Studies on metabolic, antimicrobial and plasmid-DNA profiles of some lactic acid bacteria isolated from kefir

in STUDIES ON METABOLIC, ANTIMICROBIAL AND PLASMID-DNA PROFDLIES OF SOME LACTIC ACID BACTERIA ISOLATED FROM KEFBR (M. Sc. Thesis) Zehra Nur MUMCU GAZI UNIVERSITY INSTITUTE OF SCIENCE AND TECHNOLOGY December 1997 ABSTRACT In this research, a total of 42 lactic acid bacteria (LAB) were isolated. The isolated bacteria were 21 isolates of Lactobacillus spp. and 21 isolates were Streptococcus spp. Identification results of the bacteria were; 1 species of Lactobacillus acidophilus, 2 species of L. helveticus, 4 species of L. casei, 3 species of L. bulgaricus, 6 species of L. lactis, 3 species of L. plantarum, 2 species of L. brevis, 4 species of S. lactis, 3 species of S. thermophilus, 3 species of S. durans and 1 1 species of S. cremoris. Amount of lactic acid, hydrogen peroxide, hydrogen sulfide, acetaldehyde and proteolytic activities of Lactobacillus and Streptococcus species was estimated. Amount of diacetyl produced by Streptococcus species was also determined. Inhibitory effect of Lactobacillus and Streptococcus strains on Escherichia coli, coag.(+) Staphylococcus aureus, mutant coag.(-) Staphylococcus aureus, Bacillus subtilis and Pseudomonas aeroginosa was tested. Also, bacteriosin produced by the strains and inhibitory activities of these material were tested on tested bacteria.Amount of PHB produced by the bacteria was estimated. Amount of PHB produced by Lactobacillus and Streptococcus species according to dry cell wt. was 0,52-25,55 and 0,61-13,69%, respectively. Five Lactobacillus spp. and 6 Streptococcus spp. with high inhibition activities were used for shading their plasmid DNA profiles. L. acidophilus ZİL contains 3 plasmids (13,42, 7,02 and 3,58 kb), L. casei Z3L contains 3 plasmids (25,42, 21,34 and 1 1,47 kb), L. brevis Z13L contains 5 plasmids (34,23, 25,42, 20,42, 9,13 and 2,59 kb), S. lactis Z1S contains 4 plasmids (23,70, 20,61, 17,15 and 8,67 kb), S. laclis Z3S contains 2 plasmids (23,49, 16,41 kb), S. durans Z15S contains 5 plasmids (21,89, 18,39, 17,29, 8,89 and 4,42 kb). L. casei 7AL, L. bulgaricus Z8L, S. thermophilus Z5S, S. cremoris Z6S and Z10S strains did not have any plasmid. Science Code : 401.02.00 Key Words : Kefir, Lactobacillus, Streptococcus, metabolic and antimicrobial activities, plasmid, bioplastic (Poly-P-hydroxybutyrate) Page Number : 129 Adviser : Assoc. Prof. Dr. Yavuz BEY ATLI