A mutated lipase from Yarrowia lipolytica was used in aqueous phase/scCO2 two-phase systems to perform the enzymatic resolution of (R, S) 2-bromophenyl acetic octyl ester. A solution of phosphate salt (1000 mmol/L) was added to buffer the aqueous phase in contact with CO2 and resulting pH values around 6 were measured in a high pressure cell using a solvatochromic probe.
Thus, an acceptable conversion rate and good enantioselectivity could be obtained but kinetics were shown to remain slower compared to an aqueous phase/decane two-phase system. Moreover, increasing pressure was shown to further slowdown the kinetics.
This was hypothesized to be related to the mechanism of opening of the active site of the lipase which requires interfacial contact with a hydrophobic solvent phase. This condition is suspected not to be met in the case of scCO2 in contact with an aqueous phase because the amount of water dissolved in the supercritical phase diminishes its hydrophobicity. © 2016 Elsevier B.V.