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  3. d a fermenter has been contaminated by a foreign microbe...

Question: d a fermenter has been contaminated by a foreign microbe...

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(d) A fermenter has been contaminated by a foreign microbe (i.e. a microbe other than the production strain). Select all answers from the following list that could be responsible for the invasion of the contaminating microbe. i) Inadequate sterilisation of the fermenter vessel.

ii) Addition of growth medium that had been heat-treated just enough to kill all the vegetative microbial cells.

iii) Cross contamination occurred during preparation of the cryopreserved culture used to produce the inoculum. iv) Insufficient concentration of the nitrogen source in the growth medium.

v) A sample taken from the fermenter was subsequently handled under non-aseptic conditions.

vi) Depth filter used to treat air sparged into the fermenter is wet.

(3 marks)

(e) The following figure shows characteristic batch growth curves according to two different mathematical models. Choose the best answer from the following two options:

a) Series 1 represents a bacterial fermentation and Series 2 represents a filamentous fungal fermentation.

b) Series 2 represents a bacterial fermentation and Series 1 represents a filamentous fungal fermentation.

(2 marks)

(f) An anabolic, growth-associated product is to be produced from glucose as a substrate by a heterotrophic facultative anaerobic microbe. If the microbes were grown anaerobically, rather than aerobically, the product yield from substrate would be:

i) Higher

ii) Lower

iii) The same

(2 marks)

(g) For a given microorganism, which form of continuous culture would be practically limited to operating at the lowest dilution rate?

i) Chemostat with immobilised cells

ii) Chemostat suspension culture

iii) Chemostat with cell recycle

iv) Turbidostat

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