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Date November 2019 Marks available 1 Reference code 19N.3.HL.TZ0.10
Level Higher level Paper Paper 3 Time zone TZ0 / no time zone
Command term Identify Question number 10 Adapted from N/A

Question

The diagram below represents a small-scale biogas fermenter.

[Source: © Science in Society. http://www.i-sis.org.uk/BiogasChina.php]

Suggest one material that could be loaded into the biogas fermenter from which biogas can be produced.

[1]
a.

Identify the ideal temperature and oxygen conditions inside the fermenter for efficient biogas production.

Temperature:

Oxygen:

[1]
b.

Distinguish between batch and continuous culture fermentation.

[2]
c.

Explain how conditions in the fermenters are maintained to maximize penicillin production.

[2]
d.

Markscheme

blackwater
OR
brownwater/sewage
OR
feces
OR
organic solid waste
OR
paper pulp
OR
other biodegradable material ✔

Do not accept methane and CO2.

a.

temperature: warm
oxygen: low/anaerobic ✔

Both required.

b.

a. in batch culture product is withdrawn at the end of the «organisms » growth phases whereas in continuous culture product is withdrawn while the organism is growing / OWTTE

b. in batch culture all of the growth medium/nutrients are added at the beginning whereas in continuous culture, growth medium/nutrients are added at a constant rate / OWTTE

c. batch culture is carried out in large scale fermenters whereas continuous culture could be in small scale ✔

d. continuous can run for a longer time than batch ✔

c.

a. aerobic conditions achieved by stirring/aeration ✔

b. buffers maintain pH ✔

c. moderate temperatures maintained by cooling jacket ✔ Accept mention of 20-30°C.

d. product is collected during stationary phase ✔

Award marks for identification of the factor and description of the effect.

d.

Examiners report

[N/A]
a.
[N/A]
b.
[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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