New enzyme boost could hasten biofuel production

By Imperial College London | July 05, 2018

Scientists at Imperial College London have enhanced the process of using biology to make products such as fuels, plastics, medicines, and cosmetics.

This could lead to cheaper and more environmentally friendly biofuel production and more efficient plastic recycling.

Bioprocessing, which uses living cells or their components to make products like biofuels, plastics, medicines, and cosmetics, is time consuming and expensive.

Now, Imperial scientists say they can break down plant-based biomass 30 times faster than currently possible. The findings are published in Nature Chemistry.

If this new technique is taken up on a large scale, fuel-related carbon emissions could fall by 80-100 per cent.

Alex Brogan, of Imperial College London’s Department of Chemical Engineering, and colleagues modified the glucosidase enzyme, which helps break down complex carbohydrates in biomass, like cellulose from plant cells, into its basic units, glucose. The glucose can then be fermented to make ethanol, a form of biofuel.

Biofuels are fuels made from living matter like plants, otherwise called biomass. They emit far less carbon dioxide than fossil fuels, so are far better for the environment.

Releasing glucose from cellulose is currently the most expensive and time consuming part of the process. This is partly because enzymes typically stop working at temperatures higher than 70 degrees Celsius and when in industrial solvents like ionic liquids.

However, if the enzyme could work in higher temperatures and ionic liquids, the conditions would hasten the process.


Breaking barriers

To make glucosidase more robust, Brogan and colleagues altered its chemical structure to let it withstand heat of up to 137 degrees Celsius. The alteration also meant they could use the enzyme in ionic liquids instead of the usual water, and that they could use only one enzyme instead of three.

They found that the combined effect of heat resistance and solubility in ionic liquids increased the glucose output 30-fold.

If this new technique is taken up on a large scale, fuel-related carbon emissions could fall by 80-100 per cent.

Lead author Brogan said, “We’ve made bioprocessing faster, which will require less equipment and will reduce carbon footprint. One major advantage of this will be increased biofuel production—potentially helping biofuels become more widespread as a result.”

Senior author Jason Hallett, also from Imperial’s Department of Chemical Engineering, said, “Using biofuels made from corn starch, trees and other plant matter for vehicles and even electricity generation could massively reduce carbon emissions.”

The alteration could be applied to a wide variety of enzymes, for a wide range of applications, such as making fuels from waste and recycling plastics, and can make bioprocessing more efficient.

This research was funded by the Engineering and Physical Sciences Research Council (EPSRC).

Diamond Light Source, which is funded by the Science and Technology Facilities Council (STFC) and the Wellcome Trust, provided access to the B23 and I22 synchrotron beamlines where researchers measured enzyme thermal stability and structure.

Non-aqueous homogenous biocatalytic conversion of polysaccharides in ionic liquids using chemically modified glucosidase” by Alex P. S. Brogan, Liem Bui-Le and Jason P. Hallett, published 15 June 2018 in Nature Chemistry.