250+ TOP MCQs on Microbial Fermentation and Answers

Chemical Reaction Engineering Interview Questions and Answers for Experienced people 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

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

2. 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

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

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} )

Answer: a
Clarification: 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

Answer: b
Clarification: 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} )

Answer: c
Clarification: 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}. )

6. 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

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

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

Answer: a
Clarification: 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

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