Valorizing Lignin and Coprecursors into Homogeneous Polyhydroxyalkanoates by Engineered Pseudomonas putida

Lignin, the largest renewable aromatic resource, holds great potential for valorization into valuable products. Biotransforming lignin into polyhydroxyalkanoate (PHA) can play a crucial role in addressing environmental concerns and fostering a sustainable bioeconomy. However, achieving homogeneity of PHA and high bioconversion efficiency of lignin are primary challenges. Engineering and precursor control strategies were thus designed to enhance the homogeneous PHA synthesis from lignin. The results showed that using precursors from lignin hydrolysate can boost PHA accumulation and regulate its monomer composition by Pseudomonas putida KT2440. Engineered P. putida KTYY06 was constructed by blocking PHA degradation, enhancing PHA synthesis and rewriting the fatty acid β-oxidation pathway. A remarkable homogeneous PHA containing 91.4% 3-hydroxyoctanoate monomer was achieved from co-feeding lignin-derived aromatics and precursors. Implementing a fed-batch fermentation strategy led to the highest PHA titer of 2.46 g/L, representing a 143.6% increase over the batch mode. P. putida KTYY06 also exhibited efficient PHA production, achieving an 85% 3-hydroxyoctanoate monomer content when using actual lignin streams. Overall, these multidimensional approaches of genetic modification, precursor regulation, and fermentation optimization show great promise for generating high-homogeneity PHA. The implications of this novel production strategy are significant, offering tailored PHAs with unique properties for advanced applications.