Figure 2From: Production and purification of high molecular weight oligomers of Yersinia pestis F1 capsular antigen released by high cell density culture of recombinant Escherichia coli cells carrying the caf1 operonPurification process of rF1 antigen. (1) Fermentation culture supernatant. (2) 0.2 μm micro-filtration filtrate. (3) 50 kDa ultra-filtration retentate. (4) 33% ammonium sulfate precipitate. (5) Flow-through of Superdex-200 size-exclusion chromatography. (6) Y. pestis F1 standard.Back to article page