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Scientists create 'nano-reactor' for producing hydrogen biofuel

05 January 2016

A combination of bacterial genes and virus shell creates a highly efficient, renewable material that can be used to generate power from water.

Artist's impression of P22-Hyd, a new biomaterial created by encapsulating a hydrogen-producing enzyme within a virus shell (image: Indiana University)

Scientists at Indiana University (IU) have created a highly efficient biomaterial that catalyses the formation of hydrogen - one half of the 'holy grail' of splitting water to make hydrogen and oxygen.

A modified enzyme that gains strength from being protected within the protein shell - or 'capsid' - of a bacterial virus, this new material is 150 times more efficient than the unaltered form of the enzyme.

The process of creating the material was recently reported in the journal, Nature Chemistry.

"Essentially, we've taken a virus's ability to self-assemble myriad genetic building blocks and incorporated a very fragile and sensitive enzyme with the remarkable property of taking in protons and spitting out hydrogen gas," says IU's Professor Trevor Douglas who led the study. "The end result is a virus-like particle that behaves the same as a highly sophisticated material that catalyses the production of hydrogen."

The genetic material used to create the enzyme, hydrogenase, is produced by two genes from the common bacteria Escherichia coli (E. coli), inserted inside the protective capsid using methods previously developed by IU scientists. The genes, hyaA and hyaB, are two genes in E. coli that encode key sub-units of the hydrogenase enzyme. The capsid comes from the bacterial virus known as bacteriophage P22.

The resulting biomaterial, called 'P22-Hyd', is not only more efficient than the unaltered enzyme but is also produced via a simple fermentation process at room temperature.

Moreover, the material is potentially far less expensive and more environmentally friendly to produce than other materials currently used to create fuel cells. The costly and rare metal platinum, for example, is commonly used to catalyse hydrogen as fuel for cars.

"This material is comparable to platinum, except it's truly renewable," says Professor Douglas. "You don't need to mine it; you can create it at room temperature on a massive scale using fermentation technology; it's biodegradable. It's a very green process to make a very high-end sustainable material."

In addition, P22-Hyd breaks the chemical bonds of water to create hydrogen and also works in reverse to recombine hydrogen and oxygen to generate power. The reaction runs both ways - it can be used either as a hydrogen production catalyst or as a fuel cell catalyst.

Beyond the new study, Douglas and his colleagues continue to craft P22-Hyd into an ideal ingredient for hydrogen power by investigating ways to activate a catalytic reaction with sunlight, as opposed to introducing elections using laboratory methods.

"Incorporating this material into a solar-powered system is the next step," he says.

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