Ultrasound-assisted (R)-phenylephrine whole-cell bioconversion by S. marcescens N10612

The strain Serratia marcescens N10612 is used to perform the bioconversion of 1-(3-hydroxyphenyl)-2-(methyamino)-ethanone (HPMAE) to (R)-phenylephrine ((R)-PE), which is an ephedrine drug substitute. The use of an ultrasound approach is found to improve the efficiency of the (R)-PE bioconversion. The optimization of the (R)-PE bioconversion is carried out by means of statistical experiment design. The optimal conditions obtained are 1.0 mM HPMAE, 18.68 g/L glucose and ultrasound power of 120 W, where the predicted specific rate of the (R)-PE bioconversion is 31.46 ± 2.22 (ìmol/h/g-cells) and the experimental specific rate is 33.27 ± 1.46 (ìmol/h/g-cells), which is 3-fold higher than for the operation under ultrasound power of 200 W (11.11 ìmol/h/g-cells) and 4.3-fold higher than for the shaking operation (7.69 ìmol/h/g-cells). The kinetics study of the bioconversion also shows that under the ultrasound operation, the optimal rate (Vmax) of the (R)-PE bioconversion increases from 7.69 to 11.11 (μmol/h/g-cells) and the substrate inhibition constant (KSi) increases from 1.063 mM for the shaking operation to 1.490 mM for ultrasound operation.