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

tract, thus preventing them from adhering to IEC and also inhibiting them in this micro-
environment by producing organic acids, H2O2 and bacteriocin.
Competitive exclusion of two of the selected strains, i.e. L. casei LAM-1 and L. delbruckeii
LKH-2, was observed in vitro against representative food-borne pathogens, suggesting a
significant role in prevention of enteric infections.
After screening all six strains for their functional properties, strains displaying interesting
probiotic properties were then chosen for ability to produce bacteriocin. Amongst all, L. casei
LAM-1 elaborated a bacteriocin with wide spectrum of action (gram positive and negative food
borne pathogens) and stability under high temperature, pH and freeze thaw cycles. Most
probably, bacteriocin activity results from the sum of several factors; growth-associated and
stress associated mechanisms added to a possible constitutive production. According to the
derived polynomial as a function of pH, temperature and time of incubation, it can be observed
that production of bacteriocin by L. casei LAM-1 is regulated by different physiological factors.
The bacteriocin exhibited bactericidal activity through rapid loss of ATP and K + ions by
disruption of cell membranes of target pathogens; cell death was evidenced by live dead staining
and scanning electron microscopy followed by transmission electron microscopy.
It is recommended that colonization ability of the above mentioned probiotic isolates must
be further validated through in vivo studies. Overall, this study provides a rationale for the
further use of the selected L. casei LAM-1 and L. delbruckeii as probiotics for therapeutic and
preventive purposes; however a prior clinical trial in humans is mandatory. The application of
the bacteriocin from L. casei LAM-1for commercial purposes as biopreservative is also
suggested.
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