Modified enzyme could make bioprocessing zippier

Researchers have devised a way to break down plant-based biomass faster than before, potentially enhancing the efficiency of industrial bioprocessing—the conversion of natural materials into chemicals, fuels, and polymers.

β-glucosidase converts cellulose and other complex carbohydrates in biomass to glucose, a basic feedstock suitable for further processing into value-added compounds like ethanol. But β-glucosidase doesn’t work in ionic liquids—organic salts that melt below 100 °C or so. These liquids readily solubilize biopolymers and other substrates that are difficult to process in conventional solvents. And the enzyme doesn’t work well at temperatures above about 70 °C, meaning higher temperatures can’t speed up the cellulose-to-glucose reaction.

Jason P. Hallett and coworkers at Imperial College London have now modified the enzyme in two ways: First, they coupled N,N′-bis(2-amino­ethyl)-1,3-propanediamine to aspartate and glutamate residues on its surface to make it cationic, and then they conjugated a surfactant, glycolic acid ethoxylate lauryl ether, to the protein (Nat. Chem. 2018, DOI: 10.1038/s41557-018-0088-6).

With the modifications, the enzyme maintains its native structure, is soluble in ionic liquids, and works at temperatures up to 137 °C. In an ionic liquid at 110 °C, the enzyme’s catalytic activity is 30 times as fast as that of the native enzyme at conventional temperatures in water.

Hallett and coworkers note that the results demonstrate how surface and solvent modifications can work together to intensify the catalytic prowess of enzymes. The approach, they write in the paper, is “a key step towards the full-scale deployment of industrial biocatalysis.”