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.
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