engleski

The effect of metal ions supplementation on growth and binding capacity of lactic acid bacteria

INTRODUCTION The resistance to metal ions and metal ions binding capacity of different microorganisms is the basis of their usage in biotechnology processes. The lactic acid bacteria (LAB) are non-pathogenic, food safe microorganisms, which are commonly applied in food industry where they are often exposed to metal ions. The interactions between LAB and metal ions are very poorly investigated. Because of that, the influence of Zn, Cu and Mn on growth, acid production and binding capacity of wild and adapted strains of Leuconostoc mesenteroides, Lactobacillus brevis and Lactobacillus plantarum was investigated in this work. METHODOLOGY The wild LAB strains and LAB strains adapted to high concentrations of metal ions were exposed to various concentrations of metal ions in the MRS medium in static and dynamic conditions. The effect of metal ions supplementation on LAB growth, acid production and metal ions accumulation was monitored. RESULTS AND DISCUSSION The Zn and Mn supplementation in the investigated concentrations did not have effect on the bacterial growth and acid production while copper ions were highly toxic, especially in static conditions. The adaptation had a positive effect on the growth and acid production of all bacterial species in the presence of copper. However, the adapted strains of bacteria incorporated less metal ions than the wild strains. The exception was adapted bacteria L. brevis that accumulated high concentration of copper ions in static conditions. The difference in copper binding mechanism between species and between wild and adapted cells was investigated by 2D SDS-PAGE. CONCLUSIONS The results have shown that the presence of metal ions in the growth medium can influence growth and acid production of tested LAB. The effect is dependent on variety of metal ions and LAB species. Among the chosen LAB strains Leuc. mesenteroides was the most efficient in Zn binding processes, while L. plantarum accumulated high tested concentration of Mn. L. brevis was the most copper resistant.

metal ions; lactic acid bacteria

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