Goat breeding in Sardinia constitutes an important source of income for agricultural and pastoral activities. Goat milk indeed is intended for direct consumption and cheese processing. In this study, goat milk was used as source of bacteriocin-producing strains. Many lactic acid bacteria (LAB) produce bacteriocins with rather broad spectra of inhibition and could offer potential applications in food preservation. A group of 170 LAB were isolated from Sardinian goat milk and tested for the production of bacteriocin/s by agar spot-test and well-diffusion-method against several food-borne pathogenic microorganisms. Four strains (SD1, SD2, SD3 and SD4) were selected for their effective inhibition on Listeria monocytogenes. The selected isolates were classified as member of Enterococcus genus according to their biochemical and physiological characteristics. Based on 16s rDNA sequencing, the four isolates was then classified as Enterococcus faecium. In MRS broth at 37oC, bacteriocins SD1 and SD2 were produced at much higher levels (25600 AU/mL) compared to bacteriocin SD3 (1600 AU/mL) and bacteriocin SD4 (800 AU/ml). Their peptides were inactivated by proteolytic enzymes, but not when treated with a-amylase, catalase and lypase. The four bacteriocins remained stable at pH from 2.0 to 12.0 and after exposure at 100oC for 120 min and in presence of surfactants and salts (such as N-Laourylsarcosine, NaCl, SDS, Triton X-100, Tween 20, Tween 80 and urea). Their molecular size was determined by tricine-SDS-PAGE to be approximately 8 kDa. In conclusion, the bacteriocins SD1, SD2, SD3 and SD4 activity was determined against several LAB, L. monocytogenes from different serological groups and Gram-negative bacteria. Since the strains exhibited a strong antimicrobial activity against 21 L. monocytogenes strains and 6 Salmonella spp. isolates, they should be considered as a potential bio-preservatives starter cultures for fermented food productions. A future study on their technological properties and safety needs to be performed.

Sardinian goat milk as a source of bacteriocinogenic strains

FAVARO, LORENZO;BASAGLIA, MARINA;CASELLA, SERGIO;
2010

Abstract

Goat breeding in Sardinia constitutes an important source of income for agricultural and pastoral activities. Goat milk indeed is intended for direct consumption and cheese processing. In this study, goat milk was used as source of bacteriocin-producing strains. Many lactic acid bacteria (LAB) produce bacteriocins with rather broad spectra of inhibition and could offer potential applications in food preservation. A group of 170 LAB were isolated from Sardinian goat milk and tested for the production of bacteriocin/s by agar spot-test and well-diffusion-method against several food-borne pathogenic microorganisms. Four strains (SD1, SD2, SD3 and SD4) were selected for their effective inhibition on Listeria monocytogenes. The selected isolates were classified as member of Enterococcus genus according to their biochemical and physiological characteristics. Based on 16s rDNA sequencing, the four isolates was then classified as Enterococcus faecium. In MRS broth at 37oC, bacteriocins SD1 and SD2 were produced at much higher levels (25600 AU/mL) compared to bacteriocin SD3 (1600 AU/mL) and bacteriocin SD4 (800 AU/ml). Their peptides were inactivated by proteolytic enzymes, but not when treated with a-amylase, catalase and lypase. The four bacteriocins remained stable at pH from 2.0 to 12.0 and after exposure at 100oC for 120 min and in presence of surfactants and salts (such as N-Laourylsarcosine, NaCl, SDS, Triton X-100, Tween 20, Tween 80 and urea). Their molecular size was determined by tricine-SDS-PAGE to be approximately 8 kDa. In conclusion, the bacteriocins SD1, SD2, SD3 and SD4 activity was determined against several LAB, L. monocytogenes from different serological groups and Gram-negative bacteria. Since the strains exhibited a strong antimicrobial activity against 21 L. monocytogenes strains and 6 Salmonella spp. isolates, they should be considered as a potential bio-preservatives starter cultures for fermented food productions. A future study on their technological properties and safety needs to be performed.
2010
Proceedings of Food Micro 2010
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/2479560
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