Problem 1. A fermentation process involving a single stage chemostat is used to

Question

Problem 1.

A fermentation process involving a single stage chemostat is used to produce the amino acid lysine. The same process has been modified to include cell recycle, with a recycle ratio of 0.3 and a cell concentration factor of 2.5. Assuming that all other conditions are identical, how much will cell concentration change due to the use of cell recycle?

Problem 2.

A two-stage fermentation process is being used to grow fungal cells. The feed stream is at a flowrate of 50 L/min and contains 220 g/l Glucose (which is the limiting nutrient). The volume of the first fermenter is 400 L. The steady state cell concentration in fermenter 1 is 110 g/l, and the steady state cell concentration in fermenter 2 is 140 g/l. Other known fermentation parameters are Yx/s=0.65, µ2=0.04 min-1.

Determine the following: a) µ1, b) Volume of fermenter 2, c) Steady-state substrate concentrations in fermenter 1 and fermenter 2.

Problem 3.

A fermentation process is being used to produce yeast cells. Using the following conditions, determine Productivity for both batch and continuous fermentation processes at growth rates of µ = 0.05, 0.1, 0.2, 0.4, 0.8, and 1 hr-1. Assume that the continuous system is a standard single stage continuous reactor with no recycle. Xo = 2.0 g/l, Xf =3.5 g/l Total batch turnaround time, t = 1.5 hrs (includes lag, delay, and turnaround times).

Make a graph of Productivity vs Growth Rate comparing both systems.

What conclusions can be made regarding productivity in batch and continuous systems as a function of growth rate?

Explanation / Answer

A chemostat setup consists of sterile fresh nutrient reservoir connected to a growth chamber, which is also called reactor. Fresh medium that contains all the essential cell nutrients is pumped continuously to the chamber.Varying the concentration of this growth limiting nutrient will change the steady state concentration of cells. Another way of controlling the steady state cell concentration is manipulating the flow rate of the medium. Temperature and pressure must be controlled to maintain optimum conditions for cell growth. Based on the initial concentrations and certain other parameters, the cell concentration and the yield percentage will be standard. If this chemostat is modified to include cell recycle maintaining all other conditions the same, then the yield would be bit higher.

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