Enzyme catalyzed reactions are rapidly becoming an invaluable tool for the synthesis of many active pharmaceutical ingredients. These reactions are commonly performed in batch, but continuous biocatalysis is gaining interest in industry because it would allow seamless integration of chemical and enzymatic reaction steps. However, because this is an emerging field, little attention has been paid towards the suitability of different reactor types for continuous biocatalytic reactions. Two types of continuous flow reactor are possible: continuous stirred tank and continuous plug-flow. These reactor types differ in a number of ways, but in this contribution, we focus on residence time distribution and how enzyme kinetics are affected by the unique mass balance of each reactor. For the first time, we present a tool to facilitate reactor selection for continuous biocatalytic production of pharmaceuticals. From this analysis, it was found that plug-flow reactors should generally be the system of choice. However, there are particular cases where they may need to be coupled with a continuous stirred tank reactor or replaced entirely by a series of continuous stirred tank reactors, which can approximate plug-flow behavior. This systematic approach should accelerate the implementation of biocatalysis for continuous pharmaceutical production.Catalysts 2019, 9, 262 2 of 17 counterparts) and thereby the use of flow technology is hard to justify. In reality, the arguments for flow technology are perhaps a little different for enzymes and, in this brief review, we will discuss the issue of reactor selection, in order to capitalize upon the benefits of both flow technology and biocatalysis. Downstream unit operations are not included in this discussion. Figure 1 shows schematic diagrams of the three ideal reactor types, namely the batch stirred tank reactor (BSTR), the continuous stirred tank reactor (CSTR) and the continuous plug-flow reactor (CPFR). The characteristics of these reactors have been described in extensive detail elsewhere [18] and will therefore be only briefly summarized here.
Reactor TypesCatalysts 2019, 9, x FOR PEER REVIEW 2 of 17 (compared to their chemical counterparts) and thereby the use of flow technology is hard to justify. In reality, the arguments for flow technology are perhaps a little different for enzymes and, in this brief review, we will discuss the issue of reactor selection, in order to capitalize upon the benefits of both flow technology and biocatalysis. Downstream unit operations are not included in this discussion.
Reactor Types