How to Select Laboratory Reactors
Laboratory reactors are used to grow cells and contain reactions. They are designed for small-scale experiments in fields such as kinetics and yield studies. This product area includes shake flasks, small bioreactors, and other products that can be used to complete a preliminary economic evaluation.
The design of a laboratory reactor affects its processing capabilities. The GlobalSpec SpecSearch database contains products that use these reactor designs.
- Bubble reactors are tall devices which use air alone to mix their contents.
- Airlift reactors are similar to bubble column reactors, but contain a draft tube. Typically, this inner tube improves circulation and oxygen transfer while equalizing shear forces in the reactor.
- Flocculated cell reactors retain cells by allow them to flocculate. They are used mainly in wastewater treatment.
- Fluidized bed reactors use small particles to create a large surface area to which cells can stick. This enables a high rate of oxygen and nutrient transfer to the cells. In fluidized bed reactors, the particles move with the liquid.
- Packed bed reactors do not move with the liquid. They are relatively simple to construct and operate, but can suffer from blockages and poor oxygen transfer.
- Stirred tank reactors use mechanical stirrers with impellers to mix and distribute heat and materials.
In addition to product design, buyers of laboratory reactors need to specify a mode of operation: batch, continuous, and fed-batch. Each mode is described below.
- Batch reactors are simplest type of mode of reactor operation. In this mode, the reactor is filled with medium and the fermentation is allowed to proceed. When the fermentation has finished, the contents are emptied for downstream processing. The reactor is then cleaned, re-filled, re-inoculated and the fermentation process starts again. Batch reactors are less productive than continuous reactors, and must be shut down regularly to minimize the growth rate of bacteria.
- Continuous reactors can immobilize cells. Fresh media is added continuously and bioreactor fluid is removed continuously. Consequently, cells continuously receive fresh medium while waste products and cells are continuously removed for processing. The reactor can thus be operated for long periods of time without having to be shut down.
- Fed-batch reactors are the most commonly type in industry. Fresh med is continuously or periodically added to the bioreactor. Unlike a continuous reactor, however, there is no continuous removal. The fermenter is emptied or partially emptied when the reactor is full, or fermentation is finished. As with the continuous reactor, it is possible to achieve high productivities with fed-batch products. The growth rate of the cells can be optimized by controlling the flow rate of the feed entering the reactor.
Control and Measurement
Laboratory reactors can control the level of dissolved oxygen, the pH level of the sample, the speed of the stirrer, the temperature of its contents, or the amount of foaming that occurs. Severe foaming in a fermentation vessel may cause contamination or loss of material, either of which will decrease yields and invalidate experimental data.
For measurement, laboratory reactors may be equipped with dissolved oxygen sensor, a level sensing system, or an internal temperature sensing element. Depending on the parameters to control and measure, key performance specifications include the number of vessels, the vessel volume, the stirrer speed, and the temperature range.