The acid tolerance profile of L. fermentum SK5 (Fig. 2A) showed that after 1 h at every tested pH there was virtually no effect on cell numbers, after 2 h therewas virtually no viable cells left at pH 2 but with little change in numbers at pH 3, and after 3 h numbers fell to only 96.57% at pH 3 with again no change at pH 4. As for resistance to bile salts (oxgall) in PBS (Fig. 2B) no viable L. fermentum SK5 cells were detected after exposure to 0.3 and 0.4% bile salts for 2 h. Exposure to 0.2% oxgall over 4 h reduced cell numbers gradually by about 30% and exposure to 0.1% oxgall over 4 h reduced numbers by only 8.5%.
The resistance of L. fermentum SK5 to pepsin and pancreatin is
shown in Fig. 2C and D, respectively. When exposed to pepsin (SGF)
there was still more than 99% survival at pH 3 and 4 after 3 h but at
pH 2 the survival rate was decreased to only 70.48% whereas in the
absence of pepsin at pH 2 all cells died. Exposure to pancreatin (SIF)
at either pH 6.8 or 8 had virtually no effect on viable cell numbers.