Bacteriocin producing lactic acid bacteria isolated from Mongolian traditional fermented milk
- VernacularTitle: Монгол айрагнаас ялган авсан бактериоцин нийлэгжүүлэгч сүүн хүчлийн бактерийн судалгаа
- Author:
Batjargal B
1
;
Sukhdolgor J
;
Ochirkhuyag B
Author Information
1. Department of Biochemistry and Bioorganic chemistry, School of Biology and Biotechnology, NUM
- Publication Type:Journal Article
- Keywords:
Airag;
Lactic acid bacteria;
bacteriocin;
Enterococcus durans
- From:
Health Laboratory
2014;3(1):10-16
- CountryMongolia
- Language:Mongolian
-
Abstract:
Airag is a Mongolian traditional fermented equine milkbeverage, also known as koumiss in some parts of the world, fermented by a co-culture of yeasts and lactic acid bacteria. Little information is available on the bacterial communities in Mongolian traditional airag made from raw mare’s milk. Lactobacillus spp., Lactococcus spp., Enterococcus spp., and Leuconostoc species were isolated from airag. Strains of enterococci, including E. faecium and E. faecalis, are known to produce bacteriocins. These are called enterocins and they generally belong to class II bacteriocins. However, detailed studies of bacteriocins from Enterococcus durans are rare. The aim of this study was to isolate and identify bacteriocin-producing lactic acid bacteria (LAB) issued from Mongolian airag (traditional fermented mare’s milk), and to purify and characterize bacteriocins produced by theseLAB.Identification of the bacteria (Enterococcus durans) wascarried out on the basis of its morphological, biochemical characteristics andcarbohydrate fermentation profile by API50CH kit and 16S rDNA analyses.The pH-neutral cell-free supernatant of this bacterium inhibited the growth of several Lactobacillus spp. and food-borne pathogens including Escherichia coli,Staphylococcus aureus and Listeria innocua. The antimicrobial agent (enterocin A5-11) was heat stable and was not sensitive to acid and alkaline conditions (pH 2–10), but was sensitive to several proteolytic enzymes. Its inhibitoryactivity was completely eliminated after treatment with proteinase K anda-chymotrypsin. Three-step purification procedure withhigh recovery yields was developed to separate two bacteriocins. The appliedprocedure allowed the recovery of 16% and 64% of enterocinsA5-11A andA5-11B, respectively, present in the culture supernatant with purity higher than99%. SDS-PAGE analyses revealed that enterocin A5-11 has a molecular massof 5000 Da and mass spectrometry analyses demonstrates molecular masses of5206 and 5218 Da for fractions A and B, respectively. Amino acid analyses ofboth enterocins indicated significant quantitative difference in their contents in threonine, alanine, isoleucine and leucine. Their N-termini were blocked hamperingstraightforward Edman degradation.The minimuminhibitory concentration of bacteriocinsA5-11A andA5-11B was8.2 µM l-1and 9,2 µM l-1, respectivelyBacteriocins A5-11A and B from Ent. durans belong to the classII of bacteriocins
