Laboratory Incubator: Principle, Parts, Types, and Uses 

A laboratory incubator is an equipment that provides a controlled environment for the growth of microorganisms. Whereas incubation is the process of providing a controlled environment.

Principle of Laboratory Incubator

The basic principle of a laboratory incubator depends on the thermo-electricity principle, i.e., heat or thermal energy converts into electrical energy. The thermostat in the incubator maintains a constant temperature by creating a thermal gradient. Thus, the formed thermal gradient generates a thermoelectric effect which is a voltage. 

A predetermined temperature is set in the instrument because different microorganisms require different temperatures for growth. For example, the suitable incubation temperature for mesophilic bacteria is 37℃, whereas for molds and yeast, it is 28℃. The temperature inside the incubator increases when power is supplied. The temperature control depends on the temperature sensor, controller, and contractor. 

Once the power is supplied to the incubator, the contractor is energized, which powers the bulbs. The bulbs are the heating element of the incubator, and fans ensure equal hot air distribution in the incubator. When the incubator reaches the desired temperature, the contractor is de-energized, temporarily shutting off the power supply. A thermometer displays the temperature inside the instrument. 

Parts of Laboratory Incubator

The laboratory incubatory has the following parts:

Cabinet with Door

The cabinet of the incubator is double-walled. The inside of the cabinet is made up of aluminum, whereas the outside is made up of stainless steel. The glass wool insulates the gap between the double-wall to prevent heat loss. The storage capacity of the cabinet ranges from 20 liters to 800 liters.

The door is present at the front part of the incubator. The door has glass for visualizing the contents present inside the cabinet. Asbestos door gaskets provide air tight seal between the door and the cabinet. The gaskets prevent hot air from escaping outside the cabinet and non-sterile air from entering the cabinet. 

Note: Unlike a hot air oven there is glass for visualizing contents in the incubator. 

Control panel

The control panel is outside the cabinet and has many switches to control different parameters of the incubator. It also controls the thermostat.

Thermostat

The thermostat provides the desired temperature and maintains the temperature during heating and non-heating cycles. 

Thermometer

The thermometer is in the top part of the outer wall of the cabinet. One end of the thermometer has gradations indicating the temperature, and another has a mercury bulb embedded inside the incubator. 

Shelves

The shelves are present in the inner part of the incubator. These are removable, which makes their cleaning easy. The shelves hold the Petri plates containing culture media. Perforations on the shelves help circulate hot air throughout the incubatory.

Additional parts

Some incubator has HEPA filters which creates a closed-loop system to reduce the chances of contamination. Similarly, some incubators have humidity and CO₂ control to provide the desired environment for some microorganisms’ growth.

Types of Laboratory Incubator

Based on their size and purpose, the laboratory incubator is of the following types:

Cooled/Refrigerated Incubator

The cooled or refrigerated incubator has a refrigeration system in them. These provide temperatures below the ambient temperature. The cooled incubators offer precise temperature control and have air circulation fans that provide fresh air inside the chamber. It also has different sensors which monitor the temperature. These are used in biology and microbiology laboratory.

BOD (Biological Oxygen Demand) Incubator

BOD incubators are used to grow yeast and mold in the laboratory. It provides a temperature of 20-25˚C, also known as a low-temperature incubator.

Humidity Incubator

A humidity incubator is a special type of incubator with control settings for humidity. It is important because the growth of certain organisms requires some moisture. Temperature and humidity are controlled simultaneously. Indirect heating helps in maintaining the special atmosphere inside the cabinet.

CO₂ (Carbon Dioxide) Incubator

Some microorganisms cannot grow in oxygen reach environment.CO₂ incubator provides this environment. It has a special mechanism that helps maintain the CO₂ inside the chamber of the incubator. Commonly infrared or thermal conductivity sensors hold the CO₂ level. It also has a water tray for maintaining humidity levels. The incubator mimics the condition of the human body that makes it susceptible to contamination. Therefore, there is a special sterilization system that cleans the incubation chamber and prevents any contamination. 

Shaking Incubator

A combined form of motor/shaker and incubator is termed a shaking incubator. The incubator provides controlled temperature, humidity, oxygen level, etc. It also offers constant shaking for a homogenous mixture of the samples like a centrifuge. It is mainly used in molecular biology and genetics. 

Benchtop/Standard Incubator

Benchtop/standard incubators are the incubator present in the most common laboratory. The temperature ranges from ambient to up to 100℃. Most of these incubators have a glass door, alarms, and a display screen that displays the temperature and time. 

Uses of Laboratory Incubator

The incubator has a wide range of use. Some of the applications are as follows:

• In microbiology laboratories, an incubator helps to grow bacteria, fungi, and other microorganisms. 
• Similarly, it helps in growing viruses in the cell cultures.
• Likewise, in zoology laboratories incubator provides the environment for hatching the eggs of insects, birds, and other oviparous organisms.
• It also helps to store biological specimens before analysis in medical laboratories.

Precautions

While operating the incubator, you should follow the following precautionary measure:

• Avoid opening the door of the incubator unnecessarily.
• Also, maintain the temperature of the incubator carefully.
• Clean the incubator regularly.
• If incubation of Petri plates is done for a longer time, the Petri plates should be placed in a moist chamber with damp sterile cotton wool at the bottom.
• Similarly, for the incubation of test tubes for a long time and at a higher temperature, push a cotton plug inside the neck of the tube to prevent drying of the medium. 

References

• Global Lab Supply. (2020). Different Types Of Incubators In Laboratories. Fuzia.com. Retrieved 13 June 2022, from https://www.fuzia.com/article_detail/131535/different-types-of-incubators-in-laboratories.
• Incubator: Introduction, Principle, Types, Uses and Keynotes. Retrieved 13 June 2022, from https://universe84a.com/incubator/.
• Laboratory Incubators. BioCompare. Retrieved 13 June 2022, from https://www.biocompare.com/Lab-Equipment/6736-Laboratory-Incubators/.
• Manandhar, S., & Sharma, S. (2017). Practical Approach to Microbiology (3rd ed., pp. 14-15). National Book Centre.