Three human cytochrome P450s, 3A4, 2C9 and 1A2, were each co-expressed with NADPH-P450 reductase in Escherichia coli and used in the preparative synthesis of drug metabolites. Low dissolved oxygen (DO) concentration (<1%) during expression was found to be critical for producing active P450s. Control of temperature, pH and glycerol supplementation in 10-L fermentations enhanced enzyme expression 31-86%. Additional improvements were obtained by altering media formulations, resulting in bicistronic expression levels of 890, 1,800 and 1,010 nmol/L for 3A4, 2C9 and 1A2, respectively. The P450 titers achieved in fermentors exceeded those in flask fermentations by 3- to 6-fold in this study and up to 10-fold when compared with previously reported literature. Intact cells and isolated membranes obtained from 10-L fermentations were used to establish an efficient bioconversion system for the generation of metabolites. To demonstrate the utility of this approach, known metabolites of the anabolic steroid testosterone, the anti-inflammatory agent diclofenac and the analgesic agent phenacetin, were generated using 3A4, 2C9 and 1A2, respectively. The reaction conditions were optimized for pH, temperature, DO concentration, use of co-solvent and glucose supplementation. Conversion yields of 29-93% were obtained from 1-L reactions, enabling isolation of 59 mg 6beta-hydroxytestosterone, 110 mg 4'-hydroxydiclofenac and 88 mg acetaminophen.

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An enzymatic process for desymmetrization of the prochiral diethyl 3‐[3',4'‐dichlorophenyl]glutarate, 1, an intermediate in the synthesis of a series of neurokinin (NK) receptor antagonists, has been developed and scaled up. The transformation catalyzed by Candida antarctica lipase B in either the free or the immobilized form was carried out at 100 g/L of substrate and proceeded with an average conversion of 97%. In the pilot plant, the process produced 200 kg of 2 in 3 batches with ee >99% and an average isolated yield of 80%. The immobilized enzyme preparation was particularly effective, achieving over 70,000 enzyme turnovers per batch.

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