# GATE2018-46

A microbial strain is cultured in a $100$ L stirred fermenter for secondary metabolite production. If the specific rate of oxygen uptake is $0.4 \: h^{-1}$ and the oxygen solubility in the broth is $8$ mg/L, then the volumetric mass transfer coefficient $(K_La)$ (in $s^{-1}$) of oxygen required to achieve a maximum cell concentration of $12$ g/L is (up to two decimal places) ___________

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## Related questions

1
At the end of a batch culture, glucose solution is added at a flow rate of $200 \: ml/h$. If the culture volume after $2$ h of glucose addition is $1000$ ml, the initial culture volume (in ml) is _________
2
An aqueous solution containing $6.8$ mg/L of an antibiotic is extracted with amyl acetate. If the partition coefficient of the antibiotic is $170$ and the ratio of water to solvent is $85$, then the extraction factor is ________
Moist heat sterilization of spores at $121 ^\circ C$ follows first order kinetics as per the expression: $\dfrac{dN}{dt}=-k_dN$ where, $N$ is the number of viable spores, $t$I is the time, $k_d$ is the rate constant and $\dfrac{dN}{dt}$ is the rate of change ... reduce the number of viable spores from an initial value of $10^{10}$ to a final value of $1$ is (up to two decimal places) __________