Download DEPARTMENT OF BIOTECHNOLOGY VI SEM B.E. Biotechnology

DEPARTMENT OF BIOTECHNOLOGY
VI SEM B.E. Biotechnology -- II SESSIONAL TEST
BIO 304: DOWNSTREAM PROCESSING IN BIOTECHNOLOGY
Conducted on 16.03.09
(1545-1645)
TIME: 60 min
Answer all the questions
MARKS: 20
1. I hope u remember cake washing. Explain what will happen if r = 0 and r = 1 during
washing? (0.5+0.5)
2. What is meant by Sigma factor in a centrifuge? (1)
3. For settling in bioseparations we usually take Stoke’s regime not Newton’s regime.Why? Write the expression: (1+1)
4. Explain Cell lysis by enzymatic method (2)
5. With a neat sketch explain the operation of Disc – stack centrifuge: (1+2)
6. The data given from a particle size analysis of S. cerevisiae cells before and after one
pass through a Gaulin-type high-pressure homogenizer at 8,000 psi indicate a mean
particle size before homogenization of 5.2 micron and a mean particle size after
homogenization of 3.5 micron. After one pass through the homogenizer, only 28% of
the cellular protein is released. How many passes are required to achieve 90% release
of cellular protein? (2)
7. Cyanobacteria are halotolerant. They are capable of accumulating low molecular
weight halides intra cellularly in response to a high osmotic pressure. They can be
cultivated in a medium containing 0.11 M NaCl, or in a medium containing 0.49 M
NaCl and 0.01 M CaCl2. When cells grown in the more saline medium are transferred
to the fresh water, they become permeable: The intracellular carbohydrate and amino
acid are released into the medium within 2 min. Estimate the osmotic pressure
difference which makes the membranes of the cyanobacteria permeable. (2)
8. A tubular-bowl centrifuge is used to concentrate a suspension of geneticallyengineered yeast containing a new recombinant protein. At a speed of 12,000 rpm, the
centrifuge treats 3L broth/min with satisfactory results. It is proposed to use same
centrifuge to separate cell debris from homogenate produced by mechanical
disruption of the yeast. If the average size of the debris is one-third that of the yeast
and the viscosity the homogenate is five times greater than the cell suspension, what
flow rate can be handled if the centrifuge is operated at the same speed? (2)
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9. The centrifugal separation of a biomass of 80m sized cells of density 1.04 g/cc was
carried out in a tubular bowl centrifuge having a dia of 15cm and rotating at 1200
rpm. (1+1+1)
a. Calculate the residence time if the distance between the liquid surface and the
axis of rotation was 0.8cm, the liquid density and the liquid viscosity were 1.0
g/cc and 0.013 g/cm-sec respectively.
b. What would be the volumetric capacity of the centrifuge if its length was
40cm?
c. What will be the time required for centrifuging 1000L of broth?
10. From the profiles (Mechanical disruption of cells vs time), explain the following:
a. Why Alcohol dehydrogenase activity decreases? (1)
b. Why Fumarase activity becomes constant after 30 min? (1)
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