In a collaboration led by Professor Neil Thomas, we are working to develop new ways of carrying out biocatalytic reactions in alternative solvents. Our work involves two different strategies:
The use of continuous fixed bed reactors to carry out enzymatic reactions in supercritical CO2. The enzymes are immobilized either by using commercially available lipases (e.g. Novozym 435) or by forming cross-linked enzyme aggregates, CLEAs. Publications include “Continuous Kinetic Resolution Catalysed by Cross Linked Enzyme Aggregates, “CLEAs”, in Supercritical CO2” (H. R. Hobbs, B. Kondor, P. Stephenson, R. A. Sheldon, N. R. Thomas and M. Poliakoff) Green Chem. (2006) 8, 816-821
The application of Hydrophobic Ion Pairing to solubilize biomolecules in supercritical CO2 and fluorous solvents, by pairing cationic sites on the surface of the biomolecule with fluorinated cationic surfactants to form a soluble neutral complex. These complexes can form clear “solutions” in supercritical CO2 as shown by this animation and powerpoint presentation (click OPEN for full functionality). Dynamic light scattering shows that the biomolecules are present as individual molecules or very small aggregates in fluorous solvents. High pressure DLS in collaboration with Professor KP Johnston’s group in Texas suggests that larger aggregates may be present in supercritical CO2. Publications include: “Stable Colloidal Dispersions of a Lipase-Perfluoropolyether Complex in Liquid and Supercritical Carbon Dioxide” (Stephanie S. Adkins, Helen R. Hobbs, Karima Benaissi, Keith P. Johnston, Martyn Poliakoff, and Neil R. Thomas) J. Phys. Chem. B, 112 (15), 4760-4769, 2008. “Homogeneous Biocatalysis in both Fluorous Biphasic and Supercritical Carbon Dioxide Systems” (H. R. Hobbs, H. M. Kirke, M. Poliakoff and N. R. Thomas) Angew. Chem. Intl Ed. (2007) 46, 7860-7863. "Solubilisation of α-chymotrypsin by hydrophobic ion pairing in fluorous systems and supercritical carbon dioxide and demonstration of efficient enzyme recycling" (K. Benaissi, M. Poliakoff and N. R. Thomas) Green Chem. (2010)
This work has been supported by BBSRC, EPSRC, DSM and the EU Marie Curie Programme.