Germination-induced bioluminescence, a route to determine the inhibitory effect of a combination preservation treatment on bacterial spores

In this work, we have used spores of Bacillus subtilis that specifically in duce bioluminescence upon initiation of germination as a rapid, real-time m onitor of the effects of preservative treatments on germination. Using this tool, we have demonstrated that the combination of mild acidity (pH 5.5 to 5.0), lactic acid (0.5%), and a pasteurization step (90 degrees C for 5 mi n) results in enhanced inhibition of spore germination compared with the ef fects of the individual treatments alone. Inhibition by the combination tre atment occurred as a result of both direct but reversible inhibition, entir ely dependent on the physical presence of the preservative factors, and per manent, nonreversible damage to the L-alanine germination apparatus of the spore. However, we were able to restore germination of the preservative-dam aged spores unable to germinate on L alanine by supplementing the medium wi th the nonnutrient germinant calcium dipicolinic acid. The demonstration th at simple combinations of preservative factors inhibit spore germination in dicates that food preservation systems providing ambient stability could be designed which do not adhere to the strict limits set by commonly accepted processes and which are based on precise understanding of their inhibitory action.