Increasing the bioavailability of soy isoflavones using lactic acid bacteria

Abstract

Interest in soybeans and soy-based products has grown significantly in the last decade due to their reported nutritional and health-promoting benefits. Researchers have credited phytochemicals in soybeans, especially isoflavones, for some of these beneficial health effects. Soy isoflavones are reported to play a role in the prevention of osteoporosis, cardiovascular disease, and several hormone dependent cancers. Soybean and soy foods contain isoflavones which are found as a complex mixture of glucoside conjugates the most abundant being the glucosides of genistein and daidzein, known as genistin and daidzin. In the case of soymilk, isoflavones are present as either aglycones or glucosides depending on the soy source used in manufacture (raw soybean or soy protein isolate). The metabolic fate of soy isoflavones after consumption, as well as their biological activities depends on their chemical structure.In order to exert a biological effect, isoflavone glucosides are hydrolyzed by both intestinal mucosal and bacterial beta-glycosidase releasing the aglycones. Several studies have demonstrated that lactic acid bacteria with beta-glucosidase activity are able to increase the aglycone content during soymilk fermentation. This chapter will discuss the use of Lactic Acid Bacteria that produce beta-glucosidase in order to improve the bioavailability of soy isoflavones.