# Natural Low-Eutectic Solvent Co-Culture-Assisted Whole-Cell Catalyzed Synthesis of Ethyl (R)-4-Chloro-3-Hydroxybutyrate

## TL;DR

This study uses a natural low-eutectic solvent to enhance the production of a specific chemical compound through whole-cell catalysis.

## Contribution

The novel use of a co-culture with a natural low-eutectic solvent significantly improves the catalytic yield of (R)-4-chloro-3-hydroxybutyrate.

## Key findings

- Using 0.5% ChCl:U (1:2) in co-culture increased (R)-CHBE yield to 89.1%, a 58.2% improvement over the control.
- Co-culture with NADES outperformed secondary addition of NADES during the reaction buffer.
- ChCl:U (1:2) showed better catalytic performance than its individual components or single-component blends.

## Abstract

In this study, CGMCC NO:28566, a strain that can efficiently convert Ethyl 4-chloroacetoacetate(COBE) to (R)-4-chloro-3-hydroxybutyrate((R)-CHBE), was screened by soil-sieving bacteria. In order to improve the transformation effect of the strain, the natural low-eutectic solvent (NADES), which can alter the cell permeability, was utilized for assisted catalysis, and a better catalytic effect was achieved. This study was carried out using a co-culture of strains with NADES and secondary addition of NADES on the basis of co-culture, and 10 NADESs were screened at the same time. The co-catalytic effect of 0.5% (w/v) choline chloride: urea (1:2) (ChCl:U (1:2)) was found to be the most significant, with a yield of (R)-CHBE reaching 89.1%, which was 58.2% higher than that of the control group, with a 99% ee value. Furthermore, the catalytic results demonstrated that the co-culture of the strain with NADES during fermentation yielded superior outcomes to the secondary addition of NADES during the reaction buffer. Furthermore, the catalytic effect of ChCl:U (1:2) was demonstrated to be superior to that of its individual components or single-component blends, due to its distinctive valence bonding advantage. The results indicate that the addition of 0.5% (w/v) ChCl:U (1:2) during the co-culture process has the effect of improving cell permeability to a certain extent, thereby increasing the contact between the substrate and the enzyme during the whole-cell catalytic reactions.