Growth intensity and antibacterial properties of Enterococcus faecium and Enterococcus durans strains isolated from traditional Carpathian brynza

Abstract

The article presents the results of the study the ability of four not studied strains of enterococci (E. durans, SB6, E. faecium SB12, E. durans SB18, E. durans SB20), which were isolated from the Carpathian brynza, to reduce the acidity of medium of cultivation, the rate of biomass accumulation and the ability to exhibit antagonistic properties to the opportunistic microflora. Lactic acid and minor compounds are producing in a result of lactose fermentation, which form the specific taste and aroma properties of the product. The activity of acid formation has crucial because it directly connected with the coagulation of proteins and the prevention of the growing of extraneous microflora. Therefore, the rate of acidity increasing of the medium is one of the most important characteristics in selection of strains of lactic acid bacteria for the manufacture of dairy products. High growth rate, resistance to the contamination of extraneous microflora and preservation of their properties in the finished product are the technological properties of the strains. The inhibition of the growth of pathogenic cultures of microorganisms is the main probiotic functions of beneficial bacteria namely antagonistic activity. It was found, that the strain E. durans SB20 manifested the highest ability to increase the acidity of the medium under the cultivation for 24 hours at 37 °C as it reduced the pH on 30.3 %, and the strain E. durans SB18 increased the acidity on 29.9 %. Under 48 hours strains E. durans SB20 and SB18 increased the acidity on 31.1 and 30.5 % (P< 0.001) respectively compared with the control. The growth rate of stains E. durans SB20 and E. durans SB18 were in 18,0 and 17,6 times higher than in control under the cultivation for 24 hours at 37 °C, the optical density were in 18.3 and 18.2 times higher respectively than in the control sample under the cultivation for 48 hours at the same temperature. Furthermore, strains of enterococci showed antagonistic properties against conditionally pathogenic cultures of microorganisms on 24 and 48 hour of cultivation. In addition, it was found that with an increasing temperature of the antagonistic activity of the strains cultivation increased. Obviously, it was connected that more biologically active substances and microbial secondary metabolites are formed under the longer cultivation and higher temperatures. In particular on 48 hours at 37 °C almost of all the tested strains showed moderate antagonistic activity against E. coli, S. enteritidis, E. aerogenes, P. mirabilis and P. aeruginosa. However, all four strains didn`t have antagonistic activity against the test-strain S. aureus.