Screening de bactérias ácido lácticas isoladas de leite e derivados com potencial probiótico

Abstract

Lactic acid bacteria (BAL) are the main representatives of probiotics in foods, providing beneficial effects to host health. Due to the effects already reported in the literature, the search for new lineages with these characteristics has been relevant. Thus, the objective of this study was to isolate, identify and characterize BAL present in dairy foods with probiotic potential, as well as to analyze the antimicrobial effect, the antioxidant capacity and the presence of virulence and resistance factors. To that end, 40 microorganisms from different dairy products (yakult, San Bios, fresh cow's milk, Ricotta, Frescal cheese and Kefir) were selected, and 17 microorganisms were randomly chosen for future analyzes, such as: evaluation of the probiotic properties by pH, bile salts and upper gastrointestinal tolerance tests; determination of the antioxidant properties by the methods of capture of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) and reaction with thiobarbituric acid (TBARS); antimicrobial activity against pathogenic microorganisms by well diffusion and disk diffusion methods; susceptibility to antimicrobials; safety aspects by several methods and detection of genes with potential virulence factor related to adhesion, aggregation and vancomycin resistance, as well as the molecular identification of 16S rDNA by the Sanger method. By means of the obtained results it was observed that all the microorganisms presented some related probiotic characteristic; all presented antioxidant potential by the DPPH method, but by the TBARS method only three microorganisms showed inhibition of lipid peroxidation. Antimicrobial analysis by well diffusion showed that the microorganisms R1, F3 and F4 showed inhibition against Escherichia coli; R1 and R9 against Listeria monocytogenes and K1, K2, R1, R5, and R9 presented antimicrobial action against Staphylococcus aureus. The antimicrobial activity by disk diffusion showed that the microorganisms Y1, Y2, SB4, SB6, R1, R5, R9, L1, L2, L4, K1 and K2 showed inhibition against E. coli; SB4, SB6, F1, F2 and L4 against Salmonella Enteretidis; against L. monocytogenes SB6 and L4 presented inhibitory action; and in relation to S. aureus, antimicrobial activity was observed when the L4 and L5 microorganisms were analyzed. The microorganisms were classified as homofermentative, gelatinase, lipase and DNAse negative; α-hemolytic, non-biofilm forming, and do not show virulence genes such as agg, wing and resistance genes such as vanA. Thus, it was concluded that the microorganisms R9 (Lactococcus lactis subsp. Lactis) and L1 (Leuconostoc citreum) have been shown to be promising microorganisms with potential for use as probiotics, as well as satisfactory antimicrobial and antioxidant properties. This result becomes of paramount importance, considering the possible use of these in future food production.