Response surface methodology (RSM) was used to optimize the oxidizing the omeprazole sulfide to (S)-omeprazole catalyzed by environmentally friendly catalyst soybean pod peroxidase (SPP) in cetyltrimethylammonium bromide (CTAB)/isooctane/n-butyl alcohol/water water-in-oil microemulsions. With the initial concentration of SPP of 3200 U ml-1, the conversion of the omeprazole sulfide, the (S)-omeprazole yield and ee were 93.75%, 91.56% and 96.08%, respectively, under the optimal conditions: Wo of 15.85, the concentration of H2O2 of 22.44 mM and reaction temperature of 49.68 °C, respectively. The proposed mechanism of asymmetric sulfoxidations catalyzed by SPP involves three concomitant mechanisms as follows: (1) a two-electron reduction of SPP-I, (2) a single-electron transfer to SPP-I and (3) nonenzymatic reactions, including five enzymatic and two nonenzymatic reactions, which is reasonable and can express the oxidations. With 5.44% of the average relative error, a kinetic model based on the mechanisms fitting observed data very well was established, and the SPP-catalyzed reactions including both the two-electron reduction and the single-electron transfer mechanisms obey ping-pong mechanism with substrate and product inhibition, while nonenzymatic reactions follow a power law. This study has also demonstrated the feasibility of SPP as a substitute with low cost, excellent enantioselectivity and better thermal stability.

The asymmetric sulfoxidation catalyzed by soybean pod peroxidase (SPP) in water-in-oil microemulsions were carried out with the yield of 91.56% and e.e of 96.08% at the activity of SPP of 3200 U ml-1 and 50℃ for 5 h. The mechanism with a two-electron reduction of SPP-I is accompanied with a single-electron transfer to SPP-I and nonenzymatic reactions, indicating that three concomitant sub-mechanisms contribute to the asymmetric oxidation involving five enzymatic and two nonenzymatic reactions, which can represent the asymmetric sulfoxidation of organic sulfides to form enantiopure sulfoxides. With 5.44% of the average relative deviation, a kinetic model fitting experimental data very well was developed. The enzymatic reactions may follow ping-pong mechanism with substrate inhibition of H2O2 and product inhibition of esomeprazole, while nonenzymatic reactions, a power law. Those results indicate that SPP with a lower cost and higher thermal stability may be used as an effective substitute for Horseradish Peroxidase.

The asymmetric sulfoxidation catalyzed by soybean pod peroxidase (SPP) in water-in-oil microemulsions were carried out with the yield of 91.56% and e.e of 96.08% at the activity of SPP of 3200 U ml-1 and 50℃ for 5 h. The mechanism with a two-electron reduction of SPP-I is accompanied with a single-electron transfer to SPP-I and nonenzymatic reactions, indicating that three concomitant sub-mechanisms contribute to the asymmetric oxidation involving five enzymatic and two nonenzymatic reactions, which can represent the asymmetric sulfoxidation of organic sulfides to form enantiopure sulfoxides. With 5.44% of the average relative deviation, a kinetic model fitting experimental data very well was developed. The enzymatic reactions may follow ping-pong mechanism with substrate inhibition of H2O2 and product inhibition of esomeprazole, while nonenzymatic reactions, a power law. Those results indicate that SPP with a lower cost and higher thermal stability may be used as an effective substitute for Horseradish Peroxidase.

The asymmetric sulfoxidation of the omeprazole thioether to synthesize esomeprazole catalyzed by immobilized cells of a mutant of Rhodococcus rhodochrous ATCC 4276 in the chloroform–water biphasic system was carried out at a high substrate concentration (200mM) and optimized using response surface methodology (RSM). The optimal yield of esomeprazole obtained was 94.8% with e.e. (>99%) without the formation of the sulfone. A quadratic polynomial model was developed with R2 of 0.9998, which indicates that the model predicts the observed data with very high accuracy. The mutant exhibited a high enantioselective, activity and substrate and product tolerance. The significant improvement of substrate tolerance may mainly be contributed by employing the chloroform–water biphasic system because almost all substrates may partitioned in the organic phase, resulting in little damage and inhibition to cells by substrates.

