Food & Nutrition

Arab Journal of Food & Nutrition
41. Citric Acid Production by Selected Aspergillus Species Using Whey as
Fermentation Medium (1999)
Murad Ahmad El. Holi\ University of Jordan
Supervisor: Dr. Khalaf Soofi Al-Delaimy
Citric acid (CA) production by strains of Aspergillus using cheese whey, as
fermentation medium supplemented with different additives (during fermentation time
of 12-20 days at temperature of 30 ± 2°C) was studied. It was found that among three
strains of Aspergillus used in this study (A. niger ATCC 9642, A. niger ATCC 6275
and A. foeitidus ATCC 10254) using two synthetic media and whey alone, A. niger
ATCC 9642 was most efficient for CA production and thus was used further in this
study.
Supplementation trials of whey with different concentrations of date juice (11.5,
16.5 and 21.5% T.S,S in whey) plus 2% tricalcium phosphate and 4% methanol in a
surface culture, revealed that whey containing 21.5% T.S.S with a combination of 2%
T.P + 4% methanol was found to be the most efficient media for CA production (31.64
g/1) after 10 days of cultivation. Surface culture process was found to be much more
favorable for CA production than submerged culture process.
Media containing whey in different concentrations (5, 10 and 15% (w/v) of four
sugars (sucrose, glucose, fructose and galactose) were used for CA production. Whey
media containing 15% sucrose were found to produce the highest CA (106.05 g/l).
Whey containing 15% sucrose and 1% methanol was also efficient medium for CA
production with a value similar to that of whey and 15% sucrose. Biomass dry weight
values of these two media were 37.4 and 33.9 g/l respectively. Higher biomass values
(42.2-46.0 g/l), with relatively lower CA produced, were obtained in the whey media
containing 15% sucrose with 10-50 mg/I riboflavin.
The relationship between CA production, residual sugars, biomass and pH in the
whey media containing 15% sucrose was studied. The highest CA and biomass in this
medium were produced after 16 days cultivation (83.71 g/l and 36.3 g/l respectively).
Both residual sugars and pH values decreased from 173.8 g/l to 48.9 g/I and from 3 to
1.5 after 16 days cultivation, respectively.
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