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Peptone Water Composition, Preparation, Uses, Principle

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Peptone Water is a type of broth medium. This media is mainly used to grow the organism and is also used as a base for determining carbohydrate fermentation patterns of non-fastidious organisms. It is also used to detect indole production by the organism.

Peptone water is a type of nutrient broth used in microbiological culture media. It is made by hydrolyzing animal protein sources, such as meat or casein, with proteolytic enzymes to produce a mixture of peptides and amino acids. Peptone water is used to support the growth of a wide variety of microorganisms, including bacteria, yeasts, and fungi. It is often used as a base for preparing other types of culture media or as a rinse solution for microbial samples. Peptone water can be sterilized by autoclaving or other methods to eliminate any contaminants before it is used in a laboratory setting.

Principle of Peptone Water

Peptone and sodium chloride water are its two main ingredients. Peptone is a source of many vital nutrients, including nitrogenous and carbonaceous substances, long-chain amino acids, and vitamins. Sodium chloride serves as both an electrolyte and a regulator of the medium’s osmotic pressure.


Used as a substrate, it is ideal for learning about indole synthesis. Peptone Water’s usage of tryptophan-rich peptone facilitates indole detection with either the Kovacs or the Ehlrich reagent. Sugar and markers like bromocresol purple, phenol red, or bromothymol blue are added to Peptone Water to conduct investigations on carbohydrate fermentation. Researching an organism’s fermentation of a narrow carbohydrate range can help biologists distinguish between species. The inclusion of a phenol red indicator, which causes the medium to turn from red to yellow in acidic circumstances, can be used to identify the acidity created during fermentation. The Durhams tube is placed in the medium to detect gas generation if it is created by the organism.

Composition of Peptone Water

IngredientsGms / L
Sodium chloride5.0

Final pH should be (at 25°C) 7.2±0.2

Preparation of Peptone Water

  1. Dissolve 15 grammes in 1 litre of distilled water.
  2. Reconcile everything, then put everything in the appropriate containers.
  3. Make sure everything is sterile by autoclaving it at 121 degrees Fahrenheit and 15 pounds of pressure for 15 minutes.

Requirements for The test with Peptone Water

  • Peptone-water
  • inoculation loop or dropper as a test specimen
  • Controlled strains ( Staphylococcus aureus ATCC V25923, Escherichia coli ATCC 25922, and uninoculated medium)
  • Bunsen burner
  • Incubator
  • Garbage can

Procedure of Peptone Water

  1. Warm the medium to 37°C (or room temperature) before inoculating.
  2. Prepare an inoculum and inoculate the specimen/test organism.
  3. 24 hours of aerobic incubation at 35–37 degrees ( or depending on the nature of suspected organisms).
  4. Look for signs of turbidity.

Result Interpretation on Peptone Water

Cultural characteristics observed after an incubation at 35-37°C for 18-24 hours

OrganismTest Result
Staphylococcus aureusnegative reaction, no red ring at the interface of the medium on addition of Kovac’s reagent
Escherichia colipositive reaction, red ring at the interface of the medium on addition of Kovac’s reagent
Salmonella Typhimuriumnegative reaction, no red ring at the interface of the medium on addition of Kovac’s reagent

Storage and Shelf life of Peptone Water

  • Keep in a cool, dark place between 2 and 8 degrees Celsius.
  • If there are any visible symptoms of damage (discoloration, contamination), the media should not be used (turbidity).
  • Because of its sensitivity to light and heat, the product can prevent damage from sun exposure, steam, dampness, and even frost.

Uses of Peptone Water

  • Peptone water is the most basic medium, and it’s utilised as a growth medium and a basis for carbohydrate fermentation media.
  • Since it is a liquid, it can be used to detect indole.
  • For the study of carbohydrate fermentation patterns in non-fastidious organisms, this minimal growth media is employed (E. coli. Klebsiella, Proteus, etc).
  • It can be used in a variety of microbial enumeration, sensitivity, and motility tests, as well as as a diluent for suspension preparation of non-fastidious organisms.
  • Vibrio cholerae can be grown and enriched in water with a peptone conversion at a pH of 8.4. (etiological agent of cholera).
  • This material can also be used to detect the production of gas (through the Durham’s tube method).

Limitations of Peptone Water

  • Due to its low food content, this is the simplest medium, but it is useless for the growth and maintenance of the fussy organism.
  • Since the pH of the Peptone Water might be influenced by the sugar solutions used, measuring the pH is required.
  • To guarantee the inoculant’s purity, subcultures on a solid media may be required. False readings are produced by growth that is polluted or otherwise mixed.
  • It’s possible that dietary differences will lead some strains to display poor growth.
  • Because of the inability to confirm the organism in this medium, further testing must be conducted on pure culture colonies using biochemical, immunological, molecular, or mass spectrometric methods.

