Biosorption of copper by wine-relevant lactobacilli

Must and wine may be contaminated with elevated copper concentrations by the use of fungicides or in course of the vinification process. Hitherto only a few practicable and harmless procedures exist to reduce an excess of copper from must and wine. For this reason we investigated the biosorption of copper by eight wine-relevant Lactobacillus species. Both, living and heat-inactivated cells revealed a significant degree of Cu adsorption. It was shown that Cu binding correlated positively with an increasing pH value of the environment. The highest binding capacity of the tested lactic acid bacteria was found for L. buchneri DSM 20057 with a maximum of 46.17 μg Cu bound per mg cell in deionized water. In must, wine and grape juice Cu was removed less effective which is not solely attributed to low pH-values, but also to specific medium parameters such as intrinsic metal cations, organic acids or phenolic compounds. Nevertheless, about 0.5–1.0 μg Cu per ml could be removed from wine samples, which is sufficient enough to lower critical copper concentrations.