Advancing Biocatalysis: Using Siloxanes to Solubilize and Stabilize Enzymes in Organic Solvents

Biocatalysis presents an interesting opportunity for addressing the need for sustainability in chemical processes, especially as a means of supplanting catalysts based on nonrenewable metals. However, a significant challenge facing this strategy is the propensity for biological molecules to function optimally in aqueous environments while many chemical transformations occur in organic solvents, an environment that is typically antithetical to the functioning of enzymes. To address this challenge, we have modified proteins with siloxane oligomers in an effort to generate biocatalytic systems that can be used in homogeneous reaction systems rather than as heterogeneous catalysts where the biocatalyst is immobilized on a solid support. The siloxane-modified proteins displayed activity and stability in organic solvents that is comparable to that observed with unmodified proteins in aqueous environments and demonstrated excellent solubility in organic solvents. Modification of the proteins was a straightforward process that demonstrated a high level of efficiency. The covalent modification of human serum albumin (HSA) and trypsin with siloxanes was examined using matrix assisted laser desorption ionisation time of flight mass spectrometry (MALDI-TOF-MS) and the Michaelis-Menton activity of the enzyme was studied using standard assays.