OPTIMIZATION OF LISTERIOLYSIN-O PRODUCTION BY LISTERIA-MONOCYTOGENES

Listeria monocytogenes serotype 1 and Scott A strains were examined to determine the effect of culture conditions on production of listeriol ysin O (LLO). The hemolytic activity was assayed by hemolysis of sheep red blood cells. The optimum pH range for LLO production in serotype 1 and Scott A were pH 6.2-6.0 and pH 5.8-6.0, respectively. Production of LLO by serotype 1 was 20-fold higher than by Scott A. Addition of more than 1.0% glucose significantly reduced production of LLO by the cells, while favoring growth. By adding 0.5% glucose after stationary phase and adjusting pH to 5.5-7.0, maximum LLO was produced after 2 h incubation at 37C by both strains.