Efficient reduction of aromatic ketones with NADPH regeneration by using crude enzyme from Rhodotorula cells and mannitol as cosubstrate

An enzyme-coupled system, containing a ketoreductase for prochiral ketones reduction and a mannitol dehydrogenase for NADPH regeneration, was discovered from the cell-free extract of Rhodotorula sp. AS2.2241 and used successfully for the asymmetric reduction of 2-acetylpyridine, giving (S)-1-(2-pyridine)ethanol in >99% ee with recycling of NADPH for 4220 times. Moreover, the endogenously coupled enzymes system could also reduce various aromatic ketones such as 3- and 4-acetylpyridines with 96–99% ee.