Engineering Acinetobacter baylyi ADP1 for mevalonate production from lignin-derived aromatic compounds

Utilization of lignin, an abundant renewable resource, is limited by its heterogenous composition and complex structure. Biological valorization of lignin provides advantages over traditional chemical processing as it occurs at ambient temperature and pressure and does not use harsh chemicals. Furthermore, the ability to biologically funnel heterogenous substrates to products eliminates the need for costly downstream processing and separation of feedstocks. However, lack of relevant metabolic networks and low tolerance to degradation products of lignin limits the application of traditional engineered model organisms. To circumvent this obstacle, we employed Acinetobacter baylyi ADP1, which natively catabolizes lignin-derived aromatic substrates through the β-ketoadipate pathway, to produce mevalonate from lignin-derived compounds. We enabled expression of the mevalonate pathway in ADP1 and validated activity in the presence of multiple lignin-derived aromatic substrates. Furthermore, by knocking out wax ester synthesis and utilizing fed-batch cultivation, we improved mevalonate titers 7.5-fold to 1014 mg/L (6.8 mM). This work establishes a foundation and provides groundwork for future efforts to engineer improved production of mevalonate and derivatives from lignin-derived aromatics using ADP1.