Characterization of Alcohol Dehydrogenase from Permeabilized Brewer's Yeast Cells Immobilized on the Derived Attapulgite Nanofibers

Alcohol dehydrogenase (ADH) from permeabilized brewer's yeast was immobilized on derived attapulgite nanofibers via glutaraldehyde covalent binding. The effect of immobilization on ADH activity, optimum temperature and pH, thermal, pH and operational stability, reusability of immobilized ADH, and bioreduction of ethyl 3-oxobutyrate (EOB) to ethyl(S)-3-hydroxybutyrate ((S)-EHB) by the immobilized ADH were investigated. The results show the immobilized ADH retained higher activity over wider ranges of pH and temperature than those of the free. The optimum temperature and pH were 7.5 and 35 °C, respectively, and 58% of the original activity was retented after incubation at 35 °C for 32 h. More importantly, in bioreduction of EOB mediated by immobilized ADH, the conversion of substrate and enantiomeric excess (ee) of product reached 88% and 99.2%, respectively, within 2 h and retained about 42% of the initial activity after eight cycles.