Hydrogen-Producing Cyanobacteria
A team of Savannah River National Laboratory (SRNL) researchers is studying how the relationships between blue-green algae and its environment, particularly nutrients and other bacteria, affect its ability to produce hydrogen that could be collected and used for the nation’s energy needs. Results indicate that a carbon “boost” may increase the hydrogen production capacity of many strains.
One of the keys to making a hydrogen-powered future feasible is developing environmentally and economically sound methods of producing large quantities of hydrogen. Biological hydrogen production by cyanobacteria, also called blue-green algae, is a highly attractive option because:
- It uses a renewable resource requiring only water, sunlight, air, and trace mineral salts.
- It does not use or produce hazardous materials.
- It is carbon-neutral or even carbon–negative process (absorbing carbon, rather than producing it).
“It is known that many thousands, or even millions, of naturally occurring bacteria species have the ability to use sunlight to produce hydrogen,” says Chris Yeager, one of the researchers on the project, “but only a handful of strains have been studied.” From a biotechnological perspective, he says it makes sense to explore (and potentially harness) the untapped diversity of H2-producing capabilities that have been naturally evolving for billions of years.
To advance the utility of these microorganisms for energy production, SRNL is conducting studies to 1) assess the overall physiological effects that bacterial associates and environmental factors have on cultures of hydrogen-producing cyanobacteria, and 2) characterize the combined effect of glucose and light on hydrogen-producing cyanobacteria.
Cyanobacteria are almost always closely associated with other bacteria. Indeed, many strains of cyanobacteria cannot be isolated and grown without their bacterial associates. Still, very little detail is known about the interactions between the cyanobacteria and their commonly associated bacteria, especially how those interactions could affect the ability to produce hydrogen. SRNL screened ~75 bacteria for their ability to enhance or inhibit cyanobacteial growth, and found that several impart a slight growth advantage.
To learn more about the effect of light and carbon source on hydrogen production, SRNL examined 10-12 diverse cyanobacterial strains and found that glucose stimulated hydrogen production rates and yield in the majority of strains – as much as a 40-fold increase in yields in some strains. Other carbon sources (or “carbon boosts”) were also found to increase cyanobacterial hydrogen production. These results support the idea that organic rich waste streams from certain industrial processes could be used to stimulate photobiological hydrogen production.
In many strains, glucose-dependent hydrogen production rates and yield were not greatly stimulated by increases in light intensity. This research counters the commonly held belief that the techno-economic feasibility of cyanobacterial hydrogen production depends solely on light conversion efficiency, and points toward the utilization of “carbon boosts” to increase production.
