Browsing by Author "Kamimura, Bruna A."
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- Anti-listerial activity of lactic acid bacteria isolated from artisanal cheeses produced in the State of Minas Gerais, BrazilPublication . Campagnollo, Fernanda B.; Margalho, Larissa P.; Kamimura, Bruna A.; Alvarenga, Verônica O.; Cadavez, Vasco; Gonzales-Barron, Ursula; Sant'Ana, Anderson S.Introduction: Brazilian artisanal cheeses, among them Minas cheeses, are highly appreciated by consumers. Nonetheless, some cheeses have been regularly found to harbour high-risk pathogens, such as Listeria monocytogenes, mainly arising from their elaboration with raw milk and informal production. However, cheese matrices are complex systems whose microbial competing factors (i.e., indigenous lactic acid bacteria (LAB)) and intrinsic properties (acidity, temperature, and water activity) can act as effective hurdles against L. monocytogenes proliferation. Purpose: The aim of this study was to evaluate the capacity of LAB strains isolated from Minas artisanal cheeses as anti-listerial agents. Methods: A total of 891 LAB strains were isolated from 244 Minas artisanal cheese samples (466 using MRS agar (MRSLAB) and 425 using M17 agar (M17LAB)), which were tested qualitatively for anti-listerial activity by the deferred antagonism assay at 30oC (24 h). Two L. monocytogenes strains, serotypes 1/2b and 4b, isolated from cheese and crude milk, respectively, were used. LAB strains with positive anti-listerial activity at 30oC were further tested at 7oC (10 days). Results: MRSLAB strains presented significantly better anti-listerial activity at 30oC (73.0% and 70.8% for serotypes 1/2b and 4b, respectively) compared to M17LAB strains (21.2% and 23.1%, respectively), and there was no significant difference between listeria serotypes (P<0.05). Selected MRSLAB and M17LAB strains were able to keep anti-listerial activity at 7oC, with no significant differences between MRSLAB (96.8% and 97.2% for listeria 1/2b and 4b, respectively) and M17LAB (95.2% and 96.8%, respectively) or between Listeria serotypes (P<0.05). Significance: These results suggested that LAB isolated from Minas cheeses using MRS agar present a better inhibitory effect against L. monocytogenes at different temperatures. These strains can be used as starter cultures in order to inhibit pathogen survival.
- Selection of indigenous lactic acid bacteria presenting anti-listerial activity, and their role in reducing the maturation period and assuring the safety of traditional Brazilian cheesesPublication . Campagnollo, Fernanda B.; Margalho, Larissa P.; Kamimura, Bruna A.; Feliciano, Marcelo D.; Freire, Luisa; Lopes, Letícia S.; Alvarenga, Verônica O.; Cadavez, Vasco; Gonzales-Barron, Ursula; Schaffner, Donald W.; Sant'Ana, Anderson S.Artisanal raw milk cheeses are highly appreciated dairy products in Brazil and ensuring their microbiological safety has been a great need. This study reports the isolation and characterization of lactic acid bacteria (LAB) strains with anti-listerial activity, and their effects on Listeria monocytogenes during refrigerated shelf-life of soft Minas cheese and ripening of semi-hard Minas cheese. LAB strains (n ¼ 891) isolated from Minas artisanal cheeses (n ¼ 244) were assessed for anti-listerial activity by deferred antagonism assay at 37 C and 7 C. The treatments comprised the production of soft or semi-hard Minas cheeses using raw or pasteurized milk, and including the addition of selected LAB only [Lactobacillus brevis 2-392, Lactobacillus plantarum 1-399 and 4 Enterococcus faecalis (1-37, 2-49, 2-388 and 1-400)], L. monocytogenes only, selected LAB co-inoculated with L. monocytogenes, or without any added cultures. At 37 C, 48.1% of LAB isolates showed anti-listerial capacity and 77.5% maintained activity at 7 C. Selected LAB strains presented a bacteriostatic effect on L. monocytogenes in soft cheese. L. monocytogenes was inactivated during the ripening of semi-hard cheeses by the mix of LAB added. Times to attain a 4 log-reduction of L. monocytogenes were 15 and 21 days for semi-hard cheeses produced with raw and pasteurized milk, respectively. LAB with anti-listerial activity isolated from artisanal Minas cheeses can comprise an additional barrier to L. monocytogenes growth during the refrigerated storage of soft cheese and help shorten the ripening period of semi-hard cheeses aged at ambient temperature.