The present invention relates to a lactic acid bacterium isolated from human mothers milk, more precisely a Lactobacillus gasseri BNR17 strain that is isolated from Korean mothers milk and has excellent probiotic activity including acid resistance, bile acid resistance and antimicrobial activity and weight gaining inhibitory effect as well. Again, the Lactobacillus gasseri BNR17 of the present invention has excellent acid resistance, bile acid resistance, enteric absorption activity and antimicrobial activity against pathogenic microorganisms, in addition to the weight gaining inhibitory effect by synthesizing indigestible polysaccharides from monosaccharides included in food taken and releasing the synthesized polysaccharides out of the body. Therefore, the strain of the invention, owing to such beneficiary effects, can be effectively used not only for the production of fermented milk, other fermented food products and animal feeds but also for the production of live cell products and food additives for preventing weight gaining.
