Identification of the orange pigment in Nonomuraea gerenzanensis and development of a pigment-free mutant

The secondary metabolite A40926, a precursor to the glycopeptide antibiotic dalbavancin, is synthesized by the rare actinomycete Nonomuraea gerenzanensis (N. gerenzanensis) within the pharmaceutical industry. The biosynthesis of A40926 is accompanied by the production of an orange pigment, which poses significant challenges and incurs high costs in the purification process of A40926. To identify this orange pigment, a comprehensive analysis was conducted, including the examination of the biosynthetic gene cluster, potential biosynthetic pathways, purification processes, and structural identification. Additionally, the ispF gene, which encodes the enzyme 2-C-methyl-D-erythritol 2,4-cyclodiphosphate synthase and is implicated in the biosynthesis of orange pigment, was deleted using the CRISPR/Cas9 system. To enhance A40926 production in the ΔIspF mutant, the overexpression of the cyclic AMP receptor protein (Crp) was implemented to assess its regulatory impact on A40926 biosynthesis. Consequently, the orange pigment produced by N. gerenzanensis was identified as lycopene, synthesized via the methylerythritol phosphate (MEP) pathway. Although the ΔIspF mutant was unable to biosynthesize the orange pigment, its production of A40926 was adversely affected and was lower than that of the original strain. Consequently, the overexpression of the global regulator Crp significantly enhanced A40926 production, achieving a yield of 841.1 mg/L. The investigation of pigment-free mutants presented in this study offers valuable insights for effectively reducing production costs within the microbial pharmaceutical industry.