Replicating photosynthesis to produce sustainable fuel

Researchers from The Australian National University (ANU) have successfully replicated one of the crucial steps in photosynthesis, opening the way for biological systems powered by sunlight which could manufacture hydrogen as a fuel. Their research has been published in the journal BBA Bioenergetics.

Hydrogen offers potential as a zero-carbon replacement for petroleum products and is already used for launching spacecraft. However, until recently, the way that plants produce hydrogen by splitting water has been poorly understood.

The team modified a ubiquitous protein, ferritin, which is present in almost all living organisms. Ferritin’s usual role is to store iron, but the team removed the iron and replaced it with manganese to closely resemble the water splitting site in photosynthesis.

The protein also binds a haem group, which the researchers replaced with a light-sensitive pigment, zinc chlorin. When exposed to light, the modified protein displayed the electrical heartbeat (charge transfer) that is the key to photosynthesis.

Dr Kastoori Hingorani and Professor Ron Pace. Image: Stuart Hay, ANU.

Dr Kastoori Hingorani, from the ARC Centre of Excellence for Translational Photosynthesis in the ANU Research School of Biology, noted that as the system uses a naturally occurring protein, and does not need batteries or expensive metals, it could be affordable in developing countries. Co-researcher Professor Ron Pace added that the research marks “the first time we have replicated the primary capture of energy from sunlight” and could be the beginning of “a whole suite of possibilities, such as creating a highly efficient fuel or … trapping atmospheric carbon”.

Manufacturing hydrogen fuel from artificial photosynthesis could transform the economy, said Professor Pace, who noted, “That carbon-free cycle is essentially indefinitely sustainable.

“Sunlight is extraordinarily abundant, water is everywhere … And at the end of the usage cycle it goes back to water,” he said.

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