Hemolysin proteins are exotoxins produced by bacteria that can cause lysis of red blood cells in vitro. Hemolysin E is a pore-forming hemolysin, one of three types of hemolysin. Generally, hemolysin E is not expressed under standard growth conditions such as growth in LB medium at $37^{circ}C$. However, in E. coli, when the hns gene, which encodes H-NS, a global regulatory DNA binding protein, is knocked out, hemolysin E gene is expressed. Because hns genes in E. coli and K. pneumoniae are similar, K. pneumoniae UN strain hns gene was knocked out in this research. The hns knockout mutant of K. pneumoniae UN is found to produce a 19 kDa hemolysin protein and shows hemolytic activity.