The mechanism by which potassium sorbate inhibits Bacillus cereus T and
Clostridium botulinum 62A spore germination was investigated. Spores of B.
cereus T were germinated at 35°C in 0.08 M sodium-potassium phosphate buffers
(pH 5.7 to 6.7) containing various germinants (L-alanine, L-a-NH2-n-butyric acid,
and inosine) and potassium sorbate. Spores of C. botulinum 62A were germinated
in the same buffers but with 10 mM L-lactic acid, 20 mM sodium bicarbonate, Lalanine
or L-cysteine, and potassium sorbate. Spore germination was monitored
by optical density measurements at 600 nm and phase-contrast microscopy.
Inhibition of B. cereus T spore germination was observed when 3,900 jig of
potassium sorbate per ml was added at various time intervals during the first 2
min of spore exposure to the pH 5.7 germination medium. C. botulinum 62A spore
germination was inhibited when 5,200 ,ug of potassium sorbate per ml was added
during the first 30 min of spore exposure to the pH 5.7 medium. Potassium sorbate
inhibition of germination was reversible for both B. cereus T and C. botulinum
62A spores. Potassium sorbate inhibition of B. cereus T spore germination
induced by L-alanine and L-a-NH2-n-butyric acid was shown to be competitive in
nature. Potassium sorbate was also a competitive inhibitor of L-alanine- and Lcysteine-induced
germination of C. botulinum 62A spores.