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

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Chapter I: Introduction
thermophilus to make yoghurt, is unable to colonize the bowl and is not isolated in the feces
(Finegold et al., 1977).
The human gastrointestinal tract is known to possess active clearance mechanisms
for microorganisms, and has proven difficult to introduce new bacterial strains into this
ecosystem (Savage, 1979; Paul and Hoskins, 1972). However, in different circumstances it
can be beneficial to alter the intestinal microflora by introducing lactobacilli. The nutritional
and therapeutic benefits derived from this approach have been discussed by Gorbach (1990),
and the claimed benefits of bacterial supplementation include increased nutrient utilization,
alleviation of lactose intolerance, treatment of hepatic encephalopathy and intestinal
infections, and inhibition of bacterially derived generation of carcinogens in the intestinal
tract (Finegold et al., 1977).
Lactobacillus spp.
Lactic acid bacteria constitutes group of bacteria which cause fermentation and
coagulation in milk and produce lactic acid from lactose. The family name Lactobacteriaceae
was coined by Orla-Jensen (1919) for a physiological group of Gram-positive rods and cocci.
They are anaerobic bacteria, non-sporulating, acid tolerant and produce mainly lactic acid as
an end product of carbohydrate fermentation. On the basis of end product of their
fermentation they can be divided into different genera which include homofermenters and
heterofermenters. The homofermenters produces lactic acid as the major product of
fermentation of glucose and include the genera Lactococcus, Streptococcus and Pediococcus.
In contrast, the heterofermenters produce a number of by-products along with lactic acid,
such as carbon dioxide, acetic acid, and ethanol from the fermentation of glucose and
includes the genus Leuconostoc and a subgroup of the genus Lactobacillus, the Betabacteria
(Kandler et al., 1986; Schillinger and Lücke, 1987). Members of Lactobacillus spp. are