Citric Acid Fermentation by Locally Isolated Aspergillus Niger M2sg1-Ms4
The citric acid fermentation by locally isolated strain of Aspergillus niger was carried out using shake flask culture and 2 L stirred tank fermenter. The pure strain was obtained through monospores isolation step using spread plate technique. From morphological and biochemical properties, isolat...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2004
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/6746/1/IB_2004_3%281-24%29.pdf |
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| Summary: | The citric acid fermentation by locally isolated strain of Aspergillus niger was
carried out using shake flask culture and 2 L stirred tank fermenter. The pure strain
was obtained through monospores isolation step using spread plate technique. From
morphological and biochemical properties, isolated monospore M2sgl -MS4 can be
suggested belong to the strain Aspergillus species.
Optimization of fermentation medium for citric acid production by the locally
isolated A. niger M2Sgl-MS4 was achieved using 200 g/L of glucose and 0.8 g/L
of ammonium nitrate. Addition of 3% (vfv) methanol to the optimized medium
improved citric acid production (62.5 glL) by about two times higher compared to
control. Trace elements used were similar to the trace elements used in a
fermentation medium described by Osthman et al. (1 999). Optimum fermentation
condition for citric acid production by M2sgl-MS4 was obtained at initial pH range
between 2.5-3.0, temperature of 30°C and agitation speed of 1000 rpm with 1.0
vvm airflow rate. Maximum citric acid concentration obtained under this condition was approximately 62.5 g/L, which gave the yield and overall productivity of 0.41
glg and 0.19 g/L/h, respectively.
Foaming is one of the problems normally encountered in submerged fermentation
using bioreactor as a result of bubble aeration. In order to find approach for
minimizing foam formation during citric acid fermentation in stirred tank
fermenter, the effect of several fermenter configurations based on number of
impeller and baffles used on foam formation tested. The fermenter with 4-baffles
and a single Rushton turbine impeller was found suitable to avoid excessive
foaming during the fermentation.
The development of dissolved oxygen tension (DOT) control strategies aimed at
improving citric acid production in 2 L stirred tank fermenter was also carried out.
Maximum citric acid production was obtained in batch fermentation in which DOT
was controlled at 80% saturation through out the fermentation. Approximately,
69.06 g/L citric acid which gave yield and overall productivity of 0.47 g/g and 0.22
g/L/h respectively was obtained after 3 12 h of fermentation. This result indicates
that the high DOT was needed for high glucose conversion to citric acid throughout
the fermentation process. |
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