Degradation of tannic acid by cell-free extracts of Lactobacillus plantarum

The ability of Lactobacillus plantarum CECT 748T to degrade hydrolysable tannins was evaluated. Three commercial tannic acids were incubated in presence of cell-free extracts containing soluble proteins from L. plantarum. By HPLC analyses, almost a complete tannic acid degradation was observed in the three samples assayed. By using HPLC-DAD/ESI-MS, we partially determined the composition of tannic acid from Quercus infectoria galls. This tannic acid is a gallotannin mainly composed of monomers to tetramers of gallic acid. We studied the mechanism of its degradation by L. plantarum. The results obtained in this work indicated that L. plantarum degrades gallotannins by depolymerisation of high molecular weight tannins and a reduction of low molecular weight tannins. Gallic acid and pyrogallol were detected as final metabolic intermediates. Due to the potential health beneficial effects, the ability to degrade tannic acid is an interesting property in this food lactic acid bacteria.