Phospholipase C production of Listeria monocytogenes SLCC 5764 cultured with various salt concentrations, pHs, and temperatures

Abstract

Listeria monocytogenes SLCC 5764 was propagated at 4, 25, or 37°C in tryptic soy broth (TSB) containing 428, 787, or 1,112 mM NaCl; or adjusted with either acetic acid to pH 5.2, 5.7, or 7.0 or hydrochloric acid to pH 5.0, 5.7, or 7.0; or made alkaline with sodium hydroxide to pH 7.5, 8.5, or 9.5, to determine the effects on the production of phospholipase C (PLC). Altering the growth environment caused alterations in PLC production. The PLC activity was highest after cells were propagated in TSB containing 428 mM NaCl at each growth temperature. Little PLC activity was detected at 4 or 25°C in media with the lowest and highest salt concentrations. Similarly, little PLC activity was detected at 4 or 37°C at each pH from cells grown in media adjusted with either acid. The PLC activity was greater after the cells were grown in media adjusted with either acid at pH 7.0 at 25°C. For growth in alkaline media, the PLC activity was highest after the cells were propagated in media at pH 7.5 at each growth temperature.