas Dispersion Tube Only

37. PVC insert to create air-lift for improved mixing

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

39. The finished recirculating pump

40. Gas managment and fuel cell Luer fittings and stopcocks fromCole-Parmer petstore 40 bucks from fuelcellstore.com

41. Bioreactor setup

42. Fuel cell under load Photobioreactor Fuel Cell Online Data Monitoring H2 e-

43. Data collection using an A/D converter Dataq model 154, ~$100, microvolt resolution

44. Experimental overview 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

45. Do other kinds of green, microalgae make H2? Chlamydomonas rheinhardtii Unknown: “WP2” Unknown: “WP1”

46. Testing different algal strains (note clumping Chlamy)

47. Algal strain choice impacts H2 production:As Indicated by Varying Voltage Output data from 10.28 Team C, 2006

48. data from 10.28 Team C, 2006

49. 10.28 Team C Sohrab Virk Asish Misra Joia Ramachandani

50. Sophmore biology students from Nashoba Regional HS Kay Leigh Kay