Simultaneous Improvements of Pseudomonas Cell Growth and Polyhydroxyalkanoate Production from a Lignin Derivative for Lignin-Consolidated Bioprocessing

With the recent advances in processing carbohydrates in lignocellulosics for bioproducts, almost all biological conversion platforms result in the formation of a significant amount of lignin by-products, representing the second most abundant feedstock on earth. However, this resource is greatly underutilized due to its heterogeneity and recalcitrant chemical structure. Thus, exploiting lignin valorization routes would achieve the complete utilization of lignocellulosic biomass and improve cost-effectiveness. The culture conditions that encourage cell growth and polyhydroxyalkanoate (PHA) accumulation are different. Such an inconsistency represents a major hurdle in lignin-to-PHA bioconversion. In this study, we traced and compared transcription levels of key genes involved in PHA biosynthesis pathways in Pseudomonas putida A514 under different nitrogen concentrations to unveil the unusual features of PHA synthesis. Furthermore, an inducible strong promoter was identified. Thus, the molecular features and new genetic tools reveal a strategy to coenhance PHA production and cell growth from a lignin derivative.