Question

Zymomonas mobilis is used to convert glucose to ethanol in a batch fermenter under anaerobic conditions. The yield of biomass from substrate is 0.06 g g^-1; YPX is 7.7 g g^-1. The maintenance coefficient is 2.2 g g^-1 h^-1; the specific rate of product formation due to maintenance is 1.1 h^-1. The maximum specific growth rate of Z. mobilis is approximately 0.3 h^-1.5 g bacteria are inoculated into 50 litres of medium containing 12 g l^-1 glucose. Determine batch culture times required to produce 10 g biomass.

(a) 3.1 h

(b) 3.3 h

(c) 3.5 h

(d) 3.7 h

I had been asked this question by my school principal while I was bunking the class.

The question is from Ideal Reactor Operation in portion Reactor Engineering of Bioprocess Engineering

Answer 1

Right option is (d) 3.7 h

To elaborate: Yxs = 0.06 gg^-l; Ypx= 7. 7 gg^-l; μmax = 0. 3 h^-l; ms=2.2 gg^-l h^-l; mp= 1.1 h^-l; x0=5g/501= 0.1 gl^-l;s0= 12 gl^-l.

If 10 g biomass are produced by reaction, the final amount of biomass present is (10 + 5) g = 15 g. Therefore xf = 15 g / 50 l = 0.3 g l^-1.