Identificação e caracterização do potencial probiótico de bactérias isoladas do leite e queijo caprino

Abstract

The search for new bacteria with functional properties has been the focus of intense research in recent decades. Several species of Lactobacillus gender are known as probiotic and are added in foods. To be selected as a probiotic bacteria, it need to present certain characteristics, as capacity to survive the gastrointestinal conditions and be free of pathogenic. The aim of this study was to isolate, identify and select strains of Lactobacillus from goat milk and cheese, and evaluate its potential probiotic and its safety through the identification of related genes with beneficial characteristics and risks for human consumption, checking its in vitro expression. Were identified twenty-three different strains of Lactobacillus plantarum and added to study other four strains of L. plantarum and three Lactobacillus mucosae. The thirty strains were evaluated for the presence of genes related to probiotic properties as bsh gene, coding for the enzyme bile salt hydrolase, the msa, related to capacity of adhesion to intestinal epithelium induced by mannose, three other genes map, mub and ef-tu associated the mucus adhesion properties. The bsh and msa gene had their expression evaluated in vitro, by means of biochemical tests deconjugation of bile salts and addition of yeast, respectively. The results show that 80% of the strains were able to survive in the presence of bile salts and 76% were able to deconjugate at least one of the four salts tested. As for the adhesion capacity, four strains show a positive result, and three of them confirmed interactinon via mannose. Still evaluating adhesion properties, only two strains have a high hydrophobicity value in the cell suface, property that has been linked indirectly to the ability to adhere to the intestinal mucosa, and 90% from these strains have a genetic profile favorable for binding to the intestinal mucosa, with three of the four genes adherence evaluated. The safety of the microorganisms was also evaluated for the presence and expression of the thirteen genes related to virulence factors, including resistance to antibiotics and production of biogenic amines. The expression of genes associated with the production of gelatinase (gelE), and tyrosine amines (TDC) and histamine (hdc1 and hdc2) and resistance to vancomycin (vanA and vanB) was investigated by means of biochemical tests. Although some strains amplify the gelE gene it did not show in vitro expression. Was verified in vitro resistance to vancomycin, very common among lactobacilli, also observed in strains that did not amplify the genes vanA and vanB. With respect to production of biogenic amines, only the tdc gene for tyrosine was detected in strains, one of the genes with the greatest percentage of amplification. However, only one strain that presented the gene had its expression confirmed in vitro test using descarboxilação medium, while some strains that do not amplify the gene had positive results in vitro. Fourteen isolated did not amplified genes related to virulence. Of these, only the Lactobacillus plantarum Q24 strain showed no expression in vitro related to virulence factor, in addition to amplify three of the genes related to adherence to mucus, and have survived and disconjugate two of bile salts evaluated, showing be the most promising to pursue studies potential of probiotic research.