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Industrially Useful Microbial Processes Questions and Answers

1.

Which of the following components prevents vortex formation in a fermenter ?

Exam Year(s)

MH SET - 2018, SET Exam - 2018,

Answer: C

Vortex formation is prevented by the baffle (spelt Bafle in the paper).

Baffles are vertical metal strips fixed to the inner wall of a stirred fermenter, usually four of them. Without them the impeller would set the whole broth spinning, forming a central vortex that reduces mixing and oxygen transfer and can draw air down to the impeller. The baffles break up this swirling flow and turn it into the turbulent mixing that keeps cells, nutrients and air bubbles evenly spread.

The sparger introduces air at the bottom of the vessel. The impeller (and a propeller, one kind of impeller) does the stirring, and is in fact what creates the vortex the baffles prevent.

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2.

The enzyme useful in conversion of penicillin G to 6-aminopenicillonic acid is :

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: A

The enzyme is penicillin acylase.

Penicillin acylase (penicillin amidase), from E. coli and other bacteria, cuts the amide bond that joins the phenylacetyl side chain to the penicillin nucleus. This converts penicillin G into 6-aminopenicillanic acid (6-APA, printed 'penicillonic'), the core to which new side chains are attached to make semi-synthetic penicillins such as ampicillin.

Penicillinase (β-lactamase) opens the β-lactam ring instead and inactivates the drug. Carboxypeptidase and aminopeptidase remove amino acids from the ends of peptides.

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3.

For thorough mixing of medium and inoculum the part of the fermentor useful is :

Exam Year(s)

MH SET - 2019, SET Exam - 2019,

Answer: C

The mixing part is the impeller.

The impeller is the set of blades, usually Rushton turbines, mounted on the central shaft of a stirred-tank fermentor. As it turns, it mixes medium and inoculum thoroughly, keeps cells in suspension, breaks air bubbles into fine ones and spreads heat evenly.

The shaft only carries the impeller and transmits the motor's drive. The sparger releases air into the medium, and the headspace is the empty volume above the liquid.

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4.

In fermentor, the top portion left without broth is called :

Exam Year(s)

MH SET - 2021, SET Exam - 2021,

Answer: B

The top portion left without broth is the headspace.

A fermentor is not filled completely. Typically 20 to 25% of the vessel volume is left empty above the liquid. The headspace takes the foam that forms on aeration, lets gas separate from the broth before it leaves through the exhaust, and gives a margin for volume increase during the run.

The other three are parts inside the broth. The shaft carries the agitator, the impeller is the stirring blade mounted on it, and the sparger is the perforated pipe that bubbles air into the medium at the bottom.

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