Purification and characterization of two bacteriocins produced by lactic acid bacteria isolated from Mongolian airag

Abstract

Aims: 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 these LAB. Methods and Results: Identification of the bacteria (Enterococcus durans) was carried out on the basis of its morphological, biochemical characteristics and carbohydrate fermentation profile and 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 inhibitory activity was completely eliminated after treatment with proteinase K and a-chymotrypsin. The activity was however not completely inactivated by other proteases including trypsin and pepsin. Three-step purification procedure with high recovery yields was developed to separate two bacteriocins. The applied procedure allowed the recovery of 16% and 64% of enterocins A5-11A and A5-11B, respectively, present in the culture supernatant with purity higher than 99%. SDS-PAGE analyses revealed that enterocin A5-11 has a molecular mass of 5000 Da and mass spectrometry analyses demonstrates molecular masses of 5206 and 5218 Da for fractions A and B, respectively. Amino acid analyses of both enterocins indicated significant quantitative difference in their contents in threonine, alanine, isoleucine and leucine. Their N-termini were blocked hampering straightforward Edman degradation. Conclusions: Bacteriocins A5-11A and B from Ent. durans belong to the class II of bacteriocins. Significance and Impact of the Study: Judging from molecular masses, amino acid composition and spectrum of activities, bacteriocins A5-11A and B from Ent. durans show high degree of similarity with enterocins L50A and L50B isolated from Enterococcus faecium (Cintas et al. 1998(Cintas et al. , 2000 and with enterocin I produced by Ent. faecium 6T1a, a strain originally isolated from a Spanish-style green olive fermentation (Floriano et al. 1998).

Screening of lactic acid bacteria from vacuum packaged beef for antimicrobial activity

“…De Martinis and Freitas (9), evaluating vacuum packaged beef, found only three strains capable of inhibiting Lactobacillus species and Listeria monocytogenes. On the other hand, a higher number of LAB producing inhibitory substances has been found in dairy products and fermented grains (3,12,15,17,18).…”

Investigation of the Properties of Endemic LAB Strains of Genus Enterococcus Isolated From Samples of Cow Matsoon

“…Colonies of isolated LAB differed by color, shape and size when inoculated in agar media (MRS and/or hydrolyzed milk). Strains study at separate and joint cultivation in milk (3,2 %) showed a change in the total acidity of from 80 to 120 ° T to, within 12 days of storage in the refrigerator +4 0 C. LAB strains were mainly presented by coccoid cells (about 86 %),which may be due to the climatic conditions of the southern region.Isolated colonies of strains of LAB grows in MRS and fermented milk 7-8 hours at a temperature of 30 and 37 0 C. The main probiotic characteristics of selected LAB strains were investigated according to the methods described [3,6]. The results of which are shown in Table 1.…”

“…Culture broth was collected after 24 hrs and centrifuged at 6,000 rpm during 20 min. Cell free culture broth of LAB strains was concentrated 5 times and purified by gel filtration method (Sephadex G25) [3]. Determination of antimicrobial activity.…”

Effect of Enterococcus Durans Bacteriocin on Bacterial Wilt Agent

“…Bacteriocin from Enterococcus durans A5-11 strain was purified by cation-exchange chromatography, reversed phase chromatography and HPLC-chromatography with CHT-column according to Batdorj et al [1]. Bacteriocin solutions of different concentrations (0.10-0.03 mg/ml) were stored at +4 °Ñ and -20 °Ñ, and were adjusted to pH 6.8-7.0 before use for test of antagonistic activity.…”