Bio-Based Production of Uroporphyrin and Protoporphyrin-IX in Escherichia coli

Abstract

Porphyrins are tetrapyrrole compounds with diverse medical applications but challenging chemical and biological synthesis. This thesis reports a novel bioprocess approach for enhanced production of porphyrins including uroporphyrin (UP) and protoporphyrin IX (PP-IX) in Escherichia coli (E. coli) through the implementation of the C4/Shemin pathway. We first heterologously implemented the C4/Shemin pathway in an E. coli strain with an enlarged intracellular succinyl-CoA pool. Using plasmids with trc and gracmax promoters regulating the expression of synthesized gene operons, we characterized the effects of key pathway genes (hemA, hemB, hemC, hemD, hemE, and hemF, and hemG) on UP and PP-IX biosynthesis. By cultivating the resulting engineered E. coli strains in a glycerol-fed batch bioreactor under aerobic conditions, we produced up to 901.9 mg/L UP and 64.7 mg/L PP-IX. This thesis demonstrates the utility of synthetic biology and metabolic engineering strategies for large-scale bio-based production of UP and PP-IX.