Biocatalysis Reactors

Immobilized enzymes are usually used in one of three reactors: fluidized bed, packed bed and batch reactor. When considering the pharmaceutical industry, the steel batch reactors are the industry standard. Compared to the other reactors, this small batch reactor is less expensive and is ideal for only a few cubic meters. Equipped with a stainless steel filter, the immobilized enzyme can be removed after each cycle.The are three types of reactors when considering the immobilized enzyme process, these are (from left to right):

  • Fluidized reactor

  • Packed bed reactor

  • Rotating bed reactor

Fluidized Reactor
A fluidized bed reactor (FBR) or expanded bed reactor, is a type of reactor device that can be used to carry out multiphase chemical reactions. 

They consist of a bed of immobilized enzyme which is fluidised by the rapid upwards flow of the substrate stream alone or in combination with a gas or secondary liquid stream, either of which may be inert or contain material relevant to the reaction.

To overcome fouling, pressure drop can be minimized with the use of an expanded bed reactor operated in up-flow mode. However, residence times dictated by the reduced flow may result in low conversion yields.

Packed Bed Reactor
The most common enzymatic reactor for continuous operation is a packed-bed setup. These reactors are tubular and are filled with immobilized enzyme particles. The chemical reaction takes place on the surface of this catalyst. 

Continuous operation results in very high productivity, but high pressures can be generated, leading to fouling of the immobilized enzyme upon use.

Rotating Bed Reactor
Smaller-scale bioconversions are typically carried out in stirred tanks, which are cost-effective and simple to operate. Due to high acceleration forces upon the fluids, thinner mass transfer films are formed, leading to higher rates of mass transfer.

However, shear stress induced by stirring can create a hazardous environment for immobilized biocatalysts, as they are prone to abrasion in this reactor.