THE EFFECT OF THE PH OF THE SPORULATION ENVIRONMENT ON THE HEAT-RESISTANCE OF CLOSTRIDIUM-PERFRINGENS SPORES

The inactivation of Clostridium perfringens NCTC 8239 spores at 95° and 105° C, as determined by colony formation on an agar base containing lysozyme (BASE + lysozyme), was influenced by the initial pH of the sporulation medium. In the pH range of 7.0-8.5, established by the addition of each of several biological buffers or carbonate buffer to Duncan-Strong (DS) medium, increased pH resulted in formation of spores with greater resistance to inactivation at elevated temperatures. An increase of pH from 8.5 to 9.0 resulted in increased resistance of spores formed in DS-carbonate but not DS-TAPS (N-tris[hydroxymethyl]methyl-3-aminopropanesulfonic acid) medium. Resistance to spore injury, as determined by reduced recovery on BASE compared with BASE + lysozyme, was not increased for spores formed in media with higher pH's. As the pH of the medium increased, cell growth and number of spores formed were decreased, but the percentage of sporulation was apparently not affected. © 1990 Springer-Verlag New York Inc.