The Basic System in a Fed-Batch Reactor

To avoid massive dilution of the reaction mixture in the fed-batch reactor, the initial reactor volume was rather large relative to the flow rate of the feed streams. However, the initial volume of the reactor affects the amounts of enzymes that are required. As shown in Section 4.1.4.1, large amounts of enzymes are needed for each volume unit in the reactor, and in order to work with reasonable amounts of enzymes, this volume was limited to 50 mL. 

The initial volume of 50 mL chosen for the fed-batch reactor imposes relatively low flow rates for the feed stream, as indicated above. However, variations in the concentrations of the substrates in the feed stream are based on variations in the flow rates, and these should be accurate. These considerations lead to a need for accurate changes in a limited range of flow rates. The flow rate of 7 mL/h is in the lowest range of the rates defined by the producer for the peristaltic pumps used, so in the settings defined by the producer, accurate variations could not be obtained. Thus, the peristaltic pumps were operated with tubings of very small diameter. These tubings, of 0.5 mm inner 

Delineation of the operational parameters was achieved using computer simulations as described in Section 4.1.3.1. The values of K j (determined experimentally), the initial reactor volume, and the initial concentration of NADP were fed into the program. Employing the conclusions obtained from the theoretical simulations, the other parameters (i.e., flow rates, concentration range of the substrates, and Vmj values) were calculated according to the output signal desired. 

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Figure 4.58 Experimental configuration employed for operation of the basic system in a fed-batch reactor. (.) control lines (----) ...

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