Preparation of Liquid Medium/broth

The process of growing an organism in the surface of a medium is known as culture. The food source that supports the development of the organism is known as a culture medium. The media for culture are designed so that the organism will receive all the nutrition requirements. However, the media for culture are made in laboratories by weighing and dispensing particular ingredients or by purchasing ready-made media on the market. The majority of the media include organic as well as inorganic nutrients. However, to cultivate a variety of microorganisms, special media are created. If the media is to be solidified required, agar-agar can be mixed with other ingredients. The culture media can be classified into three categories that include semi-synthetic, natural and synthetic media each of which is employed for microbiological studies.

Natural Medium

The natural medium is that which contains the natural products as such, for example diluted blood, urine, milk, vegetable juices, peptone, or animal cells/tissues/organs. In this type of medium, the precise chemical composition is not understood.


Semi-sunthetic Medium

Semi-synthetic media is those where the chemical components are not fully understood, such as like the potato dextrose solution (where the chemical constituents in potatoes aren’t known) Czapek-Dox agar beef extract, nutrient agar media made of agar, etc. The other way around is that media that contain agar are referred to as semi-synthetic mediums. (wi) Synthetic media The type of medium in which chemical compounds that are known to be present to allow the isolation of numerous microorganisms is known as synthetic medium. The synthetic medium is diverse in nature, for example;

  1. General purpose medium (for routine microbiological work),
  2. Differential medium (to differentiate the groups of microorganisms by opting such media that contain dyes and colour indicators to give biochemical response .g. MacConkey and Eosine methylene blue agar),
  3. Selective medium (contains compounds found in differential media and certain agents that further inhibit growth of most of the microorganisms and promote growth of the required ones), 
  4. One-purpose medium (highly selective medium used to isolate specific microorganisms, for example, brilliant green agar for isolation of Salmonella from faces) or
  5. Assay medium (to assay antibiotics. amino acid, vitamins, etc.).

Preparation of Liquid Medium/broth

As opposed to fungi and bacteria which are usually cultivated within broths, i.e. the broth is devoid of Agar. The need for nutrients can be fulfilled by supplementing beef extract ( that is a source of minerals salts nutrients, organic carbon and nitrogen etc.).) as well as peptone (which is a semi-digested form of protein). Methods of preparation of nutritional broth is described below:



  • Nutrient broth medium*
  • HCL 1N
  • NaOH 1N
  • pH meter
  • Distilled water
  • Autoclave
  • Heater
  • Culture tubes
  • Glass rod
  • Beaker (1 I capacity)
  • Measuring cylinder

Nutrient broth medium Composition

Peptone0.5 g
Beef extract3.0 g
Distilled water1lit

PH – 7.0

Procedure for the Preparation of Liquid Medium

  1. Be sure to accurately weigh the chemical components of the broth that contains nutrients and place them in the beaker that holds 500ml distillate water.
  2. Begin to heat the contents gently by stirring lightly to dislodge the ingredients.
  3. You can add more distillation water to increase 1 litre of volume.
  4. Determine the your broth’s pH using a pH meter . Then, alter your pH until 7.0 with the addition of drops either NaH or HC1 solution.
  5. Pour 10 ml of broth into each of the culture tubes.
  6. Make the cotton plugs (as explained in Experiment No. 2.2) and then place them to the mouths of the broth tubes.
  7. Close the opening of cotton plugs with aluminum foil or paper and secure with thread or rubber bands.
  8. Transfer all broth tubes to an iron stand for test tubes or iron container.
  9. Place the basket in the pressure cooker/autoclave and sterilize at 121°C for 30 mins.
  10. Once the temperature is cool, you can get the broth tubes out.
  11. Use the broth tube as is required, or store it at room temperature to allow for later use.

A few things to consider when making the media

  • Ready-made or dehydrated media is available on the market. These are commercial preparations that are utilized following the weighing (specific measurement) and then dissolving in the needed amount of distilled water.
  • The instructions for preparation are usually mentioned in the labels of the container. It is important to accurately weigh them and prepare them in accordance with the instructions in the instructions on the container.
  • You can make a smaller quantities in media (less than 1 Liter). If 100 ml of medium is needed, just divide the water and the medium by 10. It is simple to determine the amount of powdered media to distilled water , and apply the appropriate amount when preparing the media.
  • The agar should be dissolved in hot water prior to mix with the other chemical.
  • In the event that the use of different chemicals is required to make media and its preparation, the use of a magnetic stirrers that have Teflon coat magnet assists in the dissolution of the chemical.


  • A Simple Preparation of Liquid Media for the Cultivation of Strict Anaerobes, Yoshihito Uchino* and Suzuki Ken-Ichiro
  • A Simple and Easy Method for Preparing Solid and Liquid Media for Plant Culture, Noor Illi Mohamad Puad and Tang Chi Wai,

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