Expanding the substrate spectrum in engineered Pseudomonas taiwanensis for efficient production of 4-coumarate from lignocellulosic sugars

Abstract Aromatics are important building blocks for polymers, pharmaceuticals, and advanced materials, but their current production relies on petrochemical processes. Biotechnological de novo production from renewable bio-based feedstocks with microbial cell factories provides a sustainable alternative. In this study, we enhanced 4-coumarate production in Pseudomonas taiwanensis from glucose and glycerol compared to previously published producers. This was achieved through heterologous expression of tyrosine ammonia-lyase (TAL) from Rivularia sp. PCC7116, which debottlenecked the specific deamination of tyrosine. Moreover, deletion of the phosphoenolpyruvate carboxylase-encoding gene ppc further increased the production. Subsequently, the substrate spectrum for efficient aromatics production was expanded to include the abundant pentoses, xylose and arabinose. Heterologous non-oxidative assimilation pathways were integrated into P. taiwanensis GRC3 chassis strains and growth on xylose and arabinose was improved through adaptive laboratory evolution, whole-genome sequencing, and reverse engineering. Optimized catabolic modules were then transferred to producer strains to enhance or enable 4-coumarate production from xylose and arabinose. Notably, the product yield on xylose increased approximately 3.5-fold with the non-oxidative xylose isomerase pathway compared to the oxidative native Weimberg pathway, without compromising yields on glucose. For the final strain, P. taiwanensis GRC3Δ6-TYR2Δ ppc -REXA- attTn7 :: P 14f -RpcTAL , product yields were significantly higher on xylose (38.2% (Cmol/Cmol)) and arabinose (39.7% (Cmol/Cmol)) than on glucose (26.0% (Cmol/Cmol)). 4-Coumarate production was characterized on mixtures of glucose, xylose, and arabinose to mimic lignocellulosic hydrolysate feedstocks, with the best reverse-engineered xylose- and arabinose-metabolizing 4-coumarate producer significantly outperforming the reference strain.