Recombinant proteins produced in Escherichia coli are often contaminated with endotoxins, which can be a serious problem for their further application. One of the possible solutions is the use of modified strains with reduced lipopolysaccharide (LPS) levels. We compared two approaches to engineering such strains. The first commonly known approach was modification of LPS biosynthesis pathway by knocking out seven genes in the E. coli genome. The second approach, which has not been previously used, was to increase expression of E. coli protein YciM. According to the published data, elevated expression of YciM leads to the reduction in the amount of the LpxC enzyme involved in LPS biosynthesis. We investigated the impact of YciM coexpression with eGFP on the content of endotoxins in the purified recombinant eGFP samples. Both approaches provided similar outcomes, i.e., decreased the endotoxin levels in the purified protein samples.
Keywords: CRISPR; Cas9; endotoxin; expression strain; lipid IVa; lipopolysaccharide; recombinant protein.