GATE 2025 BT – Question 62
A 2 L bioreactor is being operated as a chemostat, at a flow rate of 0.8 L/h and sterile feed of 10 g/L substrate. The bacterial growth follows Monod kinetics at a maximum specific growth rate of 0.6 h$^{-1}$ with a Monod constant of 0.5 g/L and a biomass yield coefficient of 0.4 g/g.
The exit biomass concentration is _______ g/L. (Round off to one decimal place)
Practise this question in The GATE Grind →
Show answer and explanation
Correct answer: 3.58 to 3.62
Explanation
The dilution rate is $D = \frac{0.8}{2} = 0.4$ h$^{-1}$. At steady state $\mu = D$, so $0.6\frac{S}{0.5 + S} = 0.4$, which gives $S = 1$ g/L. The biomass is $X = Y(S_0 - S) = 0.4 \times (10 - 1) = 3.6$ g/L.