Tannin Degradation by a Novel Tannase Enzyme Present in Some Lactobacillus plantarum Strains

Lactobacillus plantarum is frequently isolated from the fermentation of plant material where tannins are abundant. L. plantarum strains possess tannase activity to degrade plant tannins. An L. plantarum tannase (TanB(Lp,) formerly called TanLp1) was previously identified and biochemically characterized. In this study, we report the identification and characterization of a novel tannase (TanA(Lp)). While all 29 L. plantarum strains analyzed in the study possess the tanB(Lp) gene, the gene tanA(Lp) was present in only four strains. Upon methyl gallate exposure, the expression of tanB(Lp) was induced, whereas tanA(Lp) expression was not affected. TanA(Lp) showed only 27% sequence identity to TanB(Lp), but the residues involved in tannase activity are conserved. Optimum activity for TanA(Lp) was observed at 30 degrees C and pH 6 in the presence of Ca2+ ions. TanA(Lp) was able to hydrolyze gallate and protocatechuate esters with a short aliphatic alcohol substituent. Moreover, TanA(Lp) was able to fully hydrolyze complex gallotannins, such as tannic acid. The presence of the extracellular TanA(Lp) tannase in some L. plantarum strains provides them an advantage for the initial degradation of complex tannins present in plant environments.