Note on Biotransformations with Halobacterium halobium: Reduction of Ethyl 3-Oxobutanoate and Hydrolysis of Ethyl 3-Hydroxybutanoate. Cooperative Effects of Reductase and Hydrolase

Article abstract of DOI:10.1002/hlca.19890720420

The archaebacterium Halobacterium halobium, growing in saturated NaCl solution, is tested for its ability to achieve biotransformations.We found that this microorganism does accept only a small veriety of compounds as substrates.Ethyl acetoacetate (1) is reduced to ethyl (S)-3-hydroxybutanoate (2) of optical purity of 40-76 percent, but in low chemical yields.The reduction is accompanied by hydrolysis of the hydroxy-ester to 3-hydroxybutanoic acid (3).Hydrolysis of rac-ester 2 by Halobacterium halobium gives (R)-2 of optical purity of up to 88 percent, depending upon reaction time, together with the almost racemic hydroxy-acid 3, both in low chemical yields.Hopes that the 'extremist' Halobacterium halobium would be able to effect unique conversions were not fulfilled.