# Fermentation Technology Questions and Answers – Aeration and Agitation – Determination of Kla Values

This set of Fermentation Technology Multiple Choice Questions & Answers (MCQs) focuses on “Aeration and Agitation – Determination of Kla Values”.

1. Which of the following is not a fermenter?
a) Bioflo
b) Biostat B
c) New Brunswick
d) Blustar

Explanation: The famous well-known fermenters are Bioflo series, the B. Braun Biostat B fermenters, New Brunswick. These are all equipped with a dissolved oxygen meter.

2. The rate of oxygen tranfer is given by equation ____________
a) dCL/dt = KLa (C* – CL)
b) dCL/dt = KLa (C*)
c) dCL/dn = KLa (CL)
d) dCL/dn = KLa (C* – CL)

Explanation: The rate of oxygen transfer from air bubble to liquid phase is described as: dCL/dt = KLa (C* – CL) where, CL is the concentration of DO in fermented broth, dCL/dt is the change in oxygen concentration over a period of time, KL is the mass transfer coefficient, a is the gas/liquid interface area per liquid volume, C* is the saturated DO concentration.

3. The unit of KLa is __________
a) cm2
b) h-1
c) cm3
d) cm h-1

Explanation: The unit of the volumetric mass-transfer coefficient is h-1. It is very difficult to determine the value of KL and a alone, that is why it is also measured together. The unit of KL is cm h-1 and that of a is cm2 cm-3. Therefore, the unit of KLa is h-1.

5. Which of the following is the method of determination of KLa values?
a) Oxygen-balance technique
b) Sulphite oxidation technique
c) Static method of gassing out
d) Dynamic method of gassing in

Explanation: The dynamic method of gassing-in is not a method of determination of the values of KLa. The KLa determination includes the Sulphite oxidation technique, Oxygen-balance technique, and gassing-out techniques.

6. Who described the sulphite oxidation technique?
a) Cooper
b) Humphrey
c) Wise
d) Taguchi

Explanation: Cooper et al. in 1944 were the first to describe the sulphite oxidation technique for the determination of KLa values. He determined the OTR in aerated vessels by oxidation of sodium sulphite solution.
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7. Which of the following does not require the measurement of DO concentration?
a) Oxygen-balance technique
b) Sulphite oxidation technique
c) Static method of gassing out
d) Dynamic method of gassing out

Explanation: The sulphite oxidation balance technique does not require the measurement of dissolved oxygen concentration. It depends on the rate of conversion of sodium sulphite solution to sodium sulphate solution in the presence of a catalyst.

8. Which of the following is not a surface active contaminant?
a) Proteins
b) Fatty acids
c) Nucleic acids
d) Lipids

Explanation: The surface active contaminants include proteins, amino acids, fatty acids, lipids, esters, etc. It has a major effect on the accuracy of sulphite oxidation technique.

9. Who described the static method of gassing-out?
a) Cooper
b) Humphrey
c) Wise
d) Taguchi

Explanation: Wise in 1951 was the first to describe the static method of gassing-out. The technique was used in the measurement of KLa values where the concentration of oxygen is lowered by gassing out with the nitrogen gas.

10. Which of the following was used to gas out oxygen in the dynamic method of gassing-out?
a) Growing culture
b) Nitrogen gas
d) Helium

Explanation: The growing culture was used to gas out the oxygen in the dynamic method of gassing-out. The culture utilized all the oxygen by respiring in the fermenter for their growth and simultaneously the aeration was also stopped.

11. Who described the dynamic method of gassing out?
a) Cooper and Humphrey
b) Humphrey and Taguchi
c) Wise and Schwan
d) Taguchi and Schwan

Explanation: Taguchi and Humphrey in 1996 described the dynamic method of gassing out. They utilized the respiratory growing culture in the fermenter to lower the oxygen level in the fermenter before the aeration was provided.

12. Which of the following is not a measuring parameter in oxygen-balance technique?
a) Area of the vessel
b) Temperature
c) Pressure
d) Volume

Explanation: The oxygen-balance technique involves the measurement of the parameters such as the temperature of gases at inlet and outlet, volume of broth in the vessel, air flow rate at inlet and outlet, mole fraction of oxygen at the inlet and outlet, the pressure at the fermenter inlet and outlet.

13. The oxygen balance technique is used for gas-gas transfer.
a) True
b) False

Explanation: The oxygen balance technique is used for gas-liquid transfer mass transfer and is used for the measurement of the KLa values. It involves the measurement of several parameters such as temperature, pressure, etc.

14. The above Crit value is the efficient value for oxygen concentration.
a) True
b) False

Explanation: The Crit value is the critical value of the volumetric oxygen transfer coefficient. The value should be above critical value so that uptake of oxygen by the culture is not dependent or independent of the concentration of oxygen.

15. Who claimed that oxygen balance technique is suitable for only small-scale fermenters?
a) Cooper
b) Humphrey
c) Wang
d) Taguchi

Explanation: Wang et al. in 1979 claimed that oxygen balance technique is suitable for only small-scale fermenters because, at a large-scale, the difference in dissolved oxygen concentration may be up to a larger extent with inlet and outlet gases.

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