Oxidative Depolymerization of Lignosulfonates for Muconic Acid Production Using Recombinant Pseudomonas putida CJ475

Lignosulfonate, a macromolecular byproduct derived from the paper and pulp industry, is a promising feedstock for bioconversion processes due to its rich carbon content and widespread availability. We here present an approach for the production of muconic acid through the optimization of the oxidative depolymerization of lignosulfonate and its further conversion using a recombinant Pseudomonas putida strain. This process yielded a stream containing a diverse mixture of low-molecular-weight aromatic compounds, the highest yield being that of vanillin, of 5.77 wt%. When bioconversion was performed with the P. putida strain CJ475, previously engineered for the conversion of vanillin to muconic acid, no conversion was initially observed due to the inhibitory effect of the depolymerized lignosulfonate fraction on bacterial growth. However, a simple additional extraction step with ethyl acetate led to the successful conversion of the substrate with a yield of 1.3 ± 0.06 mol muconic acid/mol vanillin in the stream. This study demonstrates the feasibility of utilizing oxidatively depolymerized lignosulfonates as a sustainable carbon source for biobased muconic acid production. It also marks a significant step forward in the utilization of lignocellulosic biomass for sustainable high-value biochemical production, as well as providing valuable insights into the development of bioprocesses utilizing complex, lignin-rich feedstocks.