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Mid-Sem Examination (Sep 2021)
Biochemical Engineering (BT 303)
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Total Marks: 30
Answer All the Questions
Assumptions Made Should be Justified Appropriately
Ambiguous Answers Will NOT be Evaluated
1. Calculate the missing data in the following table:
Element
%
in Theoretical
Substrate
% element in Substrate for
cell
yield
substrate
1 g cells
weight
(g cells/
g element)
C
45
Glucose
O
30
Air
N
12
NH4Cl
H
7
c)
P
3
KH2PO4
S
1
MgSO4.7H2O
K
1
KH2PO4
Mg
0.5
MgSO4.7H2O
a) Assumes no acetate formation and aerobic growth with glucose as carbon- and energy
source. About 50% of the glucose is used as carbon source and an approximately equal
amount is used for energy production.
b) The cell oxygen is mainly derived from the organic carbon source. The oxygen that is
provided by aeration is mainly used for respiration.
c) Hydrogen is provided by water and from organic compounds.
d) Mol.wt: NH4Cl (53.5); KH2PO4 (136); K (39.1); P (31); MgSO47H2O (246.5);Mg (24.3)
(10 Marks)
2. Yeast (C6H10O3N) grown on glucose is described by the stoichiometric equation as given
below:
+ 0.48
+3
→ 0.48
+ 3.12
+ 4.32
Calculate the following for a design requiring 50 g/L of yeast in a batch reactor of 100,000
liters.
(a) Nutrient media concentration for glucose and ammonium sulfate.
(b) Calculate YX/S and YX/O2
(c) Calculate total oxygen required
(d) Determine oxygen uptake rate (g O2 L-1 h-1) when cell concentration increases at a rate
of 0.7 g L-1 h-1
(5 Marks)
(Continued in next page)
3. In order to facilitate multiple elemental balance calculations, the formulae of chemical
compounds are often written in C-molar notation. Their most important properties are the
C-molar molar mass, M’i and their C-molar degree of reduction, . In order to familiarize
yourself with these concepts, complete the following table:
Si.No
Compound
Molecular
C-Molar
M’i
Formulae
Formulae g/C-mol
1.
Glucose
2.
Lactose
3.
Ethanol
4.
Methanol
5.
Acetic acid
6.
Lactic acid
7.
Carbon dioxide
8.
Methane
9.
Ammonia
10.
Water
11.
Oxygen
12.
Yeast
(5 Marks)
4. During the growth of E. coli in a batch reactor, the cell growth kinetics can be modelled
using the Monod’s model. At the start of the exponential growth, the concentration of cells
is 0.08 g/L and the substrate concentration is 36 g/L respectively. Find the time where
maximum population of cells is reached given that µmax = 0.55 h-1, KS = 1.2 g/L and specific
substrate consumption rate ( q S ) = 1.4 (g Substrate)/(g cells)(h).
(10 Marks)
---------------------------------------Wishing You All the Best-----------------------------------------