from indigenous fermented foods and human gut ... - Thapar University

4.7.3 Resistance of Lactobacillus strains to 0.4% phenol
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Chapter IV: Results
Resistance to phenol was tested as an additional indicator for survival under intestinal
conditions (Xanthopoulos et al., 2000). Six probiotic candidate strains (L. casei LAM-1,
LAM-2, L. delbrueckii LKH-2, LKH-3, L. helveticus LKH-5 and L. fermentum Lamec-29
which survived the in vitro gastrointestinal passage as described above, were tested and
showed different degrees of sensitivity towards phenol. All L. casei strains were less sensitive
to phenol. Five of the six strains tolerated 0.4% phenol for 24 h, as their numbers did not
decrease (initial inoculum of approx. log 7.6 to 8.0). However, five of the strains were able to
grow in the presence of phenol during this incubation time (Table 4.15).
Table 4.15 Ability of Lactobacillus strains to grow in the presence of phenol 0.4% at
37°C
Viable count a (log10 CFU/ml)
Strains 0 h 24 h Increase b
MRS broth MRS broth + phenol 0.4%
0 h 24 h Increase b
LAM-1 7.95±0.06 10.09±0.02 2.14 8.05±0.14 8.75±0.34 0.70
LAM-2 8.17±0.16 10.65±0.07 2.48 8.12±0.13 8.52±0.40 0.40
LKH-2 8.09±0.04 9.88±0.11 1.79 7.98±0.43 8.64±0.51 0.66
LKH-3 7.87±0.10 8.87±0.24 1.00 8.05±0.08 8.63±0.09 0.58
LKH-5 7.07±0.03 7.29±0.12 0.22 7.40±0.11 7.42±0.02 0.02
Lamc-29 7.36±0.12 9.12±0.03 1.76 7.24±0.21 5.65±0.28 -1.59
a log mean counts of two trials (average ± s.d.),bincrease = log10(final population)-log10(initial population) n = 3; observations comes from three replicate
assays; data are represented as mean ± sd