Goat Milk and Cheeses May be a Good Source for Antilisterial Bacteriocin-Producing Lactic Acid Bacteria

ABSTRACT

The aim of this study was to isolate new bacteriocin-producing lactic acid bacteria (LAB) from goat milk and cheeses produced in Sao Paulo State, Brazil, with activity against Listeria monocytogenes. Samples of goat milk obtained from a farm (Sitio Rekantinho, Ibiúna, SP, Brazil) and goat cheeses obtained from a local supermarket (Butanta, Sao Paulo, SP, Brazil) were screened for presence of bacteriocin-producing LAB. Based on preliminary inhibition tests performed using the three levels method described by Todorov (2008), more than 30% of the LAB colonies isolated from these products were potential bacteriocin producers. These colonies were isolated and confirmed for bacteriocin production using L. monocytogenes ScottA, L. monocytogenes ATCC 7644 and L. innocua USP FCF 01 as indicators of inhibitory activity. A total of 14 isolates were selected and identified based on API 50 CHL and 16S rRNA sequencing. The bacteriocins of all 14 isolates inhibited the growth of a large number of L. monocytogenes strains from different serological groups. The highest bacteriocins production was recorded during the beginning of stationary growth phase and remained stable for at least 24 h at 30°C. Treatment of the cell-free supernatants with proteolytic enzymes inhibited the antimicrobial activity of the bacteriocins. No significant changes in bacteriocin activity of all 14 isolates were recorded when they were exposed to pH from 2.0 to 12.0, and to temperatures from 25°C to 100°C for 2h. These LAB strains present an interesting potential of application as biotechnological tools for improvement of the microbiological safety of goat cheeses.

Keywords:

• bacteriocin
• cheese
• milk
• Listeria monocytogenes