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Grantee Research Project Results

NCER Grantee Research Project Results

Developing a Metabolic Switch for Photobiological Hydrogen Production

EPA Grant Number: FP917164
Title: Developing a Metabolic Switch for Photobiological Hydrogen Production
Investigators: Luterra, Markael Daniel
Institution: Oregon State University
EPA Project Officer: Zambrana, Jose
Project Period: September 1, 2010 through August 31, 2013
Project Amount: $111,000
RFA: STAR Graduate Fellowships (2010)
Research Category: Academic Fellowships , Fellowship - Science & Technology for Sustainability: Energy

Description:

Objective:

Photobiological hydrogen production offers the promise of efficient, low-cost, and pollution-free solar energy conversion. Certain algae and cyanobacteria contain all of the required enzymes for this process, but several major challenges remain to be addressed, including redirection of electron flow to the hydrogenase enzyme. In this project I aim to increase hydrogen production from the cyanobacterium Synechocystis sp. PCC 6803 by downregulating electron flow through two alternative pathways and increasing hydrogenase expression.

Synopsis
Solar energy has strong potential to replace fossil fuels, but at present it is impossible to efficiently convert sunlight to liquid or gaseous fuel. Cyanobacteria can use sunlight to generate hydrogen gas, and the theoretical efficiency (around 10-15%) rivals that of PV panels. For efficient hydrogen production, the flow of energized electrons through competing metabolic pathways must be reduced. In this project I will downregulate two of these pathways, hopefully increasing hydrogen yields.

Approach:

I will replace the native promoter sequences of two genes essential for cyclic electron flow and electron flow to the Calvin cycle with a promoter that can be induced or repressed. I will then use microarrays to identify genes that are strongly upregulated when expression of these two genes is repressed. After confirming substantial upregulation with qRT-PCR, I will insert the promoter from an upregulated gene in place of the native hydrogenase operon promoter to obtain increased hydrogenase expression.

Expected Results:

With downregulation of cyclic electron flow and electron flow to the Calvin cycle and increased hydrogenase expression, I expect to see dramatically increased hydrogen production under enforced anaerobic conditions and during dark-to-light transitions. While efficient hydrogen production under full light will not be achieved until oxygen tolerance of the hydrogenase is improved, the metabolic switch developed in this project will greatly enhance hydrogen production once that goal is reached. The two-way genetic switch developed here will be widely applicable to other cyanobacterial bioenergy projects, such as lipid accumulation for biodiesel, sunlight-to-ethanol, or butanol production.

Potential to Further Environmental/Human Health Protection
Climate change, linked primarily to carbon dioxide emissions, is the largest environmental challenge facing humanity in this century. Current-generation biofuels have sunlight-to-energy conversion efficiencies of 0.1-0.2 percent, too low to meet our transportation fuel needs from available land even if substantial conservation measures are enacted. Photobiological hydrogen offers the potential for sunlight-to-fuel efficiencies exceeding 10 percent, which would greatly enhance our ability to meet our energy needs while eliminating carbon emissions.

Supplemental Keywords:

hydrogen, cyanobacteria, microalgae, solar, bioenergy,

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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