Post on 16-Dec-2015
Photobiological Hydrogen
Production Using Bioengineered Algae
Outline
• Advantages to a Hydrogen Fuel Economy
• Green Algae
• Limitations of the Algae Cell
• Physiology and Two-Stage Photosynthesis of Production with Green Algae
• Possible Solutions to Current Limitations of Production Provided by Biotechnology
• The Future
Why Hydrogen?
• Highest energy/mass density of all known fuel types
• Produced Domestically
• Sustainable (if produced from water)
• Environmentally Friendly• Fuel Cell: No pollutants or greenhouse gases
• ICE: only (NOx)
Chlamydomonas reinhardtii
• Single-celled green Algae
• 1939: German researcher Hans Gaffron discovered hydrogen metabolism
• Hydrogenase Catalyzed reaction, active only in absence of oxygen
Production Limitations of the Algae Cell
• Low light conversion effiency (~10%)
• Oxygen production inhibits Fe-hydrogenase• Has not yet been overcome after 60 years of research
A hydrogen-producing C. reinhardtii culture.
Two Possible Production Pathways
• Photosystem II
• Oxidation of Indegenous Cellular Substrate
Hydrogenase-related electron transport pathways in green algae.
Two-stage photosynthesis Production
• Lack of Sulfur: reversible decline in rate of oxygenic photosynthesis, no affect to rate of mitochondrial respiration. Immediately elicited Production.
• Circumvents sensitivity of Fe-hydrogenase to oxygen through temporal separation of oxygen and photoproduction
Production by S deprivation Involves Coordinated Interaction Between
• Oxygenic photosynthesis: e- transported through e- transport chain to Fe-hydrogenase
• Mitochondrial respiration scavenges oxygen gen. by photosynthesis
• Endegenous substrate catabolism yields suitable substrate for oxidative phosphorylation in mitochondria
• Release of gas provides baseline levels of photosynthesis
Coordinated photosynthetic and respiratory electron transport and coupled phosphorylation during H2 production.
Regulation of Hydrogenase
• Grown under photo-autotrphopic condions algae neither consume or produce hydrogen
• Fe hydrogenase gene induced upon incubation of cells under anaerobic conditions in the dark, or S deprivation
• Results suggest oxygen is a positive suppresser of Fe hydrogenase gene expression at transcriptional level
Possible Solutions to Current Limitations
• Low light conversion efficiency: Truncate chlorophyll antenna size of PS-II using RNAi method
• Availability of reduced Ferrodoxin for Fe-Hydrogenase: Change Ferrodoxin affinity for (FNR) without affecting Fe-hydrogenase interaction
The Future
http://www.toyota.com/fuelcell/