Use of kefir-derived lactic acid bacteria for the preparation of a fermented soy drink with increased estrogenic activity

•Soy is a vegetal food rich in nutrients and a source of isoflavones.•The adaptation of kefir grains to a soy drink allowed the isolation of Leuconostoc strains.•Leuconostoc-fermented soy drink had a creamy texture and was free of flatus-causing sugars.•Fermentation with Leuconostoc enhanced the estrogenic activity of the soy drink.