The inhibitory potential of LAB culture supernatants against
indicator bacteria was studied to detect extra-cellular inhibitors.
Supernatants of LAB cultures were transferred (10%: v/v) into NB
inoculated with indicator bacteria (109 cfu ml1) which had grown
for 24 h at 37 C. The indicator cultures, with and without LAB
supernatants (control), were incubated aerobically at 37 C for 48 h.
Samples were collected at 0, 24 and 48 h for enumeration by colony
count based on 10 fold serial dilutions, where 100 ml of appropriate
dilutions of each culture were spread (depending on indicator organism
used) on: B. cereus selective agar (PEMBA; Oxoid CM0617
with added egg yolk SR47 and polymixin B SR99), Baird Parker (BP;
Oxoid CM0275 with added egg yolk tellurite supplement SR54),
Xylose Lysine Deoxycholate agar for Salmonella species (XLD, Oxoid
CM0469) and MacConkey agar (Mac; Oxoid CM0007) for E. coli. All
plates were incubated at 37 C for 48 h.