Characterization of inhibitory supernatants produced by bacteria isolated from goat milk

Liliane Andrade Da Silva,Octávio Luiz Franco,Kléber De Sousa Oliveira,Annie Evelyn Souto Raposo,Evandro Leite Souza,Haíssa Roberta Cardarelli,José Honório Pereira Lopes Neto

doi:10.33448/rsd-v11i2.25280

Abstract

Several compounds can be produced by lactic acid bacteria (LAB) isolated from milk such as bacteriocins, small cationic and thermostable peptides, that possess antimicrobial activity. The technological application of these antimicrobial compounds became important for the industry mainly because of chemical preservatives. This study aimed to isolate LAB with anti-Listeria monocytogenes activity from raw goat milk and to characterize their inhibitory cell-free supernatants (CFS). It was performed Isolation of LAB from raw goat milk, inhibitory activity of the CFS, characterization of CFS inhibitory activity under different conditions, mode of action of the active CFS, adsorption of the anti-Listeria substances present in the CFS of LS2 to L. monocytogenes, molecular identification of LAB isolates with anti-Listeria activity. Three isolated strains produced CFS with active inhibitory substances of proteinaceous nature, identified by 16S rDNA as Weissella cibaria (LS1) and Lactococcus lactis (LS2 and LS3). The CFS of LS2 showed the highest anti-Listeria activity (1600 arbitrary units/mL) after 2 h at pH 6.0 and was bacteriostatic and active at low pH at temperatures of 4 °C to 80 °C. The results suggest that the LS2 strain is a biopreservative culture with potential for applications to control L. monocytogenes in foods.

Highlights

Goat milk is a complete food, composed of proteins, essential fatty acids, minerals, and vitamins (Queiroga et al, 2016)
The raw goat milk microbiota is considered a good source of novel bacteriocinogenic strains that can be exploited as an alternative for use as biopreservatives in foods (Perin and Nero 2014)
3.1 Lactic acid bacteria (LAB) from raw goat milk and cell-free supernatants (CFS) activity A total of 19 Gram-positive and catalase-negative cultures were isolated from raw goat milk; CFS obtained from these isolates revealed no activity against the Gram-negative bacteria tested (Salmonella spp. and Escherichia coli ATCC 29214)

Summary

Introduction

Goat milk is a complete food, composed of proteins, essential fatty acids, minerals, and vitamins (Queiroga et al, 2016). Lactic acid bacteria (LAB) naturally found in goat milk can produce several compounds with activity against other bacteria, including bacteriocins (Furtado et al, 2015). Bacteriocins are generally small cationic and thermostable peptides that possess antimicrobial activity. These molecules show variations regarding their molecular masses, biochemical properties, spectrum of antibacterial activity, and mechanism of action (Biscola et al, 2013; Furtado et al, 2015; Umu et al, 2016). Bacteriocins produced by LAB can inhibit growth and survival of pathogenic and spoilage microorganisms in foods. Assayed in food-based systems, bacteriocins from LAB inhibit Bacillus cereus, Staphylococcus aureus, Clostridium tyrobutyricum, Pseudomonas aeruginosa and L. monocytogenes (Bizani et al, 2008; Furtado et al, 2015; Malheiros; Cuccovia and Franco, 2016; Barman; Ghosh and Mandal, 2018; Kaktcham et al, 2019)

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