Hydrogen from Algae Nanotechnology Solutions

Foothill College

Bio-Nano-Info Program

Energy from the Early Earth

Energy Metabolism

Hydrogen Metabolism

H2S 2H + S H2O H + OH H2 2 H + 2e-

In photosynthesis (simplified):

H20 H + OH + 2e-

2H + CO2 CH2O OH + OH H2O + O 2O + 2e- O2

Life on Earth

Timeline for development of the major life forms.

From a course site by Robert Huskey, U. Virginia

Hydrogenase

• Biological cleavage of H2 is a common metabolic process in prokaryotes and lower eukaryotes and is catalyzed by two major classes of enzymes the [NiFe]- and the [Fe]-hydrogenases.

• Three distinct [NiFe]-hydrogenases of Ralstonia eutropha (formerly Alcaligenes eutrophus) are in the center of this project, the regulatory (RH), the NAD-linked (SH) and the membrane-bound (MBH) hydrogenase

NiFe and Fe Hydrogenase

Algae Hydrogenase Proteins

Fossilized Blue Green Algae

These filaments are believed to be the fossilized imprints of blue-green algae, one of the earliest life forms. They occur in the Bitter Springs Formation in Australia and are about 850 million years old. 

Rise of Atmospheric O2

Photosynthetic Reactions

Photosynthetic Reaction Center

1PRC

Green Algae at Work Making H2

Algal cell suspension / cells

Thylakoid membrane

In Vitro Photo-Production of H2

Yellow arrow marks insertion of hydrogenase promoter. Right side exp. optimized for continuous H2 production.

Production of H2 From Algae

http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/iic2_lee.pdf

H2 Energy Calculations

Assumptions were made that 10 micro mole of H2 can be produced per hour (roughly 50% of peak maximum but extended for an hour) per mg of chlorophyll. Additionally, a density of 10% of the top 1 cm (or 100% of top mm) of the system would be populated by chlorophyll, for a density of 1 mg chlorophyll per square cm of collector. This leads to 10,000 cm multiplied by 10 mg chlorophyll per centimeter for a total of 100,000 mg chlorophyll.  Multiplying 100,000 mg chlorophyll by 10 micromole H2 generated per hour per mg chlorophyll yield 1 mole of hydrogen gas per square meter per hour.  Combusting one mole of H2 with one half mole of oxygen (H2 + ½ O2 H2O) yields 286 KJoules or 68 Kcal. Using any of the following conversions yields KWatt hours or watts from this reaction: 1 calorie = 4.184 Joules1 calorie = 0.0011622 KwHr1 Joule = 0.0002778 Watt hours1 K Joule = 0.2778 watts 286 KJoules X 0.2778 Watts / KJoules = 79 Watts 68,355 calories X 0.0011622 KwHr per calories = 79 KwHr On first pass, it appears that 1 square meter of hydrogen producing algae (modified for continuous hydrogen production) yields about 79 watts, or enough to run a 75 watt light bulb at full power.

ORNL Project Road Map

• Year 1- Design and construction of DNA sequence coding for polypeptide proton channel

• Year 2 - Genetic transfer of hydrogenase promoter-linked polypeptide proton-channel DNA into algal strain DS521

• Year 3 - Characterization and optimization of the polypeptide proton-channel gene expression

• Year 4 - Demonstration of efficient and robust production of H2 in designer alga (ready for next phase - scale-up and commercialization)

Genetic / Biochemical Engineered H2 Bacterium

• Sequence coding for polypeptide proton channel – create gene for proton pump

• Genetic transfer of hydrogenase promoter-linked polypeptide proton-channel DNA into algal genome – express pump with H2

• Characterization and optimization of the polypeptide proton-channel gene expression

Proposed Engineered H2 Bacterium

http://gcep.stanford.edu/pdfs/tr_hydrogen_prod_utilization.pdf

Promoter Spliced into Operons

Polypeptide Proton Channel

• Protons that build up from cleavage of H2O into H atoms repress hydrogenase reaction

• Need to pump hydrogen atoms away from the photosynthetic reaction core, and into storage

• Hydrogen storage in a carbon nanotube can be the first stage in a nano-structure fuel cell– Platinum doped carbon nanotubes might be an

integrated device: storage, fuel cell, and battery

Membrane Bound Protein Pumps

Proton and ion pumps consumea lot of cellular energy

Nano-channels could be useful

Proteins in Plasma Membrane

Transmembrane DomainsAlpha Helix Structure

Transmembrane DomainsBeta Sheet Structure

Nano Solutions – Hydrogen Storage

Carbon Nanotube Structures

Nanotubes / Nanohorns

The electrical properties of nanotubes / nanohorns can change, depending on their molecular structure. The "armchair" type has the characteristics of a metal; the "zigzag" type has properties that change depending on the tube diameter—a third have the characteristics of a metal and the rest those of a semiconductor; the "spiral" type has the characteristics of a semiconductor.

Nanotube Properties

http://nanotech-now.com/nanotube-buckyball-sites.htm

Nanotube ‘Semi’ Structures

Hydrogen Fuel Cell Basics

http://micro.magnet.fsu.edu/primer/java/fuelcell/

   

Hydrogen Fuel Cell Diagrams

Schematic representation of acomposite electrode for low temperature fuel cells

Schematic representation of themembrane electrode assembly

http://www1.physik.tu-muenchen.de/lehrstuehle/E19/research/pefc.html

Electrochemical Probes with Nanometer Dimensions

Photovoltaic Cells for Solar Capture

H2 Production might also be used in Space

Summary

• Hydrogen metabolism is ancient, and highly conserved in hydrogenase / photosynthesis

• With genetic / biochemical engineering, algae can make H2 in significant amounts

• Capturing and wicking of H2 into a carbon nanotube fuel cell / battery is very feasible

• A 1 sq. meter collector could power a 500 watt household with ~ 10X technology gain