The humble breadcrumb could hold the key to cutting out fossil fuels from one of the chemical industry’s most widely used reactions, according to a new study.
Scientists have found a one-pot microbial formula that uses waste bread to replace fossil fuel-derived hydrogen in hydrogenation – a chemical reaction used extensively to manufacture foods, pharmaceuticals, plastics and other everyday products.
The new approach is carbon-negative and could open up new routes for bio-based manufacturing using renewable and waste-derived raw materials, researchers say.
Hydrogenation is a cornerstone of modern chemical manufacturing, but today it depends almost entirely on hydrogen gas made from fossil fuels. Both producing and using this hydrogen is highly energy-intensive, often requiring temperatures of several hundred degrees Celsius and pressures comparable to those found at the deepest parts of the ocean.
In food processing, hydrogenation is used to convert liquid vegetable oils into more stable solid fats. In industry more broadly, it is a key step in the synthesis of pharmaceuticals, fine chemicals, fuels and polymers – typically using metal catalysts such as nickel, palladium or platinum.
Scientists from the University of Edinburgh’s Wallace Lab have now shown that hydrogenation can be carried out using hydrogen gas produced naturally from living bacteria.
In the study, a common laboratory strain of E. coli was fed sugars extracted from waste bread and grown without oxygen. Under these conditions, the bacteria naturally produce hydrogen gas. When a small amount of palladium catalyst and a target chemical were added to the same reaction pot, the hydrogen generated by the microbes was sufficient to drive hydrogenation under mild, low-energy conditions.
The entire process takes place in a single sealed flask at near-room temperature, without the need for fossil fuels or externally supplied hydrogen gas.
A detailed analysis showed that the process can be carbon-negative when waste bread is used as the starting material. By avoiding fossil-derived hydrogen and diverting food waste from landfill or incineration, the system removes more greenhouse gases than it produces.
The team is planning to expand this approach to a broader array of everyday valuable products, and investigating different microbial hosts to develop strains that remove the need for a metallic catalyst.
The study, published in Nature Chemistry, was funded by UK Research and Innovation (UKRI), European Research Council (ERC), Industrial Biotechnology Innovation Centre (IBioIC) and High-Value Biorenewables Network.
Industry partners included University of Edinburgh biotechnology startup MiAlgae, sustainable feedstock manufacturer C-Source Renewables and microbiology company NCIMB Ltd, supported by Edinburgh Innovations.
Professor Stephen Wallace, Personal Chair of Chemical Biotechnology, School of Biological Sciences, University of Edinburgh, said:
Hydrogenation underpins huge parts of modern manufacturing, but it still relies almost entirely on hydrogen made from fossil fuels. What we’ve shown is that living cells can supply that hydrogen directly, using waste as a feedstock, and do so in a way that can actually be carbon-negative.
“This approach isn’t limited to food chemistry either. Hydrogenation is used across pharmaceuticals, fine chemicals and materials. Being able to run these reactions using microbial hydrogen opens up new possibilities for sustainable manufacturing at scale. ”
Dr Susan Bodie, Director of Innovation Development and Licensing at Edinburgh Innovations, said:
Professor Wallace is one of several researchers at the University of Edinburgh using innovative and sustainable engineering biology techniques to valorise waste. These techniques could help bring about a green revolution in industrial manufacture in the UK and beyond, and we would urge companies interested in working with us to get in touch.”
Douglas Martin, Founder and CEO of MiAlgae, said:
"MiAlgae is using advanced biotechnology techniques to sustainably produce Omega 3s for the aquaculture and pet feed industries. Having recently broken ground on our new plant at Grangemouth, we believe biotechnology can transform industrial processes and build a more sustainable future.”
White, M.F.M., Trotter, C.L., Steele, J.F.C. et al. Native H2 pathways enable biocompatible hydrogenation of metabolic alkenes in bacteria. Nat. Chem. (2026). https://doi.org/10.1038/s41557-025-02052-y