Peptone water is a versatile medium that can be used to assess motility, antimicrobial sensitivity (when used as a diluent or suspension), indole production, the oxidation-fermentation (base) test, and as an enrichment media (pH sift) for Vibrio species. Different cultural media also rely on it as their foundation.


What is Peptone Water used for?

Peptone water is a nutrient medium that is used to support the growth of microorganisms. It is made by adding peptone, a mixture of hydrolyzed proteins, to water. Peptone water is often used in laboratory settings for the isolation and cultivation of microorganisms, as well as for the enrichment of samples for bacterial identification and testing. It can be stored at low temperatures (around 0-10°C) for a limited period of time before use.
In addition to its use in the laboratory, peptone water is also sometimes used in industrial applications, such as the production of antibiotics and other pharmaceuticals. It may also be used in quality control testing to ensure the safety and purity of products.
Peptone water can be adjusted to different pH levels, depending on the needs of the microorganisms being cultivated. For example, alkaline peptone water is used to cultivate certain types of Vibrio species, while neutral peptone water is used to cultivate a wider range of bacteria.

What is Peptone Water made of?

Peptone water is a microbiological growth medium made of sodium chloride and peptic digest of animal tissue. At 25 degrees Celsius, the medium has a pH of 7.20.2 and is rich in tryptophan. Peptone water is a nonselective broth medium that can be used as a main bacterial growth enrichment media.

What is the difference between peptone and Peptone Water?

Peptone is a type of partially digested protein that is used in the preparation of nutrient broth. It is typically derived from animal sources, such as beef or milk, and is broken down into smaller peptides and amino acids through the process of hydrolysis. Peptone is a key ingredient in the preparation of many types of media used in microbiology, including peptone water.
Peptone water is a type of nutrient broth that is made by adding peptones to water. It is a nutritious, neutral pH liquid that supports the growth of many types of microorganisms, including bacteria, fungi, and yeasts. Peptone water is commonly used as a base for preparing other types of media or as a growth medium on its own.
So, in summary, peptone is a type of protein used to prepare peptone water, which is a type of nutrient broth used to support the growth of microorganisms.

Why is Peptone Water used for dilution?

Peptone water is a solution of peptone, which is a mixture of hydrolyzed proteins, in water. It is commonly used as a diluent because it contains nutrients that can support the growth of microorganisms. Additionally, peptone water is generally a good source of water for the growth of microorganisms because it is free of contaminants and other materials that could interfere with microbial growth. In general, peptone water is used for dilution because it is a convenient and reliable source of nutrients and water for the growth of microorganisms.

What is called peptone?

Peptone is a mixture of hydrolyzed proteins that is produced by the digestion of proteins with enzymes or acid. It is commonly used as a source of nutrients for the growth of microorganisms in laboratory culture media. Peptone is typically made from animal or plant proteins, and it can be derived from a variety of sources, including milk, eggs, and plant seeds. In addition to its use in culture media, peptone is also used in the production of food products, cosmetics, and other consumer goods.

How do you increase the pH of Peptone Water?

There are several ways to increase the pH of peptone water:
1. Add a base: To increase the pH of peptone water, you can add a base such as sodium hydroxide (NaOH) or potassium hydroxide (KOH). You will need to use a pH meter or pH strips to determine the amount of base to add in order to achieve the desired pH.
2. Use a buffer: A buffer is a substance that can resist changes in pH. You can use a buffer solution to increase the pH of peptone water by adding a small amount of the buffer to the solution.
3. Use a pH adjuster: There are several commercial products available that are specifically designed to adjust the pH of solutions. These products can be added to peptone water to increase the pH.
It is important to note that the pH of peptone water can also be increased by adding other substances that are basic in nature, such as bicarbonate or carbonate ions. However, it is generally recommended to use a pH meter or pH strips to accurately measure the pH of the solution and ensure that the desired pH is achieved.

What does peptone smell like?

Appearance Tan powder. Molecular weight N/A. Odor Cooked meat.

Can bacteria grow in peptone water?

Yes, bacteria can grow in peptone water. Peptone water is a nutrient-rich medium that can support the growth of many types of bacteria. In fact, peptone water is commonly used in laboratory settings as a simple, nutritive medium for the cultivation and maintenance of bacteria. Peptone water is generally considered a good source of nutrients for the growth of microorganisms because it contains a mixture of hydrolyzed proteins, which can provide the amino acids and other nutrients that bacteria need to grow and multiply. However, it is important to note that the specific types of bacteria that can grow in peptone water will depend on a variety of factors, including the pH, temperature, and oxygen levels of the medium.

What is source of peptone?

Peptone is derived predominantly from bovine or porcine sources, including meat, internal organs, gelatin, and milk, in addition to plants and yeasts. Peptone is a partially digested protein that is produced through the enzymatic or acidic degradation of proteinaceous material.




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