Proteomic characterization of a selenium‐metabolizing probiotic <i>Lactobacillus reuteri</i> Lb2 BM for nutraceutical applications

Abstract

Abstract Selenium (Se), Se‐cysteines and selenoproteins have received growing interest in the nutritional field as redox‐balance modulating agents. The aim of this study was to establish the Se‐concentrating and Se‐metabolizing capabilities of the probiotic Lactobacillus reuteri Lb2 BM, for nutraceutical applications. A comparative proteomic approach was employed to study the bacteria grown in a control condition (MRS modified medium) and in a stimulated condition (4.38 mg/L of sodium selenite). The total protein extract was separated into two p I ranges: 4–7 and 6–11; the 25 identified proteins were divided into five functional classes: (i) Se metabolism; (ii) energy metabolism; (iii) stress/adhesion; (iv) cell shape and transport; (v) proteins involved in other functions. All the experimental results indicate that L. reuteri Lb2 BM is able to metabolize Se(IV), incorporating it into selenoproteins, through the action of a selenocysteine lyase, thus enhancing organic Se bioavailability. This involves endo‐ergonic reactions balanced by an increase of substrate‐level phosphorylation, chiefly through lactic fermentation. Nevertheless, when L. reuteri was grown on Se a certain degree of stress was observed, and this has to be taken into account for future applicative purposes. The proteomic approach has proven to be a powerful tool for the metabolic characterization of potential Se‐concentrating probiotics.