Zinc Uptake by Lactic Acid Bacteria

The study aims to investigate zinc biosorption by strains of lactobacilli and bifidobacteria with a view to exploit them as organic matrixes for zinc dietary supplementation. Sixteen human strains of Lactobacillus and Bifidobacterium were assayed for zinc uptake. The minimum inhibitory concentration of zinc salts differed among the strains, but was never below 15 mmol L(-1). When cultured in MRS broth containing 10 mmol L(-1) ZnSO4, all the strains were capable of accumulating zinc in the range between 11 and 135 μmol g(-1). The highest amount of cell-bound zinc was obtained in L. acidophilus WC 0203. pH-controlled batch cultures of this strain revealed that zinc uptake started in the growth phase, but occurred mostly during the stationary phase. Pasteurized and viable cultures accumulated similar amount of zinc, suggesting that a nonmetabolically mediated mechanism is involved in zinc uptake. These results provide new perspectives on the specific use of probiotics, since L. acidophilus WC 0203 could function as an organic matrix for zinc incorporation. The bioavailability of Lactobacillus-bound zinc deserves to be investigated to provide a future basis for optimization of zinc supplementation or fortification.