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The aims of this experiment was to isolate and identify LAB from infant
faeces and subsequent evaluation of its potential probiotics. LAB was isolated from
faeces of infants who consumed breast milk as the only source of diet on Lcysteine-
supplemented MRS Agar, and incubated on 37
o
C for 48 hours. Colonies
grew on this media were then identified based on cellular, physiological and
molecular approaches. Cellular and physiological identifications based on Gram
staining, motility, Catalase, CO2 and NH3 production, and the ability to grow on 10º
and 45ºC. Molecular identification relied on the amplification of sequence of 16S
rRNA . The potential application of selected isolates for probiotics was
evaluated based on the ability to grow on media with low pH and bile salts, the
ability to inhibit the growth of pathogenic Bacillus cereus and Escherrichia coli, to
utilize inulin as the only carbon source, and in vitro adherence ability. Cellular and
physiological identification resulted 17 isolates with lactic acid bacteria
characteristic. On the basis of analysis of 16S rRNA gene, the 1AF isolates were
classified as Lactobacillus casei. Evaluation of probiotic in vitro showed a growth
decreases of 39,56% viability after growing at pH 2.0 for 90 minutes. The growth
decline of isolates on the medium with the addition of 0.5% bile salts was 20,71%.
The selected isolate showed the ability to inhibit the growth of E. coli and Bacillus
cereus with inhibitory zone of 12,00±1,00 mm and 15,33±1,53 mm respectively.
Ability of attachment to the solid plate was 9.367±1721,43 colony/mm
2
. Growth
analysis of the selected isolates on a member of different carbon sources showed
the ability to grow normally on glucose, lactose, and sucrose as the only carbon
sources. Meanwhile, the growth of isolates on inulin as the only carbon sources was
slower than previously carbon sources. The data obtained had indicate that the
selected isolated isolates are of potential candidate as probiotic in vitro and able to
ferment inulin as the only carbon source.
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