# Sustainable Nonenantioselective Production and Stereochemical Characterization of the Lignin‐Derived Chiral Building Block 3‐Carboxymuconolactone

## TL;DR

A new method is developed to produce a chiral compound from lignin at low cost and under mild conditions, suitable for industrial use.

## Contribution

The first sustainable nonenantioselective production and stereochemical characterization of 3-carboxymuconolactone from lignin is achieved.

## Key findings

- A one-pot process produced racemic 3CML with 93.1% yield at 28°C without pressure or metal reagents.
- The stereochemistry of racemic 3CML was characterized using chiral HPLC and circular dichroism.
- Vanillic acid was efficiently converted into 3CML using engineered Pseudomonas putida and acidic treatment.

## Abstract

To promote the comprehensive utilization of renewable lignocellulosicbiomass, a practical technology for the nonenantioselective production of 3‐carboxymuconolactone (3CML), a lignin‐derived chiral building block, is presented. Although an engineered Pseudomonas putida strain with plasmids containing bacterial and fungal genes was previously used to convert lignin‐derived aromatic compounds into optically pure 4S‐3CML, using the enantiomeric pair 4S‐3CML and 4R‐3CML as polymer building blocks in appropriate blending ratios can be expected to afford novel materials such as polylactic acid with tunable physical properties for targeted applications. Therefore, in this study, P. putida was engineered to convert vanillic acid, the major aromatic compound derived from lignin, into 3‐carboxy‐cis,cis‐muconate, which was then chemically converted into racemic 3CML under acidic conditions. Using a chiral high performance liquid chromatography–circulardichroism system, racemic 3CML was stereochemically characterized on the basis of the enantiomers. A one‐pot process for the production of racemic 3CML was established by combining fed‐batch fermentation with subsequent acidic treatment using a jar fermenter, affording 6.6 g/L 4S‐3CML and 7.2 g/L 4R‐3CML in a high yield of 93.1%. The developed process can be consistently performed at 28°C without requiring pressure or metal reagents and allows using a reduced volume of solvent, offering clear advantages for industrial applications.

The first stereochemical characterization and sustainable nonenantioselective production of 3‐carboxymuconolactone (3CML), a lignin‐derived chiral building block, are presented. The developed process consistently proceeds at 28°C without requiring pressure or metal reagents and allows reducing the amount of solvent, offering clear advantages for industrial applications.© 2026 WILEY‐VCH GmbH