the present invention relates to microorganisms for the treatment or the prevention of obesity or diabetes mellitus , which reduce the amount of monosaccharide or disaccharide which may be absorbed into human body by converting monosaccharides such as glucose , fructose , galactose et al . and disaccharides into polymeric materials which cannot be absorbed by the intestine , and relates to a pharmaceutical composition containing the said microorganisms . preferred microorganisms are lactobacillus sp . bc - y009 and acetobacter sp . bc - y058 .