الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Bacteriocins are ribosomally synthesized antimicrobial compounds that are produced by many different bacterial species including many
members of the lactic acid bacteria .The purpose of this study was isolation
and selection of some lactic acid bacteria (LAB) belonging to the genera
Lactobacillus spp. from raw milk and Ras cheese and study its ability to
produce bacteriocins, with respective biology activity against pathogenic
bacteria. The studies presented in this thesis include:
1- Screening of LAB isolated from raw milk and dry cheese for the
production of bacteriocins. Only 4 strains out of sixteen isolates, belonging
to the species L. fermentum, L. acidophilus, L. acidophilus and L. pentosus,
showed activity towards indicator strains with disk well diffusion and
teterazolum chloride test method. It is the first time that baceriocin activity is
reported in E.coli ATCC 25922 and Bacillus subtilis NCIB3610.
2- Detection and identification of known strains by using different methods
such as biochemical tests, API system and using RAPD PCR for detection
the relationship between four strains.
3- Evaluation of bacteriocins production in liquid media from four strains
such as:
A- Influence of different media on the bacteriocins production:
a maximum bacteriocin activity was shown (3200 AU/ml) in medium
C by L. acidophilus CH1 against Bacillus subtilis NCIB3610, but the
minimum bacteriocin activity obtained by all strains was 0.0 AU/ml in
all media against E.coli ATCC 25922 except MRS mediun.
Summary
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B- Effect of different temperature on bacteriocins production: the
highest activity was obtained with L.acidophillus CH1 (1600AU/ml
against E.coli ATCC 25922 and 2100 AU/ml Bacillus subtilis).
C- Effect of different levels of pH on bacteriocins production
activity: The best pH for bacteriocin activity was pH=6. The highest
activity was obtained with L.acidophillusCH1 (2800AU/ml against
E.coli ATCC 25922 and 3300 AU/ml against Bacillus subtilis).
D- Effect of medium composition on bacteriocin production activity:
the highest bacteriocin activity was 2700AU/ml when the medium
was supplemented with K2HPO4 (1%) using L.acidophillusCH1
against B. subtilis. The lowest activity 0.0 AU/ml was shown in
different concentrations from (2-3%) with other media components.
4- Different parameters of characterization of bacteriocins such as:
A- Effect of different concentrations of NaCl on crude bacteriocins
activity: L. fermentum M1 produced 1500 AU/ml against B. subtilis.
The lowest bacteriocins activity obtained was 0.0 AU/ml for all
strains at 10% NaCl against E.coli and B.subtilis.
B- Effect of different concentrations of amino acids on crude
bacteriocin activity: The best activity was obtained at control
(without addition of amino acids) for Lactobacillus acidophilus CH1
(1600 AU/ml) against B. subtilis. The smallest activity value was 0.0
AU/ml at concentration of 8% amino acids for all tested strains
against B. subtilis.
C- Effect of different vitamins on crude bacteriocins activity: The
best bacteriocins activity was 1400 AU/ml for L. fermentum M1and L.
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acidophillus CH1 against E.coli ATCC 25922 but most tested
strains showed no activity with B12 against E.coli.
D- Effect of different temperatures on the crud bacteriocins activity:
1- L. fermentum M1 showed the highest inhibition percentage was
(76.08%) at 60ºC/30min against E.coli but the smallest activity was
(30.01%) at 30ºC/30min against B.subtilis.
2- The strain L. acidophilus M2 showed the highest growth inhibition
(87.34%) at 60ºC/30min against E.coli and the smallest activity was
11.12% at 90ºC/30min against E.coli.
3- L.acidophilusCH1 with highest activity was 87.08% at 30ºC/30min
against B.subtilis and smallest activity was 18.08% at 90ºC/30min
against B.subtilis.
4- L. pentosus CH2 which showed the highest activity of growth
inhibition 85.98% at 60ºC/30min against B.subtilis but the smallest
activity was at 90ºC/30min against E.coli.
E- Effect of surfactant on crude bacteriocins activity:
1- L. fermentum M1 showed the highest bacteriocins activity, growth
inhibition was 73.56% with Tween 80 against E.coli but the lowest
activity was -30.81% with ETDA against E.coli.
2- L. acidophilus M2 which showed the highest growth inhibition
percentage (78.59) with SDS against B.subtilis but the lowest
activity was -8.37% with ETDA against E.coli.
3- L.acidophilus CH1 showed the highest activity (78.29%) with
Tween 80 against E.coli but showed the lowest activity (-23.70%)
with ETDA against E.coli.
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4- L. pentosus CH2 showed the higest activity ( 80.59%) with CTAB
against E.coli but the smallest activity was -85.11% with Tween80
against E.coli.
F- Effect of some mineral salts on crude bacteriocins activity:
1- L. fermentum M1 showed the highest bacteriocins activity (87.2%)
with FeSO4 against B.subtilis but the smallest activity was -64.5%
with AgNO3 and CuSO4 against E.coli.
2- L. acidophilus M2 which showed the highest growth inhibition
percentage (95.57) with FeSO4 against B.subtilis but the smallest
activity was -62.96% with ZnSO4 against E.coli.
3- L.acidophilusCH1 showed the highest activity of growth inhibition
(97.92%) with FeSO4 against E.coli, but showed the smallest
activity (-81.03%) with ZnSO4 against E.coli.
4- Strain L. pentosus CH2 showed the highest activity of growth
inhibition (97.17%) with FeSO4 against B.subtilis but the smallest
activity was -82.96% with MnCl2 against E.coli.
G- Effect of some solvents on crude bacteriocins activity:
1- L. fermentum M1 showed the highest bacteriocins activity of
growth inhibition percentage (93.85%) with Isoamylchloride
against B.subtilis but the smallest activity was 0.0% against E.coli.
2- L. acidophilus M2, showed the highest growth inhibition
percentage (87.69) with ethanol against B.subtilis but the smallest
activity was -33.7% with Isoamylchloride against B.subtilis.
3- L.acidophilusCH1, showed the highest activity of growth
inhibition (88.93%) with Isopropanol against B.subtilis but showed
the smallest activity (-48.15%) with chloroform against E.coli.