Engineered Pseudomonas putida Simultaneously Catabolizes Five Major Components of Corn Stover Lignocellulose: Glucose, Xylose, Arabinose, p-coumaric Acid, and Acetic Acid

by Joshua R.Elmore, Gara N.Dexter, DaviniaSalvachúa, MarykateO'Brien, Dawn M.Klingeman,KentGorday, Joshua K.Michener, Darren J.Peterson, Gregg T.Beckham, Adam M.Guss (Metabolic Engineering) Engineered P. putida to catabolize xylose and arabinose. Identified bottlenecks in xylose catabolism in P. putida and improved growth rate. Max sugar consumption rate in corn stover hydrolysate was 3.3 g/L/h. Simultaneous catabolism of glucose, xylose, arabinose, aromatics, and organic acids.

Valorization of all major lignocellulose components, including lignin, cellulose, and hemicellulose is critical for an economically viable bioeconomy. In most biochemical conversion approaches, the standard process separately upgrades sugar hydrolysates and lignin.

Here, we present a new process concept based on an engineered microbe that could enable simultaneous upgrading of all lignocellulose streams, which has the ultimate potential to reduce capital cost and enable new metabolic engineering strategies. Pseudomonas putida is a robust microorganism capable of natively catabolizing aromatics, organic acids, and D-glucose. We engineered this strain to utilize D-xylose by tuning expression of a heterologous D-xylose transporter, catabolic genes xylAB, and pentose phosphate pathway (PPP) genes tal-tkt. We further engineered L-arabinose utilization via the PPP or an oxidative pathway.

This resulted in a growth rate on xylose and arabinose of 0.32 h⁻¹ and 0.38 h⁻¹, respectively. Using the oxidative L-arabinose pathway with the PPP xylose pathway enabled D-glucose, D-xylose, and L-arabinose co-utilization in minimal medium using model compounds as well as real corn stover hydrolysate, with a maximum hydrolysate sugar consumption rate of 3.3 g/L/h. After modifying catabolite repression, our engineered P. putida simultaneously co-utilized five representative compounds from cellulose (D-glucose), hemicellulose (D-xylose, L-arabinose, and acetic acid), and lignin-related compounds (p-coumarate), demonstrating the feasibility of simultaneously upgrading total lignocellulosic biomass to value-added chemicals. READ MORE