Isoflavones exhibit an estrogenic activity and have been reported extensively for their potential role in preventing chronic diseases, such as cancer, osteoporosis, and postmenopausal syndrome. Pueraria is a medicinally important leguminous plant producing several glycoside isoflavones, such as daidzin, daidzein, genistin, and puerarin. However, daidzin and genistin mainly exist as nonabsorbable and biologically inactive glycosides. The bioavailability of glucosides is increased by hydrolysis of the sugar moiety using β-glucosidase. Furthermore, intestinal microorganisms can enhance the biological activity of these isoflavones through biotransformation. Lactic acid bacteria (LAB) are typical probiotic microorganisms used in fermented foods, as feed additives, and in pharmaceuticals. Therefore, we isolated Lactobacillus rhamnosus BHN-LAB 76 from Korean traditional fermented food and assessed its isoflavone-transforming activity in the production of daidzein using HPLC. The Pueraria lobata extract was fermented with L. rhamnosus BHN-LAB 76 for 72 h at 37℃ under anaerobic conditions. L. rhamnosus BHN-LAB 76 could convert about 25% of daidzin to daidzein. These results confirmed the potential of L. rhamnosus BHN-LAB 76 as a probiotic culture, which can be utilized in the manufacture of fermented and functional foods.