Effect of sporulation medium and its divalent cation content on the heat and high pressure resistance of Clostridium botulinum type E spores.

Clostridium (C.) botulinum type E belongs to the non-proteolytic physiological C. botulinum group II and produces the highly potent Botulinum neurotoxin E (BoNT/E) even at refrigerated temperatures. As C. botulinum type E spores are highly prevalent in aquatic environments, seafood and fishery products are commonly associated with this organism. Hydrostatic high pressure (HHP) treatments, or treatments combining HHP with elevated temperatures (HHPT), can be used to improve traditional preservation methods and increase food safety, quality and durability. In this study, we assessed the effect of different sporulation media and cation concentration on the heat resistance, HHP resistance, and HHPT resistance of spores from three C. botulinum type E strains. SFE (sediment fish extract) sporulation media yielded the most resistant spores, whereas, in M140 media, the least resistant spores were produced. Furthermore our results indicate that the divalent cation content (Ca(2+), Mg(2+) and Mn(2+)) plays a role in the differential development of C. botulinum type E spore resistance to heat, HHP and HHPT in different media. Calcium cations confer heat and HPPT resistance to spores, while high amounts of magnesium cations appear to have a negative effect. Manganese cations in low concentrations are important for the development resistance to HPP and HPPT treatments, but not heat alone. This study provides valuable information on the nature of non-proteolytic C. botulinum type E spores grown in different media. The data provided here can be useful to the food industry and to researchers when considering spore properties in food safety risk assessment and the experimental design of future inactivation studies.