Abstract
This study is related to the isolation and identification of strains of local thermophilic lactic acid bacteria belonging to the species, Streptococcus thermophilus andLactobacillus bulgaricus. These bacteria can exist under extreme conditions of the digestive tract (acidity and high concentration of bile salts) and have a high capacity to degrade lactose. The aim is to produce yoguort with the bacteria that remain viable and active in the digestive tract, so as to enhance lactase activity at the intolerant lactose. The results also show considerable variations between genera, species and strains of the same species in the decomposition of lactose in pure and mixed cultures (Sc.t5 and Sc.t3, respectively, with 48 and 42%) (YSLB2, YSLB4and YSLB1, respectively, with 90.44, 87.22 and 84.28%) of initial lactose after 6 h of incubation at 37°C while keeping a level of viability higher than 107 cells/ ml. In the presence of pH (2.5, 4.5 and 6.5), put with or without 0.3% of bile salts, the results are also unmatched. The best cultures will be used to manufacture fermented milks (yoghurts) in order to correct intolerance with lactose in man after having to test them, in a second part, in vivo. Key words: Lactic acid bacteria, extremophile, intolerance of lactose, digestive tract.
Highlights
The lactose is a diholoside present in significant quantity in the milk of mammals
Dried milk used is of commercial nomination CELIA (France), containing 38.34 g/L lactose; this content is a useful reference for the calculation of the amount of lactose degraded by the bacteria in pure and mixed cultures
According to Drouault et al (2002), Streptococcus salivarius ssp. thermophilus is able to produce an active galactosidase during the intestinal transit time
Summary
The lactose is a diholoside present in significant quantity in the milk of mammals. In human digestive tract, it is degraded by intestinal lactase ( galactosidase) to glucose and galactose.Approximately, 70% of the adult world population shows a lactase deficiency, which is the cause of digestive disorders when they ingest milk. The lactose is a diholoside present in significant quantity in the milk of mammals. It is degraded by intestinal lactase ( galactosidase) to glucose and galactose. 70% of the adult world population shows a lactase deficiency, which is the cause of digestive disorders when they ingest milk. The reduction of the excessive lactose rates in the intestine can decrease the risks of these disorders (distension, diarrheas, vomiting, etc) (Cerf-Bensussan, 2002). The modulation of the lactasic activity, due to the digestion of lactose in yoghourt is carried out by bacterial enzymes, including the galactosidase which converts glucose to galactose during the transit in the digestive tract (Drouault et al, 2002)
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