Reactivity and stability of mycelium-bound carboxylesterase from Aspergillus oryzae

The reactivity and thermostability of a novel mycelium-bound carboxylesterase from lyophilized cells of Aspergillus oryzae are explored in organic solvent. Ethanol acetylation was selected as reference esterification reaction. High carboxylesterase activity cells were used as biocatalyst in batch esterification tests at 12.5 < So < 125 mmol L-1, 5.0 < Xo < 30 g L-1, 0.49 < log P < 4.5 and 30 < T < 80°C, as well as in residual activity tests after incubation at 40 < T < 90°C. The starting rates of product formation were used to estimate with the Arrhenius model the apparent activation enthalpies of the enzymatic reaction (29-33 kJ mol-1), the reversible unfolding (56-63 kJ mol-1), and the irreversible denaturation (22 kJ mol-1) of the biocatalyst.