Influence of Various Factors on the Lactococcus Lactis Cells

Abstract

Abstract. Bacteriocin-producing strains of Lactococcus lactis subsp. lactis of different origin were used in our experiments. UV-Irradiation of cells of bacteriocin-synthesizing lactoococci of different origin in a dose of 7.6-7600 erg/mm 2 was followed by their selective growth in an MRS medium, and their selection after UV-ray treatment. Some strains of lactococci had double UV treatment. The novel most active bacteriocin-producing strains were restored after lyophilization and storage. An exposure of 10 minutes should be considered an effective dose of treatment for wide strain 229. As a result, No.12 with an antibiotic activity of 3850 IU / mL was selected, which is 54 % higher than the initial one. The study of the physiological and biochemical properties of the variants, selected after UV-ray treatment, showed that they somewhat changed the rate of their growth and the accumulation of bacteriocin. The relative activity in the production of bacteriocin was calculated as the ratio of activity values and the number of produced cells. The inactivated homologous strain biomass and amino acids were applied as the factors of resuscitation. The control culture liquid was without supplements. VBNC cells of opportunistic strains formed within the first days of incubation. After 1 year of incubation, the VBNC values of Klebsiella pneumoniae 1954, Alcaligenes faecalis 415, Enterobacter aerogenes 418, Proteus vulgaris HX19222, Salmonella typhimurium were statistically equal (97.1-99.9%). After 1 day of stress, the strains of L. lactis did not form colonies up to 60-80%, after 5 days up to 82.1-99.6%, and after 1 year -99.9%. Unwashed from the culture fluid, the inoculated cells proliferated and passed to the VBNC faster. With that inoculation, the nisin productive activity of cells was lower 10-78 times, depending on the strain of L. lactis. The study of resuscitation factors has shown that the supplement of homologous inactivated biomass of L. lactis (0.1%, 0.5%, 1%) was effective with 1% (a magnification of 2.65 at p<0.05) and 0.5% (magnification of 3.75 at p<0.05) only for the MSU strain. Strain F-116 was marked by a 4-fold increase in the ability for cultivation after the addition of 7 aminoacids: (glutamine, methionine, leucine, isoleucine, histidine, arginine, valine). After 1 year, the quantitative level of VBNC cells, which formed in the first days of incubation, was the same for opportunistic and probiotic cultures (97.1%-99.9%). All studied resuscitation factors were individually effective for bacterial strains.