Water kefir as a promising low-sugar probiotic fermented beverage

Background Water kefir is a slightly sweet, acidic, fruity, sparkling, and slightly alcoholic fermented beverage produced with water kefir grains, the latter consisting of polysaccharides and micro-organisms. The micro-organisms involved in water kefir fermentation comprise yeast, lactic acid bacteria, bifidobacteria, and acetic acid bacteria. Some strains of micro-organisms in water kefir might possess probiotic activity. Also, water kefir is a beverage with relatively low sugar content, providing an interesting alternative to sugary soft drinks. To be able to exploit water kefir for its probiotic potential or as a low-sugar soft-drink, in-depth research is needed to unravel the species diversity and community dynamics of water kefir fermentation. In particular, substrate consumption and metabolite production in water kefir have not been studied until now.