Abstract:Soybean contains high content of isoflavones such as genistein and daidzein, both can be converted to equol by intestinal microflora in human and animals. Equol may play an important role in human and animal health. Rodent species consistently produce high levels of equol, however, not all humans can produce equol. Equol-producing bacteria may be the key factors for this difference. Equol-producing bacteria may also have different equol-producing mechanism and capacity. In this paper, all equol-producing bacteria and their equol synthesis mechanism are reviewed, for further understanding the factors of equol-producing difference, the transformation of equol-producing ability, equol fermentation in vitro and applying to human clinical studies.