Question

Which of the following does not affect KLa value?

(a) Air flow rate

(b) Presence of enzymes

(c) Presence of antifoam agents

(d) Degree of agitation

This question was addressed to me in class test.

This is a very interesting question from Measurement of KLa in portion Mass Transfer of Bioprocess Engineering

Answer 1

Correct choice is (b) Presence of enzymes

To elaborate: The mass transfer coefficient is strongly affected by agitation speed and air flow rate. The mass transfer coefficient increases with agitation speed and air flow rate. Since fermentation is usually conducted at constant temperature and pressure so thermodynamically antifoam agents make the foam unstable causing ΔG < va ΔA (where ΔG is the free energy change, va is the surface tension and ΔA is the change in area).