Biotransformation using halotolerant yeast in seawater: a sustainable strategy to produce R-(−)-phenylacetylcarbinol

Abstract

Acyloin condensation between benzaldehyde and decarboxylated pyruvate results in the production of R-(-)-phenylacetylcarbinol, a chiral precursor of the drug ephedrine. Huge research efforts have been made to improve the conditions of this reaction and to avoid the generation of by-products. Recently, we reported the advantages of using whole cells of the yeast Debaryomyces etchellsii as biocatalysts for this purpose. In this work, a new strategy, which fulfills green chemistry principles, is proposed and is based on using seawater as a gentle solvent. We demonstrate that, under these conditions, several improvements can be made compared to employing freshwater: (1) the conversion of the starting material in (R)-PAC is higher and with a minimum production of by-products; (2) it is possible to increase at least twofold the benzaldehyde load in the reaction medium; (3) cells can maintain their activity after several recycling rounds, which makes (R)-PAC production an easy and economical process.

Improved Biocatalytic Activity of the Debaryomyces Species in Seawater

“…As with organic solvents, it may differ in both freshwater and seawater. In fact our previous work found than benzaldehyde was more toxic for the S. etchellsii cells grown in a freshwater medium than in a seawater one . Hence the toxicity of the substrate of this reaction was analyzed in the four strains considered herein determining the lethal dose LD 50 .…”

“…A previous work employed whole cells of S. etchellsii to produce ( R )‐PAC and we found that using seawater to prepare the medium reaction could help to reduce the costs of the process because it allowed yeast cells to be reutilized several times . To determine if this was not particular case, this sort of experiments were also carried out herein.…”

“…A few recent reports have demonstrated the possibility of using seawater as an alternative to freshwater in biocatalytic processes –. The present work aimed to explore its scope and potential use in industry in‐depth.…”

“…Under these conditions, the conversion rate of the starting material in ( R )‐PAC was higher, with minimum by‐products production compared to freshwater. It was also possible to increase the benzaldehyde load in the reaction medium by at least twofold, and cells maintained their activity after several recycling rounds …”

“…polymorphus . These four strains have been shown to be able to grow in the presence of NaCl concentrations up to at least 7.5 % (w/v) …”