Antibacterial activity and probiotic properties of some lactic acid bacteria isolated from dairy products

Several lactic acid bacteria strains were screened for the production of antibacterial substances active against some pathogenic bacteria. The inhibitory mechanism was investigated and was shown to be dependant of bacteriocin production. The objective was to isolate LAB with antibacterial activity from raib and to select strains that could be used for the determination of probiotic properties. Results showed that 6 LAB cultures retained activity in the supernatants after neutralization and catalase treatment. Streptococcus thermophilus T2 strain showed the wide inhibitory spectrum against the Gram positive bacteria. Growth and bacteriocin production profiles showed that the maximal bacteriocin production by S. thermophilus T2 cells was measured by the end of the late-log phase (90 AU ml−1) with a bacteriocin production rate of 9.3 (AU ml-1 h-1). In addition, our findings showed that the bacteriocin, produced by S. thermophilus T2, was stable over a wide pH range (4 - 8), indicating that such bacteriocin may be useful in acidic as well as non acidic food. This preliminarily work shows the potential application of autochthonous lactic acid bacteria to improve safety of traditional fermented food. Around 40% of these strains, mainly isolated from Algerian fermented milks in MRS agar, were pre-selected for testing as potential probiotics by their ability to grow adequately at low pH values. In vivo study indicates that number of Sc T2 and Lb. B2 remains important as long as rabbits consume some fermented products. Antibacterial activity of Lactobacillus and Streptococcus against indicator bacteria is a good probiotic property. Transfer of these antimicrobial activities to in vivo conditions is beneficial for the maintenance of the intestinal microflora.Keywords: Bacteriocin, lactic acid bacteria, Streptococcus thermophilus. Lactobacillus bulgaricu, probioticAfrican Journal of Biotechnology Vol. 12(20), pp. 2949-295

Antibacterial Activity of Some Lactic Acid Bacteria Isolated from an Algerian Dairy Product

In the present study, the antibacterial effect of 20 lactic acid bacteria isolates from a traditional cheese was investigated. 6 isolates showed antibacterial effect against Gram positive bacteria. Streptococcus thermophilus T2 strain showed the wide inhibitory spectrum against the Gram positive bacteria. Growth and bacteriocin production profiles showed that the maximal bacteriocin production, by S. thermophilus T2 cells, was measured by the end of the late-log phase (90 AU ml−1) with a bacteriocine production rate of 9.3 (AU ml−1) h−1. In addition, our findings showed that the bacteriocin, produced by S. thermophilus T2, was stable over a wide pH range (4–8); this indicates that such bacteriocin may be useful in acidic as well as nonacidic food. This preliminarily work shows the potential application of autochthonous lactic acid bacteria to improve safety of traditional fermented food

Association of carob galactomannans with probiotic bacteria in synbiotic fermented milk and colon targeted-release carrier

International audienceFor the first time, this study presented the use of raw locust bean gum (LBG) as a prebiotic, with one probiotic strain in synbiotic fermented milk or combined with Na-alginate as a biopolymer, for a targeted release of bacteria under colon-like conditions. For this purpose, the fermentative characteristics (biomass, pH), bacterial survival, and developed viscosities of the stored fermented milks were determined. The survival rates of microencapsulated bacteria using the emulsion technique under simulated gastrointestinal conditions (stomach: pH 2 + 0.3% pepsin; colon: pH 6.5 + 1% pancreatin + 0.3% bile) were also evaluated. Results showed that all the tested bacteria maintained better biomass and acidifying activities in the presence of LBG, especially at 2%. During cold storage, the viscosities of the LBG-fermented milks were regulated and better appreciated, especially at 2%. Lactobacillus rhamnosus LbRE-LSAS and Bifidobacterium animalis subsp. lactis Bb12 microencapsulated separately in Ca-alginate-raw carob gum maintained good survival rates (51 - 66%) as compared to free cells (21 - 59%) under simulated digestive conditions, and were released under colon-like conditions. Therefore, the formulation of LBG-enriched fermented milks containing probiotic bacteria could represent a very good candidate for industrial application. Ca-alginate-raw LBG beads for the specific release of probiotics in the colon could benefit consumers with celiac disease or other digestive disorders because LBG is naturally gluten-free

Long term ingestion of a preload containing fructo-oligosaccharide or guar gum decreases fat mass but not food intake in mice

Fermentable dietary fibre such as fructo-oligosaccharide and viscous dietary fibers such as guar gum and alginate affect energy homeostasis. The goal of this study was to compare the impact of long term intake of these three dietary fibers on food intake, meal pattern, body weight and fat accumulation in mice. Over a period of 3 weeks, the-mice were fed daily with a preload containing 32 mg of fructo-oligosaccharide or alginate or 13 mg of guar gum. Food intake and body weight were monitored weekly, while meal patterns, adiposity and the expression of hypothalamic neuropeptide genes were evaluated at the end of the study period. The 3 dietary fibers produced a similar decrease in total daily food intake (14 to 22%) at the end of the first week, and this effect disappeared over time. The 3 dietary fibers induced a slight variation in satiation parameters. Body weight and expression of hypothalamic neuropeptide genes were not affected by any of the treatment. Preload of fructo-oligosaccharide and guar gum induced a similar and substantial decrease in the development of adiposity (17% and 14%, respectively), while alginate had no effect. Our results demonstrate mainly that the inhibitory effect of dietary fiber on food intake is lost over time, and that guar gum limits fat storage

Fructo-oligosaccharides reduce energy intake but do not affect adiposity in rats fed a low-fat diet but increase energy intake and reduce fat mass in rats fed a high-fat diet

International audienceThe ingestion of low or high lipid diets enriched with fructo-oligosaccharide (FOS) affects energy homeostasis. Ingesting protein diets also induces a depression of energy intake and decreases body weight. The goal of this study was to investigate the ability of FOS, combined or not with a high level of protein (P), to affect energy intake and body composition when included in diets containing different levels of lipids (L). We performed two studies of similar design over a period of 5 weeks. During the first experiment (exp1), after a 3-week period of adaptation to a normal protein-low fat diet, the rats received one of the following four diets for 5 weeks (6 rats per group): (i) normal protein (14% P/E (Energy) low fat (10% L/E) diet, (ii) normal protein, low fat diet supplemented with 10% FOS, (iii) high protein (55%P/E) low fat diet, and (iv) high protein, low fat diet supplemented with 10% FOS. In a second experiment (exp2) after the 3-week period of adaptation to a normal protein-high fat diet, the rats received one of the following 4 diets for 5 weeks (6 rats per group): (i) normal protein, high fat diet (35% of fat), (ii) normal protein, high fat diet supplemented with 10% FOS, (iii) high protein high fat diet and (iv) high protein high fat diet supplemented with 10% FOS. In low-fat fed rats, FOS did not affect lean body mass (LBM) and fat mass but the protein level reduced fat mass and tended to reduce adiposity. In high-fat fed rats, FOS did not affect LBM but reduced fat mass and adiposity. No additive or antagonistic effects between FOS and the protein level were observed. FOS reduced energy intake in low-fat fed rats, did not affect energy intake in normal-protein high-fat fed rats but surprisingly, and significantly, increased energy intake in high-protein high-fat fed rats. The results thus showed that FOS added to a high-fat diet reduced body fat and body adiposity