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.