4) Bacillus is cultivated in a 20 m3 fermenter at 30C for the production of a bioinsecticide. The kLa is determined by the dynamic method. The air flow is turned off and the dissolved O2 concentration drops. After a period the air is turned back on. When steady state is reached, the percentage of dissolved oxygen saturation is 78%. The following results were obtained:

Time (s) CL (%) of saturation 5 50 15 66

a) Estimate the value of kLa

b) Suppose there was a failure in the measurement of the percentage of oxygen saturation, which instead of 78% was measured 70%. What would be the error in determining kLa?

Answer of a and b a) kLa=0.084 s-1

b) new kLa=0.16 s-1 , 90% error