Lignocellulose is an abundant agro-waste that can be biologically funnelled to produce many platform chemicals. Lignin, an aromatic polymer, is a major component of lignocellulosic biomass. Over 50 million tons of lignin is produced annually as a paper and pulp industry by-product. Due to lignin recalcitrance, most of it is burnt as boiler fuel. Only a few bacteria, like Acinetobacter baylyi ADP1, can naturally catabolize lignin. It is a gram-negative, non-pathogenic soil bacteria well known for utilizing aromatic compounds through the β-ketoadipate pathway. Its compact genome size (3.6 Mb), natural competence, high rate of homologous recombination, and the availability of a genetic toolset for genome engineering have made it a suitable choice for biological chassis. So far, A. baylyi ADP1 has been used to synthesize cyanophycin, wax esters, triacylglycerols, alkane, 1-alkene, poly-α-olefins, and mevalonate. Although A. baylyi ADP1 has an aromatic catabolism pathway, its utilization of aromatic lignin-derived monomers (LDMs) as a substrate is inefficient due to carbon catabolite repression and regulation at multiple levels.

Previous studies in our lab using adaptive laboratory evolution (ALE) on A. baylyi ADP1 have led to improved utilization of LDMs. Further, genome sequencing of these ALE-evolved strains revealed critical mutations in the regulatory genes (vanR and pcaU) of the β-ketoadipate pathway. Based on the in-silico analysis, we propose developing an A. baylyi ADP1 biological chassis through rational metabolic engineering that can efficiently utilize aromatic LDMs to produce value-added platform chemicals.