Endospores of Bacillus spp. release DPA during thermal treatments or high temperature/high pressure treatments at 98
Ce
140
C, and measurement of DPA release was proposed as a rapid
screening tool for the heat resistance of Bacillus endospores (Kort
et al., 2005; Margosch et al., 2004a). However, pressure-induced
release of DPA from endospores of C. botulinum was observed only
after inactivation of more than 90% of the endospore population
(Margosch et al., 2004b). Release of DPA from C. beijerinckii and
C. sporogenesendospores at 90
C in this study was quite comparable
(30 and 50% loss of DPA, respectively, after 60 min treatments).
However, sporicidal effects of the same treatments differed by 4 log
(cfu g1
). The current results do not support the use of DPA release
profiles as a measure of endospore inactivation for comparison
between strains. However, they do allow for intra-strain comparison
of the effects of high temperature or high temperature/high pressure
on endospore inactivation. C. sporogenes and C. beijerinckii endospores released DPA after treatment at 90
C and 600 MPa with or
without antimicrobials; these treatments also permeabilised
endospore walls to DAPI. Treatments at 90
C without nisin did not
allow access of DAPI to the endospore cytoplasm, and did not result
in an appreciable DPA release. The effect of nisin on endospore
permeability to DAPI corresponded to its effect on DPA release and
spore inactivation, and indicates pore formation in membranes of
resting spores
Endospores of Bacillus spp. release DPA during thermal treatments or high temperature/high pressure treatments at 98
Ce
140
C, and measurement of DPA release was proposed as a rapid
screening tool for the heat resistance of Bacillus endospores (Kort
et al., 2005; Margosch et al., 2004a). However, pressure-induced
release of DPA from endospores of C. botulinum was observed only
after inactivation of more than 90% of the endospore population
(Margosch et al., 2004b). Release of DPA from C. beijerinckii and
C. sporogenesendospores at 90
C in this study was quite comparable
(30 and 50% loss of DPA, respectively, after 60 min treatments).
However, sporicidal effects of the same treatments differed by 4 log
(cfu g1
). The current results do not support the use of DPA release
profiles as a measure of endospore inactivation for comparison
between strains. However, they do allow for intra-strain comparison
of the effects of high temperature or high temperature/high pressure
on endospore inactivation. C. sporogenes and C. beijerinckii endospores released DPA after treatment at 90
C and 600 MPa with or
without antimicrobials; these treatments also permeabilised
endospore walls to DAPI. Treatments at 90
C without nisin did not
allow access of DAPI to the endospore cytoplasm, and did not result
in an appreciable DPA release. The effect of nisin on endospore
permeability to DAPI corresponded to its effect on DPA release and
spore inactivation, and indicates pore formation in membranes of
resting spores
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