Batch experiments evaluated using different rate-limiting substrates (glucose an

Question

Batch experiments evaluated using different rate-limiting substrates (glucose and acetate) showed a
mass doubling time of 2.4 h for Pseudomonas sp., whether acetate or glucose was rate-limiting. And,
cell yields on these substrates were determined to be 0.50 g cell/g substrate in each case. Monod
kinetics were generally followed in each case as well, with KS = 1.3 g/L when acetate was limiting
and KS = 0.70 g/L when glucose was limiting. However, the batch data also showed that glucose
inhibits cell growth such that ? = (?max.S)/(KS + S + S2/KI), where KI = 22 g/L.
Consider the growth of Pseudomonas in a 750 L chemostat with a 500 L working volume operating at
steady state. Glucose and acetate are each present in the nutrient feed to the bioreactor, at S0,glu = 10
g/L and S0,acet = 4.8 g/L.
a. At what nutrient flow rate (L/h) will “washout” occur?
b. With inlet nutrient concentrations as specified above, suppose we have substrate conversions of
84% for glucose and 76% for acetate. Determine the cell productivity (g/L.h).
c. Suppose continuous operation is accompanied by mass transfer limitations (which were not an
issue in the batch experiments). Briefly explain whether you would expect the washout flow rate
to decrease, increase, or remain the same compared to that determined in part (a).

Explanation / Answer

Batch experiments evaluated using different rate-limiting substrates (glucose an

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