Potencial probiótico, tecnológico e aspectos de segurança de bactérias ácidoláticas isoladas de kefir e de kombucha

Abstract

Recent scientific researches have revealed a growing and notorious interest in the consumption of products that are beneficial to health. From this perspective, probiotics have gained great visibility, as they are live microorganisms that, when ingested in enough numbers, bring benefits to the consumer's health. Beverages such as kefir and kombucha have a variety of microorganisms with probiotic potential. The consumption of these can promote human health, and consequently, have been the object of study. Thus, the aim of this study was to isolate, identify and characterize lactic acid bacteria (LAB) from kefir and kombucha with probiotic potential and to evaluate in vitro safety aspects. The isolation and characterization of microorganisms were carried out using Gram stain, presence of catalase and morphology tests. Afterwards, safety aspects were evaluated through the activity of gelatinase, DNAse, hemolysin enzymes and susceptibility to clinically used antimicrobials. Furthermore, the cytotoxicity assay was performed using the MTT method using VERO cell lines. The technological properties were verified through the antimicrobial activity against pathogenic microorganisms by the well diffusion method, determination of the antioxidant capacity by the 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical capture method and reaction to thiobarbituric acid (TBARS). To analyze the probiotic potential, analyzes of tolerance to conditions of the simulated gastrointestinal tract, tolerance to different acid categories and tolerance to bile salts were analyzed. According to the results obtained, of the eight (n=8) isolates formed belonging to the BAL group (A1, A2, A3, A4, A5, A6, A7 and KAC), five (n=5) showed cocci morphology (A1, A3, A4, A5, A6) and three (n=3) of bacilli (A2, A7, KAC). All isolates showed negative results for gelatinase, DNAse and hemolysin tests. For the antimicrobial susceptibility test, it was found that all isolates showed susceptibility to vancomycin, penicillin, meropenem and chloramphenicol. Regarding the evaluation of technological properties, five (n=5) isolates (A1, A2, A3, A7 and KAC) showed antimicrobial characteristics against all the microorganisms used. Five (n=5) isolates (A1, A4, A6, A7, KAC) showed homofermentative metabolism. With the DPPH and TBARS method, it was observed that all isolates showed antioxidant capacity. For the self-aggregation, coaggregation and hydrophobicity test, isolates A2 and KAC presented the highest percentages of these parameters. Thus, two (n=2) isolates (A2 and KAC) were selected to perform the tolerance tests to different concentrations of acids, bile salts and simulated gastrointestinal tract. Both isolates showed tolerance to gastrointestinal transit in a simulated way. For the cytotoxicity assay, the isolate A2 was used and after one hour of exposure, the bacterial suspension showed no cytotoxicity in the VERO cell lines. These results are promising, as the microorganisms under study showed desirable characteristics for future applications in food matrices.