Avaliação de propriedades probióticas e tecnológicas in vitro de bactérias ácido láticas isoladas de Queijos Coloniais artesanais comercializados em Pelotas, RS

Abstract

Lactic acid bacteria are defined as a group of gram-positive, catalase-negative, unsporulated, aerobic, microaerophilic or facultative anaerobic rods and rods and produce lactic acid as the main end product during carbohydrate fermentation. This group of bacteria is generally recognized as safe and plays an important role in fermentation and food preservation processes, either as native microbiota and starter or adjunct cultures added under appropriate conditions, and is the major representative of probiotics in food, providing several beneficial effects to the health of the host. Due to the benefits already reported in the literature, the search for new strains with these characteristics has been relevant. In the far south of Brazil, a cheese made from artisanal raw milk, known as artisanal colonial cheese, is a source of wild lactic acid bacteria. However, the objective of this work was to evaluate the probiotic and technological potential in vitro of lactic acid bacteria isolated from artisanal colonial cheese marketed in Pelotas, RS. It were isolated 105 strains, 73 were characterized as gram positive and catalase negative and evaluated for phenotypic aspects of virulence. All strains were gelatinase and DNase negative. Regarding hemolytic activity, seven strains were detected as α and two as β-hemolytic, resulting in 64 LAB strains for antimicrobial susceptibility evaluation. These isolates were susceptible to chloramphenicol and tetracycline antibiotics. For the other antimicrobials, they were resistant to ciprofloxacin (93.5%, 58/64), oxacillin 98.4% (63/64), Penicillin G 51.6% (41/64) and vancomycin (85.9%, 54/64). Antagonist activity of 63 strains was verified by the spot on the lawn method against Staphylococcus aureus 25923, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium and Salmonella enteretidis, Lactobacillus acidophilus ATCC 4356, Lactobacillus brevis ATCC 367 Lactobacillus plantarum ATCC 8014 and Lactobacillus fermentum ATCC 9338. Four isolates were discarded for not showing activity against the pathogens, while the other 59 isolates presented for at least two strains. About 22% of the LAB isolates (13/59) presented antagonism in relation to at least one reference LAB, being L. acidophilus and L. brevis the ones with the highest inhibition of 92.3% (12/13) and 77% (10/13). The 59 LABs were verified by bacteriocin production through the well diffusion technique. Four LAB (Q1LAB10, Q2LAB2, Q4LAB1 and Q4LAB5) were able to produce bacteriocins against L. monocytogenes, extracellular proteinases and from these Q2LAB2 and Q4LAB1 were able to decrease the milk pH from 6.5 to 5.3 within 6h. However, strains Q2LAB2 and Q4LAB1 have been potentially identified as starter anti-Listeria cultures for use in the biopreservation of dairy products.