# Downstream Processing Questions and Answers

## Multiple Choice Questions (MCQ) and Answers on Downstream Processing

Question 1: For the extractions operation, the selectivity should be

1. >1
2. <1
3. zero

Question 2: The purity of a solute collected between two times t1 and t2 during chromatographic separation can be calculated as

1. amount of solute eluted – amount of impurity eluted
2. amount of solute eluted / amount of impurity eluted
3. amount of solvent eluted + amount of impurity eluted
4. amount of solvent eluted / amount of impurity eluted

Question 3: Chromatography is based on the

1. different rate of movement of the solute in the column
2. separation of one solute from other constituents by being captured on the adsorbent
3. different rate of movement of the solvent in the column
4. any of the above

Question 4: The correlation often employed to correlate adsorption data for protein is (where Ymax is the maximum amount of solute adsorbed per mass of adsorbent, X is the mass fraction of solute in the diluent phase in solute-free basis, KL is a constant and Y is the equilibrium value of the mass of solute adsorbed per mass of adsorbent)

1. Y = YmaxX/(KL+X)
2. Ymax/(KL+X)
3. YmaxX/KL
4. Y = Ymax– X/ (KL+X)

Question 5: A typical tubular centrifuge has a bowl of 2 to 5 inch in diameter and 9 to 30 inch in height with a maximum rotating speed of

1. 15,000 to 50,000 rpm
2. 50,000 to 100,000 rpm
3. 100,000 to 150,000 rpm
4. 150,000 to 200,000 rpm

Question 6: For cost analysis in a fermentor system, the depreciation cost varies from

1. 5-6% of the capital cost
2. 6-7% of the capital cost
3. 6-10% of the capital cost
4. 8-10% of the capital cost

Question 7: Micro filtration refers to the separation of suspended material such as bacteria by using a membrane with spore sizes of

1. 0.02 to 10μm
2. 1-10A°
3. 20-30μm
4. 10-200A°

Question 8: Start up expenses in a fermentation industry varies from

1. 0-5% of the capital cost
2. 10-15% of the capital cost
3. 5-10% of the capital cost
4. 15-20% of the capital cost

Question 9: The solvent flux across the membrane can be expressed as (where A is the area, Lp is the membrane permeability, σ is the reflection point, Δp is applied pressure and Δπ is the osmotic pressure)

1. J = Lpp – σΔπ)
2. J/A = Lpp – σΔπ)
3. Lp/σΔπ
4. J/A = Lpp

Question 10: Which of the following is considered as a pretreatment to the biological feeds?

1. Heating to denature the proteins
2. Addition of filter aids to increase the porosity
4. All of the above

Question 11: If the solute passes through membrane freely, the the rejection coefficient (s) is

1. 1
2. 0
3. >1
4. <1

Question 12: If the membrane rejects all solute, the rejection coefficient (s) is

1. 1
2. 0
3. >1
4. <1

Question 13: In antibiotic manufacturing processes, the fermentation time ranges from

1. 2-3 weeks
2. 1-2 weeks
3. 4-5 weeks
4. 2-4 weeks

Question 14: The conventional filtration involves the separation of large particles generally

1. dp>5μm
2. dp>10μm
3. dp>15μm
4. dp>20μm

Question 15: Which of the operation does not come under upstream processing?

1. Media preparation
2. Inoculum development
3. Effluent treatment
4. Storage of raw material

Question 16: The disk centrifuge is the type of centrifuge used most often for bio separations due to its

1. continuous operation
2. lesser cost
3. higher speed
4. ease in operation

Question 17: The effectiveness of a solvent can be measured by the

1. distribution coefficients
2. selectivity
3. both (a) and (b)
4. diffusivity

Question 18: The stage wise operation of adsorption is called

1. contact filtration
4. ion exchange

Question 19: Which of the following is not the physical method for the cells rupturing?

1. Milling
2. Homogenization
3. Ultrasonication
4. Enzymatic digestion

Question 20: Conventional adsorption is a

1. reversible process
2. irreversible process
3. either reversible or irreversible
4. none of these

Question 21: Maintenance cost varies from

1. 0-4% of the capital cost
2. 12-16% of the capital cost
3. 4-8% of the capital cost
4. 8-12% of the capital cost

Question 22: The optimum wet solid content for the cell suspension for a bead mill is typically somewhere between

1. 5-15% by volume
2. 15-30% by volume
3. 30-60% by volume
4. 60-90% by volume

Question 23: Assuming the laminar flow across the filter, the rate of filtration (dVf/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 is the thickness of the filter cake)

2. dVf/dt = (1/A)Δp/μ(L/K)
4. dVf/dt = (1/A)Δp/μ LK

Question 24: Filtration leaf test results indicate that the filtration rate of a protein product is 100 dry lbs/(ft2hr). What size production filter would be required to obtain 100 dry lbs of filter cake/hr?

1. 1.54 ft2
2. 3.08 ft2
3. 65 ft2
4. 65 lbs/ ft2.hr

Question 25: Selectivity can be expressed as

1. ratio of the distribution coefficients in different solute
2. mass fraction of the solute in the extract phase at equilibrium
3. mass fraction of the solute in the raffinate phase
4. ratio of the mass fraction of the solute in the extract phase to the raffinate phase

Question 26: Concentration polarization can be reduced further by

1. pre filtering the solution
2. reducing the flow rate per unit membrane surface area
3. back washing periodically
4. all of the above

Question 27: A system which require less solvent and produces a more concentrated extract phase, is desired with a

1. large distribution coefficients
2. small distribution coefficients
3. very small distribution coefficients
4. constant distribution coefficients

Question 28: The efficiency of cell disruption in a bead mill depends on the

1. concentration of the cells
2. amount and size of beads
3. type and rotational speed of agitation
4. all of these

Question 29: A common filter medium is the cloth filter generally made of

1. canvas
2. synthetic fabrics
3. metal or glass fiber
4. all of these