Mining natural microbial diversity for optimised biohybrid scaffolds.

Global warming caused by greenhouse gases like CO2 is a major global concern. Understanding the complex natural cycling of greenhouse gases is crucial to address the urgent climate crisis. The cycling of key greenhouse gases, like CO2, involves microorganisms that fix CO2 and release methane.

Some microorganisms also utilise intermediates like carbon monoxide (CO) and dihydrogen (H2) in their metabolism. The metabolic pathways of these microorganisms involve specialised gas-processing enzymes, which are key to understand how greenhouse gases can be fixed from the atmosphere, and directly related to biogeochemical cycles, global warming, and climate change.

This project aims to develop new biohybrid catalysts by utilising biological scaffolds to host or bind synthetic catalysts. Biohybrid catalysts hold a lot of potential to fix greenhouse gases from the atmosphere and for carbon capture and storage (CCS). They are sustainable, as they are biodegradable and produced from naturally abundant materials.

Biohybrid catalysts combine the advantages of synthetic chemistry with the benefits of natural enzymes (specificity/selectivity). However, biohybrid catalysts based on protein scaffolds from 'regular' organisms are generally restricted to ambient conditions, limiting their scope for application in biotechnology.

Extremophiles are organisms that live under extreme environments, such as under high pressures and extremes of temperature and pH. Evolution of organisms under extreme conditions has optimised their enzymes for exquisite performance under harsh conditions. This project aims to make use of the unique properties of extremophiles by mining their genomes in search of ideal scaffolds for synthetic catalysts to build biohybrid catalysts that can work under non-ambient conditions.

This project will encompass three main stages. Stage 1 will focus on searching for (i) small metalloproteins from extremophiles including enzymes active for CO2 reduction and/or H2 conversion and (ii) small proteins like ferredoxins and cytochromes. In Stage 2, the identified enzymes/proteins will be produced and characterised to test their stability under extreme conditions.

In Stage 3, the produced enzymes will be tested as candidates for binding synthetic catalysts. Overall, this project will develop new approaches for environmental biotechnology to fix greenhouse gases from the atmosphere and for CCS by building biohybrid catalysts using biological scaffolds from extremophiles.

Methodology:

The research plan breaks down as follows: 1) Analysis of databases (e.g. metagenomic databases) will be done to identify homologues of well-known hydrogenases (enzyme that catalyse H2 conversion in nature), CO dehydrogenases (enzyme that catalyse the CO2/CO interconversion in nature), as well as ferredoxins and cytochromes that are present in extremophiles. 2) The organisms of interests will be obtained and cultured in the lab to purify the enzymes. 3) In parallel with the step 2, the enzymes will be produced heterologously (e.g. inside E. coli or other hosts). 4) The structure/function of the enzymes will be studied via an integrated approach combining electrochemical, spectroscopic, structural and computational methods. 5) The produced enzymes will be tested as candidates for binding/hosting synthetic catalysts and the reactivity of the biohybrid catalysts will be explored.