Response surface methodology(RSM)was used to optimize the oxidizing the omeprazole sulfide to(S)-omeprazole catalyzed by soybean pod peroxidase(SPP) in cetyltrimethylammonium bromide (CTAB)/isooctane/n-butyl alcohol/water water-in-oil microemulsions. With the initial concentration of SPP of 3200 U ml-1, the conversion of the omeprazole sulfide, the (S)-omeprazole yield and ee were 93.75%, 91.56% and 96.08%, respectively. The mechanism of asymmetric sulfoxidations catalyzed by SPP involves three concomitant mechanisms as follows:(1) a two-electron reduction of SPP-I, (2) a single-electron transfer to SPP-I and (3) nonenzymatic reactions. With 5.44% of the average relative error, a kinetic model based on the mechanisms was established, and the SPP-catalyzed reactions including both the two-electron reduction and the single-electron transfer mechanisms obey ping-pong mechanism with substrate and product inhibition, while nonenzymatic reactions follow a power law. This study has also demonstrated the feasibility of SPP as a substitute with low cost, excellent enantioselectivity and better thermal stability.

The asymmetric sulfoxidation catalyzed by soybean pod peroxidase (SPP) in water-in-oil microemulsions were carried out with the yield of 91.56% and e.e of 96.08% at the activity of SPP of 3200 U ml-1 and 50℃ for 5 h. The mechanism with a two-electron reduction of SPP-I is accompanied with a single-electron transfer to SPP-I and nonenzymatic reactions, indicating that three concomitant sub-mechanisms contribute to the asymmetric oxidation involving five enzymatic and two nonenzymatic reactions, which can represent the asymmetric sulfoxidation of organic sulfides to form enantiopure sulfoxides. With 5.44% of the average relative deviation, a kinetic model fitting experimental data was developed. The enzymatic reactions may follow ping-pong mechanism with substrate inhibition of H2O2 and product inhibition of esomeprazole, while nonenzymatic reactions, a power law. Those results indicate that SPP with a lower cost and higher thermal stability may be used as an effective substitute for Horseradish Peroxidase.

(S)-Omeprazole is a very effective anti-ulcer medicine, and it is a significant challenge to prepare it by whole cells and to substantially increase the substrate concentration. In the chloroform–water biphasic system, resting cells of the mutant of Rhodococcus rhodochrous(R. rhodochrous)ATCC 4276 were employed to catalyze the bio-oxidation of the omeprazole sulfide for preparation of (S)-omeprazole. At a high substrate concentration(180 mM) and cell concentration(100 g/L), the bio-oxidation was optimized using response surface methodology(RSM), and the optimal yield of (S)-omeprazole obtained was 92.9% with enantiomeric excess(e.e.) (>99%), and no sulfone product was detected under the optimal conditions: the reaction temperature was 37°C, pH of phosphate buffer, 7.3 and the reaction time, 43h respectively. A quadratic polynomial model was established, which predicts the experimental data with very high accuracy according to R2 of 0.9990. The chloroform–water biphasic system may mainly contribute the significant improvement of substrate tolerance because almost all substrates may partitioned in the organic phase (water solubility of omeprazole sulfide is only about 0.5 mg/ml), resulting in little damage and inhibition to cells by substrates. The mutant of R. rhodochrous ATCC 4276 exhibited a high enantioselective, activity and substrate and product tolerance. The aerated flask provides enough oxygen for a high concentration of cells. Accordingly, the bio-oxidation is thus more promising for efficient preparation of chiral sulfoxides.

Response surface methodology (RSM) was used to optimize the oxidation of the omeprazole sulfide to (S)-omeprazole catalyzed by environmentally friendly catalyst soybean pod peroxidase (SPP) in cetyltrimethylammonium bromide (CTAB)/isooctane/n-butyl alcohol/water water-in-oil microemulsions. With the initial concentration of SPP of 3200 U ml-1, the conversion of the omeprazole sulfide, the (S)-omeprazole yield and ee were 93.75%, 91.56% and 96.08%, respectively, under the optimal conditions: Wo of 15.85, the concentration of H2O2 of 22.44 mM and reaction temperature of 49.68 ℃, respectively. The proposed mechanism of asymmetric sulfoxidations catalyzed by SPP involves three concomitant mechanisms as follows: (1) a two-electron reduction of SPP-I, (2) a single-electron transfer to SPP-I and (3) nonenzymatic reactions, including five enzymatic and two nonenzymatic reactions, which is reasonable and can express the oxidations. With 5.44% of the average relative error, a kinetic model based on the mechanisms fitting observed data very well was established, and the SPP-catalyzed reactions including both the two-electron reduction and the single-electron transfer mechanisms obey ping-pong mechanism with substrate and product inhibition, while nonenzymatic reactions follow a power law. This study has also demonstrated the feasibility of SPP as a substitute with low cost, excellent enantioselectivity and better thermal stability.