الفهرس 
Materials and mithodsOnly 14 pages are availabe for public view
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Abstract
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SUMMARY
Actinomycetes espeoially members of the genus streptomyces
produoe several valuable biologioally active substances such as
enzymes, vitamins growth stimulators, pigments, toxins and
antibiotics. Antibiotics are very important for plant, human,
animals, poultry as therapeutic agents against different kinds
of diseases. Therefore, this study was carried out to search
for streptomyces isolate from the Egyptian soils, potent in the
antibiotics production. Then studying the different factors
affecting the antibiotics production. The results of the study
could be summarized aa follow :
1. In this investi, gation 890 streptomyces isolates were
obtaind from samples oolleoted from different areas in
Egypt, namely EI-Kalubia, El-Sharkia, El-Dakahlia, EI-Beheira,
Kafer El-Shaikh and Demyatta governorates. These isolates
were purified on staroh nitrate agar then maintained on the
o
same medium at 4-5 C .
2. Soreen1Jlg of streptomyces isolates was made according to
their antibiotio activity against the following test
organisms :
Staphylococcus aur,us, Klebsiella pneumonia, Bacillus,
cereus. Salmonella typh1murium. Sarcina lutea, Escheriohia
co11 and Candida Mbicans.
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Seventy one strains of streptomyces were selected which
produced antibiotic substances, and clearly inhibited the
growth of the test organisms. Finally, these strains were
compared with each other to determine the most antibiotic
producer. Two strains namely Streptomyces~. (818) and
Streptomyces~. (813) were selected as the highest producer
of the a.ntibiotics among the other investigated
strains.
’fwo organisms namely xi , Imewnonia and !!. cereus
were selected, among the other investigated test organisms,
which were the most sensitive to antibiotic substances
produced by StreptoffiYcas~. (818) and Streptomyces ~.
(873). Modified nutrient agar medium was selected as the
medium of choice for carrying out the sensitivity teat
siBce it gave the best growth of the test organisms.
Selection of the fermentation medium :- -------------------~-~-------------
~’ive media na.ely wheat straw infusioll, wheat bran
infusion,corn starch nitrate, rice bran infusion and
Barseem straw infua10n were investigated for the antibiotic
production bi streIfOmyC8s~. (818) and StreptOmYces ~.
(873) to select the most suitable one. Wheat bran Lnfus10n
was fou.nd to be toe best medium for the antibiotic productiOA.
So, ’this ••••. um was selected to be used i.D the
following experimea~s.
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5. ~he sensi~1vity test was carried out by the cup method
and the disc method. No great differences were found
between the results obtained by the two methods. So the
disc method was used in the following experiments because
it is easier to perform.
6- Results also showed that the most suitable concentration
of agar in the medium used for testing the sensitivity
of the test organisms towards the produced intibiotics
was 9-12 gram agar/litre of the medium. This level of
agar permitted more diffusion of the antibiotic which
caused wider inbibiotion zone.
1- The optimum temperature for the antibiotic produ.ction by
o
Streptomyces ~. (818) was 26 0, while that for Streptomyces
o
~. (813) was 31 C.
8. The optimwn pH for tbe antibiotic production was found to
be ~ for both the two strains of streptomyces.
9. The optimum fermentation period for the antibiotic production
by an.y of the 1wo Streptom.yces strains was found to
be 9 days.
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10. Different carbon sources namely starch. glycerol. maltose,
lactose, fructose, sucrose. substituted glucose in wheat
bran infusion medium (control). Results showed that starch
was the best carbon source in increasing the antibiotic
production by Streptomyces ~. (818) and Streptomyces ~.
(87.3).
11. The most suitable concentration of starch for antibiotic
production in the fermentation medium was 8 gm/L. for
Streptomyces~. (818) and 10 emiL for Streptomyces ~.
(87.3) •
ll. Different nitrog,en sources namely ammonium sulphate, LAsparagine,
potassium nitrate, ammonium chloride, magnesium
nitrate and urea substituted peptone in the wheat bran
infusion medium. itesults showed that L-asparagine was 8Uperior
to peptone in increasing the antibiotic.
13. The concentration of L-asparag1nlwhich produced the greatest
amount of the antibiotic was found to be 5 gram of LAsparaginel
L ot the aedium.
14. The antibiotic production at all optimum condi tiona was
higher than any of -.ae other treatments this was found with
both the two strept-.yces strains.
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