A process for preparing a beverage or beverage component, the process comprising an enzymatic treatment of brewer's spent grain including addition of one or a combination of enzymes with alpha-amylase, gluco-amylase, cellulase, xylanase, protease and/or beta-glucanase activitiy and fermentation by a strain of lactic acid bacteria, the combination of enzymes and enzymatic treatment conditions are such that: said lactic acid bacteria produces 4.5 g/L lactic acid and metabolises sugar such that the resulting fermented broth contains less than 2.5% w/w, preferably less than 0.5% w/w residual sugar； or said lactic acid bacteria produces 4.5 g/L lactic acid and metabolises sugar such that the resulting fermented broth contains at least 2.5% w/w residual sugar.
