# Whole-Cell Biocatalysis for the Production of Structurally Diverse Methoxydihydrochalcones: Broad Activity of the Yarrowia Clade

## TL;DR

This paper explores the use of Yarrowia yeast strains to efficiently produce dihydrochalcones from methoxychalcones, highlighting their broad substrate tolerance and potential for sustainable synthesis.

## Contribution

The study demonstrates the broad chemoselective reduction capability of Yarrowia clade strains, particularly Y. lipolytica KCh 71, for synthesizing diverse dihydrochalcones.

## Key findings

- Yarrowia strains consistently showed high hydrogenation activity for reducing methoxychalcones to dihydrochalcones.
- Y. lipolytica KCh 71 efficiently converted various methoxychalcone derivatives with yields between 62% and 92%.
- Bioinformatic analysis suggests Old Yellow Enzymes (OYE) are responsible for the observed reductions in the Yarrowia clade.

## Abstract

Whole-cell biocatalysis presents a sustainable and efficient approach for the selective reduction in α,β-unsaturated bonds in flavonoid derivatives. This study investigates the capability of yeast strains from the Yarrowia clade to catalyze the chemoselective reduction of 4′-methoxychalcone (1a) to its dihydro derivative. All tested strains exhibited similarly high hydrogenation activity, indicating a broadly conserved enoate reductase function within the clade. Among them, Yarrowia lipolytica KCh 71, previously reported and well characterized in the literature, was selected for preparative-scale transformation of a diverse series of synthetic methoxychalcones bearing additional methoxy groups in positions C-2, C-3, C-4, C-5, and C-6 of ring B. All derivatives were effectively converted into the corresponding dihydrochalcones, with yields ranging from 62% to 92%. Among the tested derivatives, the 2′,4′,6′-trimethoxy chalcone (7a) did not undergo biotransformation under our conditions, whereas mono- and di-methoxy derivatives (2a–6a) were efficiently reduced. These results confirm the broad substrate tolerance, high efficiency, and potential scalability of Y. lipolytica KCh 71, supporting its potential as a whole-cell biocatalyst for the sustainable synthesis of bioactive dihydrochalcones. The consistently high hydrogenation activity observed across 21 tested strains suggests the involvement of evolutionarily conserved enoate reductases. Bioinformatic analysis supports that the Yarrowia clade possesses a robust complement of Old Yellow Enzymes (OYE), providing a reliable enzymatic basis for the observed chemoselective reductions. All Yarrowia tested strains showed the same general transformation type, although the extent and rate of conversion differed among strains, and Y. lipolytica KCh 71 was one of the most tolerant. The broad reduction in α,β-unsaturated chalcones is consistent with the action of flavoenzymatic ene-reductases, particularly Old Yellow Enzyme (OYE)–like reductases. Bioinformatic analysis of Yarrowia genomes reveals putative OYE homologs, supporting this mechanistic interpretation, although the specific enzymes were not identified in this study.