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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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Option B: Biotechnology and bioinformatics » Option B: Biotechnology and bioinformatics (Core topics)
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