Lignin conversion to β-ketoadipic acid by <i>Pseudomonas putida</i> via metabolic engineering and bioprocess development
Allison Z. Werner, William T. Cordell, Ciaran W. Lahive, Bruno Colling Klein, Christine A. Singer, Eric C. D. Tan, Morgan A. Ingraham, Kelsey J. Ramirez, Dong Hyun Kim, Jacob Nedergaard Pedersen, Christopher W. Johnson, Brian F. Pfleger, Gregg T. Beckham, Davinia Salvachúa
Abstract
Bioconversion of a heterogeneous mixture of lignin-related aromatic compounds (LRCs) to a single product via microbial biocatalysts is a promising approach to valorize lignin. Here, Pseudomonas putida KT2440 was engineered to convert mixed p-coumaroyl– and coniferyl-type LRCs to β-ketoadipic acid, a precursor for performance-advantaged polymers. Expression of enzymes mediating aromatic O -demethylation, hydroxylation, and ring-opening steps was tuned, and a global regulator was deleted. β-ketoadipate titers of 44.5 and 25 grams per liter and productivities of 1.15 and 0.66 grams per liter per hour were achieved from model LRCs and corn stover-derived LRCs, respectively, the latter representing an overall yield of 0.10 grams per gram corn stover-derived lignin. Technoeconomic analysis of the bioprocess and downstream processing predicted a β-ketoadipate minimum selling price of $2.01 per kilogram, which is cost competitive with fossil carbon-derived adipic acid ($1.10 to 1.80 per kilogram). Overall, this work achieved bioproduction metrics with economic relevance for conversion of lignin-derived streams into a performance-advantaged bioproduct.