Published in Nature Communications, the study shows how bacterial protein ‘cages’ can be reprogrammed as a nanobioreactor for hydrogen production. The carboxysome is a specialised bacterial organelle that encapsulates the CO2-fixing enzyme Rubisco into a virus-like protein shell.
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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.
Researchers installed specific genetic elements into the industrial bacterium E. coli to produce empty carboxysome shells, identifying a small ‘linker’ (called an encapsulation peptide) capable of directing external proteins into the shell. The team developed methods to incorporate catalytically active hydrogenases (enzymes that catalyse the generation and conversion of hydrogen) into the empty shell, and through testing the hydrogen-production activities of the bacterial cells and the biochemically isolated nanobioreactors, found that the nanobioreactor achieved a 550 per cent improvement in hydrogen-production efficiency.
Project lead Luning Liu, Professor of Microbial Bioenergetics and Bioengineering at the Institute of Systems, Molecular and Integrative Biology, said that their newly designed bioreactor is “ideal for oxygen-sensitive enzymes” and marks an important step toward being able to develop and produce a bio-factory for hydrogen production.
“The next step for our research is answering how we can further stabilise the encapsulation system and improve yields,” Professor Liu said in a statement. “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, added: "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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