الفهرس 
Material and methodsOnly 14 pages are availabe for public view
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Abstract
v- SUMMARY
Citric acid is used in food industries such as soft
drinks, candies, flavouring extracts; in pharmacy and
smallar sm o un t s as ingredients in ink, in dyeing, printing
and silvering agent.
This work was carried out for citric acid production
by local strains of ~. niger and study various factors
affecting the citric acid production. The study revealed
the following results:
1- Screen Lng of the local citric acid producers. The
isola t,~s of ~ niger stra in s were sc re ened for cit ric
acid production. Most active strains were selected
for the study. A strains of ~ niger (AS) gave the
best c.Lt r I n acid production among the other investigated
~trains.
2- The USI~ of diluted molasses (to give 15% sugar) as a
medium gave
weight. On
low citric acid yield and low mycelial dry
addition of the maj or inorganic nutrients
of BerJlhauer’s medium (NH4N03, 2 giL; KH
Z
P0
4
, 1 giL;
MgSO4.7120, 0.25 giL), to the molasses medi urn inc reased
ci~ric acid production.
3..~..The. chemical analysis showed that molasses was very poor
in nutrient elements but contained high ash, iron and.
zinc wt:ich exerted deleterious effect on citric acid
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fermentation.
The addition of the beet molasses ash
to Bernhauer’s medium decreased citric acid yield.
Tr ea t m enr; of molasses to reduce the deleterious effect
of ash elements on citric acid production as the following:
A- Dilut:.on of molasses: The best dilution of molasses
to give the highest yield of citric acid was to 15%
sugar.
B- Different types of alcohols such as methanol, ethanol
and isopropanol were added to molasses medium to increase
citric acid yield. Addition of ethanol stimulated citric
acid I roduction. It was found that 2% ethanol was the
optimun concentration which gave the best yield of citric
acid. The proper time for addition of ethanol was from
commen :ement of fermentation up to 72 hr and the most
sui tab le time for its addition was after 24 hr from
inoculation (yield, 49.2%, conversion coefficient,
53.2%),
c- The u~e of potassium ferrocyanide at a concentration
of 1 giL for precipitating excess heavy metals gave
yield :4%, conversion coefficient 58%).
D- The
6-8
adj ustment
wa s found
of
to
the pH 0 f the molasses med iurn from
be the best range for citric acid
production.
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The study showed that beet molasses which is a byproduct
Jf Sugar industry can be Used economically j n the
citric a c i d production by strains of ~ niger when the
beet mol::tsses medium was treated by the following two
methods:
1- The beEt molasses Was diluted to 15% sugar and Bernhauer’s
inorganic nutrients were added and pH was adj Usted to
pH 7, :’% ethanol was added to molasses med ium from the
commencpment of fermentation up to 72 hr s ,
The most
SUitablE addition time was after 2/, h r s (Yield, 63.1%.
conversion coefficient, 69.08%).
2- The bee’ molasses was dil u t e d to 15% Sugar and the
Bernhaue. ’s inorganic nutrients were added and pH was
adj Usted to 7, I giL potassium fcrrocyanide was added
to molasses medium. The Yield (69.9%),
Coefficielt (75.5%) were scored. conversion