Current Status of Pseudomonas putida Engineering for Lignin Valorization

Lignin, a complex aromatic polymer, is a structural component of plant biomass. It decomposes with difficulty because of its rigidity properties, however, lignin valorization is essential for the economics of lignocellulosic biorefineries. Pseudomonas putida has been extensively investigated as a promising host strain for lignin valorizations due to intrinsic traits, such as low nutritional requirement, high tolerance to toxicity, and metabolic versatility with a wide spectrum of substrates, such as aromatic compounds. Although a naturally occurring, lignin-utilizing P. putida strain has been reported, it is necessary to engineer the genome of P. putida for efficient lignin utilization. For biological lignin valorization, the decomposition of lignin polymer to low-molecular weight compounds and transformation of lignin-derived aromatic compounds to value-added chemicals is essential. Various tools of synthetic biology have been developed for the genome engineering of P. putida; efforts in metabolic engineering have been made to expand aromatic substrate specificity and to improve productivity of value-added chemicals. Development of high-performance bio-parts and biosensors for lignin valorization has also been done. In this review, we present recent research on genome engineering tools developed for P. putida and metabolic engineering employed in P. putida to improve lignin valorization.