Enzyme Catalysis Extended: Lipase-Catalysed Synthesis at ESS

After applying lactate dehydrogenase catalysis to the synthesis of perdeuterated enantiopure lactic acid, the ESS deuteration lab is now extending its use of enzyme catalysis to the lipase class of enzymes. The natural function of these enzymes is to hydrolyse ester bonds of triglycerides, releasing free fatty acids, under aqueous conditions. Lipases are also remarkably stable in organic solvents, and so can be encouraged to perform the reverse esterification reaction under water-free or water-limited conditions (Scheme 1).

lipase equilibrium reaction
Scheme 1. Lipase-catalysed hydrolysis/formation of esters.

Lipases are already used extensively in synthetic chemistry, so much so that many of them are commercially available in immobilised form. The ESS lab has recently procured a rotating bed reactor (RBR – Figure 1), and some lipases immobilised on various solid supports, contained within cartridges designed to be used in combination with the RBR. This equipment should allow the use of lipases to perform efficient synthetic transformations of deuterated molecules using immobilised enzymes.

RBR
Figure 1. The SpinChem® rotating bed reactor (RBR) system used for immobilised lipase reaction in the ESS deuteration laboratory.

Initial work has begun with a simple, unlabelled esterification system (Scheme 2). The reaction can easily be monitored by GC-FID, allowing for analysis of reaction progress and kinetics (Figure 2).

lauric acid esterification
Scheme 2. Lauric acid esterification catalysed by immobilised CalB lipase.
GC trace lauric acid est
Figure 2. Lauric acid esterification can be monitored by GC-FID, comparing the peak areas of the acid and ester in hexane.

Work will soon continue with more complex, deuterium-labelled systems to produce deuterated materials of use in neutron scattering experiments.

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