Fig. 8
Simple metabolic route for producing valuable compounds from lignin-derived aromatics. Lignin monomers are converted to acetyl-CoA as a final intermediate of protocatechuate metabolism in β-ketoadipate pathway. Lipid and polyhydroxyalkanoates are generated from the significant intermediate of acetyl-CoA via natural catabolic pathways in Rhodococci opacus (pink) and Pseudomonas putida KT2440 (orange), respectively [58, 126]. Rhodococcus sp. RHA1 is engineered to accumulate a significant amount of vanillin from feruilic acid by deleting vanillin dehydrogenase (Vdh) gene (green). Cis, cis-muconate has been proved to improve its yield in the engineered strain of P. putida by deletion of muconate cycloisomerase (CatB) gene and insertion of protocatechuate decarboxylase (AroY) gene (blue) [59]