Genome-scale metabolic model guided metabolic flux analysis in the endophyte Alternaria burnsii NCIM1409

Camptothecin (CPT), a potent anticancer alkaloid, is traditionally derived from plants like Camptotheca acuminata and Nothapodytes nimmoniana, but sustainable production remains challenging. This study explores the metabolic network of the fungal endophyte Alternaria burnsii NCIM1409, known for camptothecin production, using genome sequencing, genome scale metabolic modeling, and 13C-based pathway mapping. A genome-scale metabolic model (AltGEM iDD1552) was reconstructed, comprising 2188 reactions, 2148 metabolites, and 1552 genes, along with manual curation to include camptothecin biosynthesis pathways. Flux balance analysis identified key enzymatic targets, including secologanin synthase and tryptophan decarboxylase, for enhancing CPT production. Further, metabolic analysis of A. burnsii subjected to 20%[U-13C6] glucose or 99% [1-13C] glucose revealed active glycolysis, the pentose phosphate pathway, and the TCA cycle. This integrative approach provides insights into A. burnsiis metabolic capabilities and highlights strategies for optimizing camptothecin biosynthesis, offering a foundation for sustainable production methods.