Microbiological incubator

An incubator usually has a chamber volume of between 20 and 800 litres and a temperature range from +5 °C above room temperature to +100 °C, even though breeding temperatures usually do not exceed  40°C (details on the basic operation and features of a temperature control chamber). As a rule, natural convection is sufficient in microbiology incubators. When fully loaded, however, a forced air circulation can support temperature distribution inside the chamber (for details on heating, natural convection and forced air circulation, see 1.3.1.).

Since hygiene is extremely important when working with living organisms, some manufacturers offer the option of sterilising the interior in the incubator (see Hygiene and Avoiding Contamination).

 

Special case: Cooled incubators

Normal temperatures in a microbiological incubator lie at around the same temperature as the human body (37 °C). For applications that require temperatures in the range of room temperature and below down to sub-zero temperatues, or if the ambient temperature is very high, special cooled incubators are the products of choice. In food biology, the cooled incubator is used, for example, for shelf-life tests and for storage purposes, in agricultural science for soil germination, in environmental technology for determining the biochemical oxygen demand, in biology for cultivating model organisms such as threadworms or fruit flies and for the cultivation of fungi or yeast, and in protein biology for growing crystals. Equipped with additional lighting (day-night rhythm), the cooled incubator is ideal for growing plants in zoology.

cooled incubator with compressor and inner glass door

Cooled incubator with compressor and inner glass door

 
 

Compressor cooling in the cooled incubator

In practice, the interior in the cooled incubator is mainly cooled by means of a compressor, as is found in conventional refrigerators. In order to prevent so-called cold spots, and thus the drying out of samples, some manufacturers separate the components of the cooling system from the interior with a cooled air jacket (see condensation).

Peltier cooling in the cooled incubator

Some manufacturers offer cooled incubators that are heated and cooled by means of Peltier technology. If a Peltier element is energised, one side is cooled and the opposite side simultaneously heats up. Simply by reversing the polarity of the supply voltage, the hot and cold sides of the Peltier element can be swapped. The advantages of Peltier technology lie in a low energy consumption in partial load operation, a low noise level and high control precision. Since cooled incubators with Peltier elements work almost without any vibration, they are particularly suitable for protein crystallography and breeding insects.

 

Overview Glossary Temperature control chamber

 


Picture credit: Memmert GmbH + Co. KG

Heating and cooling a cooled incubator by means of Peltier-technology
 
Air jackets around the interior of a cooled incubator prevent samples from drying out