Quantitative insights on the interaction between metal ions and water kefir grains: kinetics studies and EPR investigations

Water kefir is an acid, softly alcoholic and fragrant beverage fermented by a stable consortium of multispecies microbial community. Aim of this study was to investigate the ability of water kefir grains to abate significant amounts of heavy metal ions during the preparation of the water kefir beverage and to set up an experimental and analytical methodology based on ICP-OES spectroscopy and ionic chromatography for the evaluation of heavy metal bioaccumulation by water kefir grains. We investigated the absorption kinetics of the process. The use of EPR spectroscopy enabled us to characterize the interaction between water kefir grains and paramagnetic metal ions from the structural viewpoint. Our results highlight significant differences in both the kinetics and the structural aspects of the interaction between distinct metal ions and water kefir grains. They concur clarifying the potential role of water kefir grains as detoxifying agents towards heavy metal ions.