Bioconversion of an untapped lignin monomer into a new pyridine-dicarboxylic acid building-block

Abstract

Bioconversion processes to transform lignin derived compounds into sustainable materials with enhanced properties are capable to integrate lignin valorization and bio-based plastics management in a circular economy model. In this work, synthetic metabolic pathways were designed and implemented into Pseudomonas putida KT2440 to efficiently transform the untapped lignin derived monomer homovanillic acid (HVA) into 5-(carboxymethyl)-pyridine-2-carboxylic acid (2,5-CPDCA), a yet unexplored pyridine dicarboxylic acid that can act as a terephthalate analog for the synthesis of new polymers. O-demethylation was the main bottleneck in HVA bioconversion, and it was addressed by engineering an optimized P. putida biocatalyst expressing a heterologous 5-aminolevulinic acid synthase that boost the activity of a heme-dependent cytochrome P450 HVA demethylase. High bioconversion yields were achieved under resting cell conditions using real depolymerized lignin samples. The synthesis and characterization of a novel polymer derived from 2,5-CPDCA confirms its potential as a promising sustainable platform chemical.