Abstract
Autochthonous microbiota from artisanal cheeses is predominantly composed of lactic acid bacteria (LAB), which are able to produce antimicrobial compounds, such as bacteriocins, suggesting their application in food biopreservation. Knowledge about LAB growth and bacteriocin production during food production and conservation is essential to determine their use. In this way, the study aimed at isolating bacteriocinogenic LAB from twenty-one artisanal cheeses from the western region of Parana state, Brazil, determining the best conditions for growth and bacteriocin production (25°C, 30°C, and 37°C/24h); bacteriocin stability under different ranges of pH (2, 4, 6, 8, and 10 for 2h) and temperature (60oC/2h; 80oC/2h; 121oC/15min). Their activity against different target microorganisms was also evaluated. A total of 34 LAB strains presented characteristics compatible with bacteriocin production. Most of them presented better results for bacteriocin production when cultured at 25ºC and 30ºC. Bacteriocins remained active against L. monocytogenes when exposed from pH 4 to 8 and a wide temperature range; some bacteriocins were even resistant to sterilization temperatures. Bacteriocins produced were able to inhibit spoilage and pathogenic microorganisms, such as L. monocytogenes, B. cereus, and P. fluorescens. These results indicated that isolated bacteriocinogenic LAB present potential to be used as food biopreservatives.
Highlights
Artisanal cheeses are produced from raw milk and, as a result, most of the autochthonous microbiota is composed of lactic acid bacteria (LAB)
From the 264 BAL strains with antagonist activity against L. monocytogenes, 34 LAB strains (12.9%) obtained from six cheeses were confirmed as bacteriocin producers
Eighteen LAB strains showed greater bacteriocin production when incubated at 25°C, while at 30°C greater production was demonstrated by 20 strains, and at 37°C, only four strains showed improved bacteriocin activity (Table 1)
Summary
Artisanal cheeses are produced from raw milk and, as a result, most of the autochthonous microbiota is composed of lactic acid bacteria (LAB). Bacteriocins are protein substances with inhibitory activity against closely related microorganisms (Reis et al, 2012). Due to their antimicrobial potential, bacteriocins are valuable tools for food safety, especially when it comes to cheeses produced with raw milk. Besides that, their use as biopreservatives can help to reduce the need for chemical additives and rigorous thermal treatments used in food preservation (Favaro et al., 2015) LAB have been recognized as valuable food biopreservatives due to their ability to synthetize antimicrobial substances, such as organic acids, hydrogen peroxide, and bacteriocins, which are able to inhibit spoilage microorganisms and foodborne pathogens (Favaro et al, 2015; Reis et al, 2012; Zacharof and Lovitt, 2012; Castellano et al, 2008; Nero et al, 2008; Deegan et al, 2006).
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