Engineered Microbial Production of 2-Pyrone-4,6-Dicarboxylic Acid from Lignin Residues for Use as an Industrial Platform Chemical

As one of the most abundant materials in nature, lignin has been used widely in co-generation operations and for fine chemicals and bio-fuels production. These uses, although important, are of relatively low value. Lignin contains many aromatic compounds with useful structures, and it is potentially more profitable to produce high-value fine chemicals from the low-molecular weight lignin fraction while using the high-molecular weight fraction for fuel or other applications. A transgenic P. putida bacterial strain PDHV85 was developed with the capability to convert vanillin, vanillic acid, and syringaldehyde to 2-pyrone-4,6-dicarboxylic acid (PDC), a novel platform chemical that can produce a variety of bio-based polymers. Initial testing with vanillin showed promise for lignin conversion. Testing for this, we used kraft lignin, Japanese cedar (Cryptomeria japonica), or birch (Betula platyphylla) to represent some of the most abundant industrial lignin sources from softwood and hardwood. Repeated manipulation of culture conditions and strain adaptation allowed conversion of these extracts to PDC by PDHV85, which has not previously been reported in a bacterial strain. No inhibition was observed at 0.14 mg/mL kraft lignin extract, 1.14 mg/mL Japanese cedar extract, nor 1.15 mg/mL birch extract when using the optimized growth conditions.