Synthesis of 4-hydroxybenzoic Acid in Escherichia coli by a Modular co-culture System

Advancements in metabolic engineering and synthetic biology have enabled microbial production of an extensive range of valuable chemicals. Traditionally, a single microbial strain is used in these processes. However, the integration of complex, multi-layered regulatory mechanisms within metabolic pathways imposes a significant metabolic burden on host cells. To address these challenges, modular co-culture strategies have garnered increasing attention. In this study, we constructed a modular co-culture system to produce 4-hydroxybenzoic acid (4-HBA), which has applications across diverse fields, including food, medicine, and cosmetics. The complete 4-HBA synthesis pathway was segmented into upstream and downstream modules at the shikimic acid node, with each module constructed in separate Escherichia coli strains. During modular co-culture of the upstream and downstream strains, the maximum production titer of 4-HBA reached 0.928 g/L when the initial inoculation ratio of upstream to downstream strains was 2:1. This study represents the first report of 4-HBA synthesis using glucose as the sole carbon source through modular co-culture technology, thereby expanding the application scope of this technology and providing a valuable reference for microbial production of 4-HBA.