Question

Refer to Q8 and, calculate the bacteria suffer growth inhibition after copper sulphate is accidently added to the fermentation broth. This causes a reduction in oxygen uptake rate to 3 mmol g^-1 h^-1. What maximum cell concentration can now be supported by the fermenter?

(a) 50 gl^-1

(b) 10 gl^-1

(c) 25 gl^-1

(d) 55 gl^-1

The question was asked during an interview.

Enquiry is from Oxygen Uptake in Cell Cultures in chapter Mass Transfer of Bioprocess Engineering

Answer 1

Right answer is (a) 50 gl^-1

Explanation: Assume that addition of copper sulphate does not affect C*AL or kLa. If qo is reduced by a factor of 12.5/3 = 4.167, xmax is increased to:

xmax = 4.167 (12 gl^-1) = 50 gl^-1

To achieve the calculated cell densities all other conditions must be favourable, e.g. sufficient substrate and time must be provided.