Enhancing translation efficiency and exploring constraints in high-level 4-hydroxyvaleric acid production from levulinic acid in Escherichia coli

4-Hydroxyvaleric acid (4-HV) holds promise as a sustainable monomer for biodegradable polyesters and liquid transportation fuels. This study achieved high-level 4-HV production from levulinic acid using an antibiotic-free, substrate-inducible system in Escherichia coli. Enzymes involved in the conversion of levulinic acid to 4-HV were expressed with a bicistronic design of ribosome binding sites. The engineered strain demonstrated a 28