Ionic liquids: Enzymatic cellulose processing

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  • Published: Dec 1, 2015
  • Author: David Bradley
  • Channels: NMR Knowledge Base
thumbnail image: Ionic liquids: Enzymatic cellulose processing

Ionic alternative

Ionic liquid with unique properties, Umeå University. Credit: Johan Gunséus

The promise of room temperature ionic liquids (RTILs) as alternatives to toxic and inflammable volatile organic solvents for green chemistry has been on the boil for at least a couple of decades. Now, team has found that enzymatic activity can be sustained in processing cellulose, from wood, for conversion of this raw material into other useful compounds.

RTILs are unusual materials in that unlike most ionic compounds they have very low melting points close to room temperature. This is a product of the high lattice energy required of the bulky ions involved to form crystals at low temperature. Being ionic, however, these liquids can dissolve a wide range of materials while their negligible vapour pressure makes them less noxious than their organic counterparts. As such, there have been great efforts to use ionic liquids to replace organic solvents for the sake of reduced environmental impact of chemical processes.

Now, two research teams at Umeå University, Sweden, have shown that switchable ionic liquids can sustain enzymatic activity, thus paving the way for the enzymatic refinement of cellulose to useful molecules and industrial products. The team outlines details of the switchable ionic liquid (SIL) formed by monoethanol amine (MEA) and 1,8-diazabicyclo-[5.4.0]-undec-7-ene (DBU) with sulfur dioxide as the coupling media in the journal ChemSusChem.

Enzymatic breakthrough

In their earlier work, the research group of Jyri-Pekka Mikkolas discovered that hemicellulose, cellulose and lignin could be selectively separated and dissolved using a new type of so-called switchable ionic liquid. Collaborating with the team of Magnus Wolf-Watz, Mikkolas and colleagues then went on to show that enzymes can function in this particular ionic liquid. This is quite a bizarre discovery given that enzymes evolved over millions of years to function in a largely aqueous, physiological environment.

"Our discovery is a scientific breakthrough!" enthuses chemist Wolf-Watz. "This is the launch that enables us to extract small key molecules directly from wood. There are many applications not in the least in the production of ethanol as fuel but also a number of other things," he adds. The team used nuclear magnetic resonance spectroscopy to study the processes and products involved. Crucially, they developed a new approach to monitor enzymatic activity, in this work of adenylate kinase, using real time measurements and phosphorus-31 NMR spectroscopy. The NMR internationally renowned infrastructure at Umeå is funded by the Kempe and Wallenberg Foundations.

Taking biorefining wood up a notch

"This development will be of major importance to the measurement of enzymatic catalysis in complex solutions and preparations, and the method is already being used in new projects," explains fellow chemist Mikkolas. The research team as a whole has scientists from both biochemistry and technical chemistry and Mikkolas' research team is a part of Bio4Energy's research environment that aims to take Swedish biorefinery research to a new level.

Related Links

ChemSusChem 2015, online: "Realtime 31P NMR Investigation on the Catalytic Behavior of the Enzyme Adenylate kinase in the Matrix of a Switchable Ionic Liquid"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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