PFF with Cell Recycling

The cell concentrations of the outlet stream, can be estimated from the overall cell balance 

The analysis in this section and the next can be also applied for a cell settler as a cell separator. The outlet stream of the cell settler will be equal to F = B + L and its concentration will be (B/F)CXy = /5CSf. 

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A PFF requires the initial presence of microorganisms in the inlet stream as a batch fermenter requires initial inoculum. The most economical way to provide cells in the inlet stream is to recycle the part of the outlet stream back to the inlet with or without a cell separation device. Figure 6.17 shows the schematic diagram of a PFF with cell recycling. Unlike the CSTF, the PFF does not require the cell separator in order to recycle, though its presence increases the productivity of the fermenter slightly as will be shown later. The performance equation of the PFF with Monod kintics can be written as ... 

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