Superabsorbed alcohol dehydrogenase--a new catalyst for asymmetric reductions.

A new immobilisate of alcohol dehydrogenase (ADH) is described in which all components for the reaction, i.e. enzyme, the coenzyme NADP(+), the buffer and other cofactors (trace elements), are immobilized together. It is an all-inclusive catalyst. The support is a cheap, commercially-available, superabsorbent polymer. The immobilisation is easy to achieve. The superabsorbed ADH is, even when dried, a stable and storable catalyst for at least five weeks at -18 degrees C. Asymmetric reductions of the prochiral ketones, acetophenone, 4-acetylpyridine and ethyl acetoacetate, with a superabsorbed ADH from Lactobacillus brevis (ADH 002) and a superabsorbed ADH from Thermoanaerobicum sp. (ADH 005) in 2-propanol as both the organic solvent and the cofactor-regenerating substrate are given. Yields of chiral (R) and (S)-alcohols from 97-100% were achieved within 18 to 48 h with enantiomeric excesses of >99%. The superabsorbed ADH was easily separated by filtration and could be reused at least four times.