GasPak Anaerobic System: Principle and Application

GasPak anaerobic system is used to create an oxygen-free environment for the growth of anaerobic microorganisms. At present, it is the most commonly used method for anaerobiosis. It is very simple to perform and is perfect for a laboratory having less sample load.

Components of GasPak Anaerobic System

  1. polycarbonate jar (or anaerobic container)
  2. a lid with a gasket to prevent airflow (for jar system)
  3. Indicator strip (a strip impregnated with an oxidation-reduction indicator such as methylene blue or resazurin)
  4. disposable gas generating pouch (a pouch containing sodium borohydride and sodium bicarbonate)
  5. a palladium catalyst

Principle

Inoculated plates or tubes are placed inside the polycarbonate jar or anaerobic container along with gas generator sachet and indicator strip and is sealed completely. In the presence of water, chemicals present inside the sachet i.e. sodium bicarbonate (NaHCO3) and sodium borohydride (NaBH4) react chemically producing hydrogen and carbon dioxide gas.

GasPak Anaerobic system
Anaerobic Jar: GasPak system

The hydrogen thus produced reacts with oxygen present inside the jar producing water (which forms as condensation on the inside of the jar).

2H2 + O₂ + catalyst = 2H2O

This reaction is catalyzed by the element palladium, which is attached to the underside of the lid of the jar. The carbon dioxide replaces the removed oxygen, creating a completely anaerobic environment.

Note: Current anaerobic gas-generating systems do not require a catalyst and/or the addition of water to activate these systems. Please refer to the user manual provided by the supplier before commencing your works.

Steps

  1. Inoculate agar plate with test strain.
  2. Place inoculated agar plates in an anaerobic jar, container or pouch.
  3. Add anaerobic indicator strip.
  4. Add the required number of gas generator sachet after opening the sealed GasPak container and place the lid in place or seal the pouch/container.
  5. Incubate at the desired temperature.
  6. Check anaerobic indicator strip for color change.

Note: These steps may slightly vary based on commercial suppliers. Please refer to the user manual provided by the supplier.

Indicator of anaerobiosis

The effectiveness of GasPak anaerobic system can be checked by the following methods:

  1. Anaerobic indicator strips:
    1. Impregnated with methylene blue: remains colorless in anaerobic conditions, but turns blue on exposure to oxygen.
    2. Impregnated with resazurin, a redox indicator: colorless (white) in anaerobic condition but turns to pink in the presence of oxygen.
  2. Biological indicator: Plate inoculated with Pseudomonas is incubated along with other inoculated plates for anaerobic cultures. The absence of growth of Pseudomonas (which is an obligate aerobe) indicates that perfect anaerobiosis has been achieved.

Commercial products

BD GasPak System
BD GasPak System

BD GasPak EZ gas generating system is the first complete, waterless and catalyst-free system that produces anaerobic, microaerophilic or carbon dioxide enriched environment. This fully integrated system is easy to use and is available on two systems; container system & pouch system. BD container system is available in 10, 15 and 30 Petri dish capacity. Pouch system is available in 1-4 petri dish capacity with all needed materials (pouches, sachets, and indicators).

References and further reading

About Acharya Tankeshwar 444 Articles
Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. I am working as an Asst. Professor and Microbiologist at Department of Microbiology and Immunology, Patan Academy of Health Sciences, Nepal. If you want me to write about any posts that you found confusing/difficult, please mention in the comments below.

2 Comments

  1. Hello. Clarify me if I can state the following:
    if using GasPak anaerobic system and after incubation period, colonies are observed, then, presence of strict anaerobes should be discarded?
    Thank you.

    • Hello Lynette Diaz,
      No, you can not state that.
      If anaerobiosis is achieved (as shown by the change in the color of the indicator) observing colonies means presence of anaerobes.

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