UK researchers unlock new possibilities for developing clean bioenergy using bacterial protein ‘cages’

Researchers at the University of Liverpool in the UK have unlocked new possibilities for the future development of sustainable, clean bioenergy.

The study, published in Nature Communications, demonstrates how bacterial protein ‘cages’ can be re-programmes as nanoscale bioreactors for the production of hydrogen.

According to the university, the carboxysome is a specialised bacterial organelle that encapsulates the essential carbon dioxide-fixing enzyme Rubisco into a virus-like protein shell. The naturally-designed architecture, semi-permeability, and catalytic improvement of carboxysomes have inspired the rational design and engineering of new nanomaterials to incorporate different enzymes into the shell for enhanced catalytic performance.

Project lead Professor Luning Liu, Professor of Microbial Bioenergetics and Bioengineering at the Institute of Systems, Molecular and Integrative Biology, said: “Our newly designed bioreactor is ideal for oxygen-sensitive enzymes, and marks an important step towards being able to develop and produce a bio-factory for hydrogen production.”

The first step in the study involved researchers installing specific genetic elements into the industrial bacterium E. coli to produce empty carboxysome shells. The researchers further identified a small ‘linker’ – called an encapsulation peptide – capable of directing external proteins into the shell.

The extreme oxygen-sensitive character of hydrogenases (enzymes that catalyse the generation and conversion of hydrogen) is a long-standing issue for hydrogen production in bacteria, so the team developed methods to incorporate catalytically-active hydrogenases into the empty shell.

“The next step in our research is answering how we can further stabilise the encapsulation system and improve yields,” added Professor Liu.

“We are also excited that this technical platform opens the door for us, in future studies, to create a diverse range of synthetic factories to encase various enzymes and molecules for customised functions.”

First author, PhD student Tianpei Li, said: “Due to climate change, there is a pressing need to reduce the emission of carbon dioxide from burning fossil fuels.

“Our study paves the way for engineering carboxysome shell-based nanoreactors to recruit specific enzymes and opens the door for new possibilities for developing sustainable, clean bioenergy.”

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