Biotransformation of camu–camu galloylated ellagitannins by Lactiplantibacillus plantarum with extracellular tannase activity

Abstract

Some strains of Lactiplantibacillus plantarum produce specific tannases that could enable the metabolism of ellagitannins into more bioavailable phenolic metabolites, thereby promoting the health effects of these polyphenols. However, the metabolic ability of these strains remains poorly understood. In this study, we analyzed the ability of broad esterase-producing (Est_1092+) and extracellular tannase-producing (TanA+) strains to convert a wide assortment of ellagitannins from camu–camu (Myrciaria dubia) fruit. To this end, forty-three strains were screened to identify and sequence (WGS) those producing Est_1092. In addition, six previously reported TanA+ strains were included in the study. Each strain (Est_1092+ or TanA+) was inoculated into a minimal culture medium supplemented with an aqueous camu–camu extract. After fermentation, supernatants were collected for semi-quantification of ellagitannins and their metabolites by mass spectrometry. For analysis, the strains were grouped according to their enzyme type and compared with an Est_1092 and TanA-lacking strain. Out of the forty-three isolates, three showed Est_1092 activity. Of the Est_1092+ and TanA+ strains, only the latter hydrolyzed the tri-galloyl-HHDP-glucose and various isomers of HHDP-galloyl-glucose, releasing HHDP-glucose and gallic acid. TanA+ strains also transformed three isomers of di-HHDP-galloyl-glucose, liberating di-HHDP-glucose and gallic acid. Overall, TanA+ strains released 3.6–4.9 times more gallic acid than the lacking strain. In addition, those exhibiting gallate decarboxylase activity pursued gallic acid metabolism to release pyrogallol. Neither Est_1092+ nor TanA+ strains transformed ellagitannin-core structures. In summary, TanA+ L. plantarum strains have the unique ability to hydrolyze a wide range of galloylated ellagitannins, releasing phenolic metabolites with additional health benefits.