# Downstream Processing – Section 1

6. Maintenance cost varies from

A. 0-4% of the capital cost
B. 12-16% of the capital cost
C. 4-8% of the capital cost
D. 8-12% of the capital cost

Correct Answer: C. 4-8% of the capital cost

7. The optimum wet solid content for the cell suspension for a bead mill is typically somewhere between

A. 5-15% by volume
B. 15-30% by volume
C. 30-60% by volume
D. 60-90% by volume

Correct Answer: C. 30-60% by volume

8. Assuming the laminar flow across the filter, the rate of filtration (dV f/dt) can be expressed as a function of pressure drop Dp by the modified D‘Arcy’s equation as (where A is the area of filtering surface, K is the D‘Arcy’s filter cake permeability and L is the thickness of the filter cake)

A. (1/A) dV f/dt = Δp/μ(L/K)
B. dV f/dt = (1/A)Δp/μ(L/K)
C. (1/A) dVf/dt = Δp/μ LK
D. dV f/dt = (1/A)Δp/μ LK

Correct Answer: A. (1/A) dV f/dt = Δp/μ(L/K)

9. Filtration leaf test results indicate that the filtration rate of a protein product is 100 dry lbs/(ft2 hr). What size production filter would be required to obtain 100 dry lbs of filter cake/hr?

A. 1.54 ft2
B. 3.08 ft2
C. 65 ft2
D. 65 lbs/ ft2.hr