250+ TOP MCQs on Microbial Fermentation – 2 and Answers

Chemical Reaction Engineering Interview Questions and Answers for Experienced people focuses on “Microbial Fermentation – 2”.

1. State true or false.
For product limiting microbial fermentation in CSTR with C_C0=0, C_R0=0 and high C_A0, washout occurs at kτ =1.
A. True
B. False
View Answer

Answer: A
Explanation: Maximum production of cells occurs at kτ =2. The concentration at which maximum production rate occurs is C_R = (frac{C_R^*}{2}.)

3. The slope of the curve of (frac{C_C}{r_C}) and (frac{1}{C_A}) for the substrate limiting microbial reaction in a batch reactor is ____
A. (frac{C_M}{k} )
B. (frac{1}{k} )
C. –(frac{C_M}{k} )
D. –(frac{1}{k} )
View Answer

Answer: A
Explanation: The equation representing the kinetics is, (frac{C_C}{r_C} = frac{1}{k} + frac{C_M}{k}frac{1}{C_A}.) The slope is (frac{C_M}{k} ) and the line intercept is (frac{1}{k}. )

4. The plot of (frac{1}{C_A}) and τ for mixed flow substrate limiting fermentation reaction in fermenters, assuming no cells in feed stream is ___
A. Quadratic
B. Linear
C. Logarithmic
D. Exponential
View Answer

Answer: B
Explanation: The relationship between C_A and τ for mixed flow fermenter with C_C0=0 is (frac{1}{C_A} = frac{k}{C_M}) τ – (frac{1}{C_M}.) The plot is linear with a slope (frac{k}{C_M}. )

5. Optimum operations for CSTR carrying out substrate limiting fermentation reaction occurs at ___
A. τ = (frac{N}{N-1} )
B. kτ = (frac{N-1}{N} )
C. kτ = (frac{N}{N-1} )
D. kτ = (frac{N^2}{N-1} )
View Answer

Answer: C
Explanation: The maximum operation for a single mixed flow fermenter occurs at (frac{C_A}{C_{A0}} = frac{1}{N+1}.) kτ = (frac{N}{N-1}. )

7. Given the value of τ_opt for product limiting microbial fermentation is 2 hrs, then the value of τ_washout (in hour) is ____
A. 1
B. 2
C. 3
D. 4
View Answer

Answer: A
Explanation: τ_opt = 2τ_washout.
τ_washout = 1 hour.

8. If C_A0 = 8 and C_M = 1, the value of N is ____
A. 4
B. 1
C. 2
D. 3
View Answer

Answer: D
Explanation: N = (1+(frac{C_{A0}}{C_M}))^0.5 = (1+(frac{8}{1}))^0.5 = 3.

9. The value of C_R,opt for product limiting microbial fermentation (in kg/m³), given the value of C_R*=60 kg/m³ is ____
A. 30
B. 20
C. 15
D. 10
View Answer

Answer: A
Explanation: C_R,opt = (frac{C_R*}{2} = frac{60}{2}) = 30 kg/m³.

10. The value of τ_m,washout given N = 4 and k=1 is____
A. 1.06
B. 1.34
C. 2.45
D. 3.86
View Answer

Answer: A
Explanation: τ_m,washout = (frac{N^2}{(N^2-1)k} = frac{16}{15}) = 1.06