Immobilization and enantioselectivity of Bacillus pumilus lipase in ionic liquids

Lipases are excellent catalysts for industrial applications ranging from laundry detergents to fine chemicals synthesis. Bacillus pumilus lipase A (BplA) belongs to a subfamily of small hydrolases displaying a remarkable enantioselectivity in hydrolytic reactions. Recombinant BplA was immobilized in silica gel and its enantioselectivity was evaluated. BplA displays a notorious enantioselectivity towards the R enantiomer of 1-phenylethyl acetate in hydrolytic reactions. In agreement with this hydrolytic enantioselectivity, BplA immobilized in silica gel is enantioselective towards the R enantiomer of 1-phenylethanol for the synthesis of its hexanoic acid ester in n-hexane as solvent. In contrast, isoinversion was observed in the ionic liquids 1-ethyl-3-methylimidazolium methanesulfonate ([Emim][CH3SO3]) or 1-ethyl-3-methylimidazolium methylsulfate ([Emim][EtSO4]). At temperatures from 25 to 35 °C, BplA produces only the (R)-enantiomer of the ester, while at temperatures from 15 to 20 °C the enantioselectivity is inverted towards the corresponding (S)-enantiomer.