The construction of new functional yogurt by probiotics lactic acid bacteria (LAB) with strong lactose hydrolyzing ability.

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Lactobacillus gasseri is known to be exist in human intestine, so the strain is widely used for the construction of functional yogurt as probiotics lactic acid bacteria (LAB) in Japan. In this study, it has been clarified the existence of three type of lactose hydrolyzing enzymes beta-galactosidae (β gal), phospho-beta-galactosidase (P β gal) and phospho-beta-glucosidase (P β glc) in LAB including L.gasseri. In this research, PbgA (phospho-beta-galactosidase A) was first isolated from L.gasseri ATCC33233^T and investigated by kinetics analysis. As the expression rate was very low for PbgB in the L.gasseri ATCC33233^T, we prepared the enzyme by expression with Lc.lactis subsp. cremoris and analyzed K_m and V_<max> values.We also investigated the adhesion activity of LAB to human colon mucin by a biocencer BIACORE which is one of most important requirement of probiotics. We could selected many adhesive LAB with high affinity to human mucin with ABO blood type A,B and O type.In the last stage of our research, to prevent the lactose intolerance in Japanese, we did mass-screening of LAB with high lactase activity from more than 200 strains of LAB isolated human intestine. Finally, we selected Lb. mucosae OLL2848,Lb. gasseri OLL2836 and Lb.gasseri OLL 2948 strains and constructed the new type of functional yogurt by using these three LAB strains.It was expected the decrease of symptoms of lactose intolerance especially to elderly peoples.