A high prevalence of overweight and obesity has been observed in the past few decades in many countries. Overall, policies for production of healthier foods and environments are recommended for the prevention of obesity. Until recently, little action has been taken on this issue (Swinburn et al. 2013). It has been proposed that alterations in the composition of the gut microbiota known as dysbiosis may be related to the development of obesity (Neyrinck et al. 2012). The first goal of this study was to isolate the predominant bifidobacterium species from the stools of breast-fed infants, and to identify them by their 16S rRNA genes. The strains that were identified were B. longum subsp. longum FA1 and B. breve M4A. The survival rates measured six months after lyophilisation were 74.74% and 99.6% for B. longum subsp. longum FA1 and B. breve M4A, respectively.In a second step the growth of B. breve M4A and B. longum subsp. longum FA1 was examined in skimmed-milk media supplemented with different levels of yeast extract and in combination with glucose or oligofructose. These media increased the count of the strains after conservation by lyophilisation. Supplementation with glucose or oligofructose decreased the doubling time and increased the viable cell count. Factorial design showed a nonlinear relationship between skimmed-milk media, bacterial count number and acid production indicating an opposite impact of yeast extract with the supplementation of glucose or oligofructose in skimmed-milk media. Response surface plots were applied to optimize the supplemented skimmed-milk media. Both strains grew more rapidly in supplemented media than in the skimmed milkbased medium alone. The fermentation in skimmed milk was dependent on nutrient availability and the carbon source. The addition of yeast extract with glucose or oligofructose to skimmed milk increased the growth rate and acid production, compared with skimmed milk alone, when incubated anaerobically at 37°C for 48 hours. Acid production was higher in B. breve M4A than in B. longum subsp. longum FA1 when inoculated into skimmed milk supplemented with yeast extract with glucose or oligofructose.The second goal of the study was to evaluate the in vivo anti-obesity effect of B. breve M4A and B. longum subsp. longum FA1 in young mice fed an high-fat diet (HFD). Three (male mice C57BL/6JRj) groups, the model HFD group and treatment (HFD-FA1 and HFD-M4A) groups were fed an HFD to induce obesity. After feeding the mice a HFD for six weeks, animals receiving B. breve M4A (4.1 × 10_6 CFU/mL) and B. longum subsp. longum FA1 (2.9 × 10_6 CFU/mL) had significantly lower (p < 0.01) weight gain compared to mice fed a high-fat diet only. Mice fed B. breve M4A supplemented with 0.3% yeast extract and 3% glucose exhibited significantly lower serum triglycerides (p < 0.05) compared with the HFD group. The daily consumption (2.9×10_6 CFU/day) of B. longum subps. longum FA1 and (4.1×10_6 CFU/day) B. breve M4A (p < 0.01) significantly increased the amount of bifidobacteria and lactic acid bacteria in the large intestine.This study showed that Bifidobacterium species and their acid-production reduced weight gain and energy metabolism. Thus, bifidobacteria supplementation may be one mean for reducing obesity and related chronic Non-commuicable diseases.
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