Questions and Answers

During bioconversion of sucrose to citric acid by Aspergillus niger, final samples of 6 batches of fermentation broth were analyzed for citric acid content. The results (in g L⁻¹) were found to be 47.3, 52.2, 49.2, 52.4, 49.1 and 46.3.

Q54 The mean value of acid concentration will be
A 49.4
B 51.0
C 48.2
D 50.8

Q55 The standard deviation for the above results is
A 2.49
B 3.0
C 1.84
D 5.91

The standard redox potential values for two half‐reactions are given below. The value for Faraday’s constant is 96.48 kJ V⁻¹ mol⁻¹ and gas constant R is 8.31 J K⁻¹ mol⁻¹.
NAD⁺ + H⁺ + 2 e⁻ ⇌ NADH –0.315 V
FAD + 2 H⁺ + 2 e⁻ ⇌ FADH₂ –0.219 V

Q52 The ΔG°′ for the oxidation of NADH by FAD is
A –9.25 kJ mol⁻¹
B –103.04 kJ mol⁻¹
C +51.52 kJ mol⁻¹
D –18.5 kJ mol⁻¹

Q53 The value of ΔG′, given Keq as 1.7 at 25 °C, will be
A –17.19 kJ mol⁻¹
B –19.8 kJ mol⁻¹
C +52.82 kJ mol⁻¹
D –117.07 kJ mol⁻¹

The width of the lipid bilayer membrane is 30 Å. It is permeated by a protein which is a right‐handed α‐helix.

Q50 The number of α-helical turns permeating the membrane is
A 5.6 turns
B 3.5 turns
C 6.5 turns
D 5.0 turns

Q51 The number of amino acid residues present in the protein is
A 15
B 18
C 17
D 20

A culture of Rhizobium is grown in a chemostat (100 m³ bioreactor). The feed contains 12 g L⁻¹ sucrose, Ks for the organism is 0.2 g L⁻¹ and μₘ = 0.3 h⁻¹.

The flow rate required to result in steady‐state concentration of sucrose as 1.5 g L⁻¹ in the bioreactor will be
A 15 m³ h⁻¹
B 26 m³ h⁻¹
C 2.6 m³ h⁻¹
D 150 m³ h⁻¹

If Yₓ/ₛ = 0.4 g g⁻¹ for the above culture and steady‐state cell concentration in the bioreactor is 4 g L⁻¹, the resulting substrate concentration will be
A 2 g L⁻¹
B 8 g L⁻¹
C 4 g L⁻¹
D 6 g L⁻¹