250+ TOP MCQs on Microbial Fermentation and Answers Pdf

Chemical Reaction Engineering Multiple Choice Questions on “ Microbial Fermentation”.

1. State true or false.
Kinetics of microbial fermentation cannot be expressed by Monod kinetics.
a) True
b) False

Answer: b
Clarification: The growth rate of microbial cells is given by Monod kinetics.
Rate of growth r_C = (frac{kC_A C_C}{C_A+ C_M}.) The reaction is A (^{underrightarrow{C}}) C + R. The substrate in the presence of microbial cells gives more cells and the waste, R.

2. The fractional yield of C with respect to A for the reaction A (^{underrightarrow{C}}) cC + rR is the ratio of ____
a) All R formed to all A reacted
b) All A reacted to all R formed
c) All A reacted to all C formed
d) All C formed to all A reacted

Answer: d
Clarification: Fractional yield is the ratio of product formed to the total reactant fed. It is the ratio of all C formed to all A reacted.

3. The hierarchy of phases for the microbes in a fermentation process is ____
a) Exponential growth phase → Lag phase → Stationary phase → Death phase
b) Stationary phase → Lag phase → Exponential growth phase → Death phase
c) Lag phase → Exponential growth phase → Stationary phase → Death phase
d) Lag phase → Stationary phase → Exponential growth phase → Death phase

Answer: c
Clarification: There is an initial lag phase for the microbial cells to begin growth and reproduction. The cells then grow exponentially and there exists a stationary growth less phase. Eventual death of cells is observed due to depletion of food.

4. The substrate limiting kinetics of A (^{underrightarrow{C}}) C + R is the one in which ___
a) Final concentration of C depends on initial amount of food
b) Final concentration of C does not depend on initial amount of food
c) Final concentration of C does not exceed a certain value
d) The rate depends on enzyme concentration

Answer: a
Clarification: The amount of food determines the progress of the reaction. Product does not affect the reaction rate.

5. The poison limiting kinetics of A (^{underrightarrow{C}}) C + R is the one in which ___
a) Final concentration of C depends on initial amount of food
b) Final concentration of C does not depend on initial amount of food
c) Final concentration of C does not exceed a certain value
d) The rate depends on enzyme concentration

Answer: c
Clarification: The product slows down the reaction. After sometime, the product concentration increases and the reaction cease to occur.

6. The relationship between the Monod rate constant, k and the rate constant observed due to waste accumulation k_obs is ____
a) k_obs = k (1-(frac{C_R}{C_R^*}))ⁿ
b) k_obs = k (1-(frac{C_R}{C_R^*})^frac{1}{n})
c) k = k_obs (1-(frac{C_R}{C_R^*}))ⁿ
d) k_obs = k ((frac{C_R}{C_R^*}))ⁿ
C_R* is the concentration of R where cell activity stops and n is the order of product poisoning.

Answer: a
Clarification: k_obs = k (1-(frac{C_R}{C_R^*}))ⁿ
The buildup of harmful wastes interferes with the cell multiplication. The observed rate constant decreases with a rise in C_R.

7. In a batch fermenter, for substrate limiting kinetics, C_C,max is ________
a) Independent of C_A0
b) Directly proportional to C_A0
c) Inversely proportional to C_A0
d) Proportional to the square of C_A0

Answer: b
Clarification: At low C_A0, C_C,max α C_A0. For high C_A0, C_C,max is independent of C_A0.

8. With an accumulation of waste formed during the reaction, the value of observed Monod rate constant ____
a) Decreases
b) Increases
c) Remains constant
d) First decreases and then increases

Answer: a
Clarification: The accumulation of waste formed decelerates the reaction rate. This decrease is reflected in the reaction rate constant.