الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
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SUM MAR Y
Most members of the genus streptomyces produced several
voluable biologically active substances such as : enzymes,
vitamins, pigments, growth regulators. toxins and antibiotics.
Antibiotics are very important for human life. plant, animals,
poultry 6S therapeutic agents against different pathogens.
Therefore, this study was carried out to search for
streptomyces isolates from the Egyptian soils potent in the
antibiotics production. Then studying the different factors
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affecting ~ the antibiotic production. The results of this
study could be summarized as follow:
1- In this investigation 865 streptomyces isolates were
obtained from soil samples collected from different areas in
Egypt namely EI-Kalubia. EI-Sharkia. EI-Dakahlia governorates
and then purified on starch nitrate agar medium.
2- Then.the screening of these isolates was carried out
according to their antibiotic activity against the following
test organisms:
B. subtilis; B. cereus; Kl. pneu.onia; staph. aureus;
Sal.typhi.uriu.; E. coli; Candida albicans; Sacch. cerevisiae
and pseudo.anas sp.
72 isolates of streptomyces were selected which produced
antibiotic substances. These isolates obviously inhibited the
growth of the test organisms. Fiqally these strains were
compared with each other in order tc> deteraine the best for
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antibiotic production. Two strains namely stre~tomyces sp.560
I
and streptomyces sp .•720 were selected as the h~ghest producer
of the antibiotic among these strains.
3- B. cereus Kl. pneumonia and ~. typh..!furiumwere the
sensitive test organisms to antibiotics ~roduced by the
most i
two streptomyces strains namely streptomyce~ spp.560 & 720.
So. they were used as test organisms in the su,sequent experiments.
4- In order to determine the best ferm~ntation medium
four media were investigated namelY:
Wheat bran infusion medium, Rice bran ~nfusion medium. !
Wheat straw infusion medium, Corn starc~ nitrate medium
for the antibiotics production by streptomyce~ spp ••560 & 720
I
to select the most suitable one for the antib~otics production I
by the streptomyces isolates. Wheat bran inf4sion medium was !
found to be the best medium for the antibioti.s prodction. So,
this medium was .selected to be used in’ the subsequent
experiments.
5- Modified nutrient agar medium was selected as the
medium for carring out the sensitivity test because it gave
the better growth for the test organisms.
6- Two methods were tested to determine the sensitivity
of the test organisms:
I
A- Holes method B- Disk method
There were no great difference between the results obtained by
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the two methods. So. the disk method was used in the subsequent
experiments because the disk method is easier to perform.
7- The optimum temperature for ·the antibiotic production
by streptomyces sp.,560 was 32 ·c. While that for streptomyces
sp. ,720 was 35·c 0
8- The optimum pH for the antibiotic production by
streptomyces sp .•560 was 7.5. While· that for mtrptomyces
sp .•720 was 7.
9- The optimum fermentabion period for the antibiotic
productin by two strains was 5 days for strgtomyces spo.560.
While that for streptomyces sp •• 720 was 6 days.
10- Results showed that the most suitable concenration of
agar in the medium used for testing the s¢nsitivity of the
test organisms towards the produced antibiotics was 12 gm/1it.
of the medium.
11- Result~ also showed that the starch was the best
carbon source in increasing the antibiotics production by
StretoIDyces spo. 560 & 720.
12- The most suitable concentration of starch for
antibiotic production in the fermentation medium was 12 gm/lt.
for streptomyces sp ••560. while that for ~eptomyces sp ••720
was 10 gm/lit.
13- Results also showed that the amino acid glycine was
the best nitrogen source for antibiotics production by both
the two· Streptomyces strains.
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,,
14- The most suitable concentration of gl~cine for antibiotic
production in the fermentation medium W4- 5 gm/l
it
. for
;
both the two streptomyces strains.
15- The antibiotic production at the op~imum conditions
I
was higher than any of the other treatment6~ , This was found
I
with both the two streptomyces strains. iI
16- The results of the optimum condi~ions experiment
showed that streptomyces sp.,720 seemed t~ be better than
Stre2tomyces sp ••560. So. the antihiotic ~roduced by this
strian was extracted. I
17- The extraction process was carried ~t where different
organic solvents were tested namely: I
N-Putanol. Acetone, Hex.ne, Benze~e, Chloroform,
Ethyl acetate and mixture from chloroform~.:& ethyl acetate.
The results showed that the mixture from chl+roform and ethyl
r
acetate was the best solvent for extracti~g the antibiotic
produced by streptomyces sp.,720.
18- The antibiotic produced by strept~ces sp.,720 was
effective against the investigated plant pat~gens:
Pseudomonas marginalis Brwinia carotovora ~gro. tumifaciens.
19- The heat treatments of the metaboli.c solution showed
that the intermittent heat treatment (BO ·c) for 15 min. for 3
successive days slightly increased the effectiveness of the
antibiotic, while boiling fQr 1 min~ slightly decreased the
effectiveness of the antibiotic, boiling for 5 min. or 10 min.
caused drastic effect Ion the antibiotic.