# Reaction Engineering for Asymmetric R‐/S‐PAC Synthesis With Ephedrine or Pseudoephedrine Dehydrogenase in Pickering Emulsion

## TL;DR

This paper describes using enzymes in a special emulsion setup to efficiently produce specific forms of a chemical important for drug manufacturing.

## Contribution

The study introduces a novel application of design of experiments in Pickering emulsions for asymmetric PAC synthesis using EDH and PseDH enzymes.

## Key findings

- A space-time yield of 4.2 g L⁻¹ h⁻¹ and 83.2% conversion were achieved with EDH in the BioPE system.
- Using PseDH in the BioPE system resulted in a space-time yield of 4.4 g L⁻¹ h⁻¹ and 64.5% conversion.

## Abstract

The synthesis of enantiopure α‐hydroxy ketones, particularly R‐ and S‐phenylacetylcarbinol (PAC), represents an important process in the pharmaceutical industry, serving as a pivotal step in the production of drugs. Recently, two novel enzymes, ephedrine dehydrogenase (EDH) and pseudoephedrine dehydrogenase (PseDH), have been described. These enzymes enable the specific reduction of 1‐phenyl‐1,2‐propanedione (PPD) to R‐PAC and S‐PAC, respectively. In this study, we transferred these enzymes into Pickering emulsions, which is an attractive reaction set‐up for large‐scale synthesis. The bioactive w/o Pickering emulsion (bioactive Pickering emulsion [BioPE]), in which methyl tert‐butyl ether served as the continuous phase, was stabilized by silica nanoparticles. Formate dehydrogenase from Rhodococcus jostii was utilized for cofactor regeneration. Given the considerable complexity of the BioPE, this reaction system underwent a first‐time application of design of experiment (DOE) for systematic engineering. A definitive screening design was employed to identify significant factors affecting space‐time yield (STY) and conversion. Response surface methodology was used to optimize the conditions, resulting in the observation of a high STY of 4.2 g L⁻¹ h⁻¹ and a conversion of 83.2% for BioPE with EDH, and an STY of 4.4 g L⁻¹ h⁻¹ and a conversion of 64.5% for BioPE with PseDH.