Even with many new experimental molecular
identification techniques and with the known problem of
database accuracy and consistency over time, sequence
analysis of 16S rRNA is the major molecular technology
presently available for microbial identification [17].
Table 2 shows the identification scheme for LAB 18
and 48 using the MIDI System Identification (from
two laboratories), the Biolog Identification System and
16S rRNA Sequence Analyses. The results showed that
identification of these strains is difficult; nevertheless, the
use of defined cultures for probiotic use is still safer than
undefined cultures.
Resistance to pH, temperature, and sodium chloride
The first host factors that may affect commercial
probiotics are the high acidity in the proventriculus and
ventriculus and the high concentration of bile components
in the proximal intestine [5, 18]. Therefore, being
tolerant to acidic conditions is an important criterion to
be considered during the selection of potential probiotic
isolates to assure their viability and functionality.
Moreover, probiotic bacteria show variable resistance to
acidic conditions, and this characteristic is species and
strain dependent [4]. LAB 18 and 48 did not survive
an incubation period of 2 or 4 hr at pH 2.0. However,
at a pH of 3.0, both strains were resistant after 2 and 4
hr of incubation (Table 3). As reported by Fontana et al.
[4], Lactobacillus spp. isolates have been shown to be