| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.HL.TZ2.9 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 2 |
| Command term | Distinguish | Question number | 9 | Adapted from | N/A |
Question
Distinguish between batch fermentation and continuous fermentation.
[2]
c.
Aspergillus niger is used to produce citric acid by continuous fermentation. Glucose is converted to pyruvate by glycolysis. Trehalose-6-phosphate normally inhibits hexokinase, an important enzyme in the glycolysis pathway.
Suggest how pathway engineering could be used to address this factor which reduces yields of citric acid.
[2]
d.
Markscheme
c.
a. «genetically modify to» incorporate gene for low/blockage of TPS activity into A. niger
b. «genetically modify to» incorporate gene that breaks down trehalose-6-phosphate
c. selectively breed A. niger cultures for low/no TPS activity
d.
Examiners report
[N/A]
c.
[N/A]
d.
Syllabus sections
Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics) » B.1 Microbiology: organisms in industry
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