Question 19N.3.HL.TZ0.10
| Date | November 2019 | Marks available | [Maximum mark: 6] | Reference code | 19N.3.HL.TZ0.10 |
| Level | HL | Paper | 3 | Time zone | TZ0 |
| Command term | Distinguish, Explain, Identify, Suggest | Question number | 10 | Adapted from | N/A |
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]
blackwater
OR
brownwater/sewage
OR
feces
OR
organic solid waste
OR
paper pulp
OR
other biodegradable material ✔
Do not accept methane and CO2.
Identify the ideal temperature and oxygen conditions inside the fermenter for efficient biogas production.
Temperature:
Oxygen:
[1]
temperature: warm
oxygen: low/anaerobic ✔
Both required.
Distinguish between batch and continuous culture fermentation.
[2]
a. in batch culture product is withdrawn at the end of the «organisms » growth phases whereas in continuous culture product is withdrawn while the organism is growing / OWTTE ✔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 ✔
Explain how conditions in the fermenters are maintained to maximize penicillin production.
[2]
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.