Biocatalysis in organic solvent systems using thermostable enzymes: esterase-catalysed transesterification of Z-L-tyrosine p-nitrophenyl ester

The esterase-catalysed transesterification of N-carbobenzoxy-l-tyrosinep-nitrophenol ester (Z-Tyrp-NPE) with methanol was studied with water: methanol cosolvent and with dry ethyl acetate as solvent. The crude esterase employed was fully thermostable in both solvents at 44°C. At 88°C esterase activity decreased by 90% in water: methanol (10% v/v) and 30% in dry ethyl acetate after 4 h. The initial rate of transesterification was the same order of magnitude, i.e. 1.7 and 0.95 μmol h−1 unit−1 esterase in the two solvents, respectively. However, Z-TyrpNPE solubility was about 50-fold greater in ethyl acetate compared to the water: methanol cosolvent system, accounting for a 50-fold greater quantity of product formed per experiment in ethyl acetate.Keywords: Esterase; thermophilic enzyme; organic solvent catalyses; transesterification