An Escherichia coli Strain for Plasmid DNA Production with a Low Endotoxin Level

Plasmid DNA (pDNA) is one of the possible types of vectors used in gene therapy. Escherichia coli is the most common bacterium for the production of pDNA. Lipopolysaccharides are the main component of the outer membrane of E. coli. Lipopolysaccharides are strong endotoxins, and their presence in pharmacological substances is highly undesirable. One of the approaches to eliminating endotoxin contamination of target substances is knocking out the genes of the lipopolysaccharide biosynthesis pathway. Using the CRISPR/Cas9 genome editing technology, we obtained a mutant form of the E. coli strain SCS110. We knocked out the genes kdsD, gutQ, lpxM, lpxL, lpxP, pagP, and eptA. As a result, lipopolysaccharide contamination of pDNA samples isolated by different methods from the mutant E. coli SCS 110 was significantly lower (19 to 295 times) than in pDNA samples from the original strain.