Isolamento de bactérias láticas produtoras de bacteriocinas e avaliação de sua atividade frente a patógenos alimentares em sistema de bioconservação de produto lácteo
Nenhuma Miniatura disponível
Data
2016-07-05
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal de Goiás
Resumo
Due to their antagonistic activity against undesirable microorganisms, lactic acid bacteria
(LAB) are a promising alternative for conservation and improvement of food safety. The aim
of this work was isolate, from fresh Minas cheese, bacteriocin producing LAB with potential
for use in biopreservation systems of dairy products. For this purpose, cheese samples were
evaluated at the beginning and end of their shelf life and the isolation was performed by
surface plating on MRS agar. The antimicrobial activity was verified by antagonism assay
using Listeria monocytogenes ATCC 7644 and Staphylococcus aureus ATCC 25923 as
indicators microorganisms. The selected LAB were submitted to the spot-on-the-lawn test,
Gram stain, catalase and oxidase production and glucose metabolism in Hugh & Leifson
broth. The occurrence of inhibition due to the production of organic acids and bacteriophages
was discarded. The protein nature of antagonistic substances was confirmed by using
proteases. After the well-diffusion assay, four LAB with satisfactory antagonistic activity
against the indicators microorganisms were selected for identification by sequencing of the
16S RNA gene. All bacteria were identified as Lactococcus lactis. Based on antagonism
assay, Lactococcus lactis QMF 11 was selected for use in co-inoculation studies with
pathogens in pasteurized milk, kept at 8°C for 10 days. Lactobacillus sakei ATCC 15521 was
used as negative control for bacteriocin production. After incubation period, monocultures of
Listeria monocytogenes reached 8 log cfu mL-1 and in the presence of Lactobacillus sakei
ATCC its population achieved 7.3 log cfu mL-1. However, when co-inoculated with
Lactococcus lactis QMF 11, Listeria monocytogenes counts were maintained at the initial
inoculum levels, not surpassing 2.3 log cfu mL-1 at the end of analysis. Regarding to
Staphylococcus aureus, in the end of the experiment, cultures counts were 5.4 log cfu mL-1
(monocultures), 5.0 log cfu mL-1 (co-inoculation with Lactobacillus sakei) and 4.7 log cfu
mL-1 (co-inoculation with Lactococcus lactis QMF 11). Despite the lower growth inhibition
in comparison with Listeria monocytogenes, Staphylococcus aureus growth was significantly
affect (p < 0.005) by the presence of Lactococcus lactis QMF 11, indicating that this strain
has potential for use as biopreservative culture in dairy products.
Descrição
Citação
COSTA, A. C. C. C. Isolamento de bactérias láticas produtoras de bacteriocinas e avaliação de sua atividade frente a patógenos alimentares em sistema de bioconservação de produto lácteo. 2016. 58 f. Dissertação (Mestrado em Ciência e Tecnologia de Alimentos) - Universidade Federal de Goiás, Goiânia, 2016.