Biocompatible ionic liquids act as a substrate reservoir and an in situ extracting agent in biotransformations with whole cells (see scheme). In the reduction of 4‐chloroacetophenone to (R)‐1‐(4‐chlorophenyl)ethanol, high product concentration (82 g L−1) and purity (99.6 % ee) were achieved without the addition of cofactors and without damaging the biocatalyst.

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An efficient fedbatch process for the production of Lactobacillus kefir DSM 20587 cells was developed. An improvement in space time yield of 270% (3.7 g(DCW) l(-1)-day(-1)) and in final enzyme activity of 440% (9.1 U/ml) was achieved on a 150 l scale by controlling the oxygen transfer rate to 7--9 mmol l(-1) h(-1). The cells exhibited good and highly stereoselective reducing activities against tert-butyl 6-chloro-3,5-dioxohexanoate. tert-Butyl (3R,5S)-6-chloro-dihydroxyhexanoate, a chiral building block for HMG-CoA reductase inhibitor synthesis, was produced with 47.5% yield and >99% ee at C(3)3 and C(5)5 in a simple batch biotransformation process.

An efficient whole cell biotransformation process using Lactobacillus kefir was developed for the asymmetric synthesis of tert-butyl (3R, 5S) 6-chloro-dihydroxyhexanoate, a chiral building block for the HMG-CoA reductase inhibitor. The effects of buffer concentration, temperature, pH and oxygen on the asymmetric reduction were investigated in batch reactions. Improvements in final product concentration and yields of 153% (120 mM) and 79% (0.85 mol/mol) with respect to the batch-process were achieved in an optimised fed-batch process. The pure substrate tert-butyl-6-chloro-3,5-dioxohexanoate was dispersed as microdroplets into the reaction system. This resulted in a space-time yield of 4.7 mmol l(-1) h(-1). A diastereomeric excess of >99% was measured for (3R, 5S) and (3S, 5S) tert-butyl 6-chloro-dihydroxyhexanoate.

Als biokompatibles Substratreservoir und In‐situ‐Extraktionsmittel fungiert die ionische Flüssigkeit bei Ganzzell‐Biotransformationen im Zweiphasensystem Puffer/ionische Flüssigkeit. Am Beispiel der Reduktion von 4‐Chloracetophenon zu (R)‐1‐(4‐Chlorphenyl)ethanol (siehe Schema) wird belegt, dass mit einer solchen Prozessführung ohne Zusatz teurer Cofaktoren hohe Produktkonzentrationen (82 g L−1) und ‐reinheiten (99.6 % ee) erzielt werden können.

klusiver der erforderlichen Instrumentierung und einer strukturangepassten Steuerung zur optimalen Produktbildung (s. Abb.). Abbildung.Ansicht des Enzym-Membran-Reaktors.

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