Activity, stability and enantioselectivity of lipase-coated microcrystals of inorganic salts in organic solvents

Abstract

Lipase-coated microcrystals of inorganic salts were prepared by dissolving enzymes in buffers and then mixing with 3 volumes of saturated salt solutions followed by drop-wise addition into polar precipitating organic solvents. The Mucor javanicus lipase-coated microcrystals did not show any activity for esterification of lauric acid with 1-propanol in isooctane when NaCl and Na₂SO₄ were used as the salts but showed much higher activity than the enzyme powder when KCl (10.0 times) and K₂SO₄ (5.8 times) were used as the salts and precipitated in 1-propanol. Acetonitrile was found to be the best precipitating solvent for preparing M. javanicus lipase-coated microcrystals, with enzyme activities 26.2 and 22.4 times higher than that of the enzyme powder when KCl and K₂SO₄ were used as precipitating salts, respectively. The presence of water in the precipitating solvents markedly decreased the enzyme activity. The M. javanicus lipase-coated microcrystals prepared using K₂SO₄ as the salt and acetonitrile as the precipitating solvent was as active at 80°C as at 40°C. No significant improvement in enantioselectivity of Candida rugosa lipase-coated microcrystals was observed for transesterification of 1-phenylethanol with vinyl acetate in hexane when the microcrystals were prepared by dissolving the enzymes in salt solutions containing 25% (v/v) of acetone or 2-propanol before precipitating in polar solvents.

• lipase
• protein-coated microcrystal
• activity
• enantioselectivity
• organic solvent