Enzymatic synthesis of banana flavour (isoamyl acetate) by Bacillus licheniformis S-86 esterase

New carboxylesterase from organic-solvent-tolerant Bacillus licheniformis S-86 strain was characterized. The enzyme named as type II esterase showed an optimal activity in the temperature range 60-65 degrees C and pH 8.0. The enzyme was moderatly thermostable (half-life of 1 h at 50 degrees C), but remarkable stable at extremely alkaline PH. retaining 100% of its activity at pH 10.0-11.0. Furthermore, the esterase showed high stability in detergents (86% residual activity in 10% SDS), and also 0.1% ionic and non-ionic detergents are inducers of enzyme activity. PMSF, a serine protease inhibitor, did not show any effect on the activity, The immobilized type II esterase was able to synthesize isoamyl acetate from isoamyl alcohol and p-nitrophenyl acetate (acyl donor) in n-hexane. The resulting ester yield (42.8%), obtained at a low temperature (28 degrees C) and with a very low amount of enzyme (4.6 x 10(-5) mg ml(-1)), indicates a high potential for type II esterase in isoamyl acetate synthesis for production purposes. (C) 2008 Elsevier Ltd. All rights reserved.