Starch casein agar (SCA)
- Starch casein agar can be described as an nutrient-rich medium that is used for the cultivation and growth of the saccharolytic marine bacteria.
- As the name implies, contains starch as the primary carbohydrate source.
- This medium is used primarily to cultivate and isolate the presence of actinomycetes in different sources, including marine sediments and soil.
- Starch Casein agar is composed of seawater, which is a rich source of nutrients, vitamins, as well as sea salts that aid in the growth of marine residents and actinomycetes comprise an important portion of the soil lakes, rivers, and muds.
- The starch contained in the agar provides the saccharolytic organism to have enough nutrients to make their carbohydrate and protein.
- Actinomycetes are fungi-like species which have recently attracted greater interest because of their role not just in the field of therapeutics, but as well in the recycling of organic matter.
- Historically, actinomycetes were separated from terrestrial sources, but in recent years, the existence for actinomycetes within marine sediments has been found.
- Marine sediments are recognized as potential sources of isolation of novel Actinomycetes that produce new products. They are acknowledged as a source for innovative antibiotics and anticancer drugs.
Composition of Starch casein agar (SCA)
Starch casein agar comprises starch, which is the principal carbon source, as well as casein, which is a major source of proteins and seawater. The precise nature of Starch Casein Agar is described below:
| Ingredients | Gram/liter |
| Soluble starch | 10.0 |
| Casein (Vitamin free) | 0.30 |
| KNO3 | 2.0 |
| MgSO4.7H2O | 0.05 |
| K2HPO4 | 2.0 |
| NaCl | 2.00 |
| CaCO3 | 0.02 |
| FeSO4.7H2O | 0.01 |
| Agar | 18.0 |
Final pH at 25°C: 7.3 ±0.2
The composition of the HiMedia Starch Casein Agar is given below:
| Ingredients | Gram/liter |
| Starch | 10.0 |
| Casein | 1.0 |
| Seawater | 37.0 |
| Agar | 15.0 |
Final pH at 25°C: 7.2 ±0.2
Principle of Starch casein agar (SCA)
The agar Starch Casein is made by combining various nutrients that allow for the development of a wide variety of microorganisms that typically don’t develop in a standard medium such as Nutrient agar since they require particular nutrients or other supplements. The main components that make up the media include starch, casein, and seawater.
Alongside these, other minerals and trace ingredients that are essential to the development of bacteria are included. Starch is the primary source of carbon that is essential for saccharolytic organisms such as Actinomycetes and different marine bacteria. The casein is the principal protein source that is vital for the creation of amino acids in bacteria.
It also has other components such as vitamins, various organic compounds, trace minerals as well as salts that can further boost the growth of various organisms. Additionally, seawater has sea salts that provide complex ionic sources, which ensure that the medium is appropriate for the marine microbial life and protects it from the elements. It also helps prevent the changes in the pH of the medium in the course of growth.
The distillation process provides an environment to dissolve nutrients, making it simpler for bacteria to take them in. Agar is a solidifying agent that creates a firm surface for the organisms to develop on. This allows the examination of the morphology of colonies and the enumeration that the living thing. The medium is comprised of these nutrients , which are vital to a range of species, making it a universal medium that is suitable to serve a variety of purposes.
Intended Use
Starch Casein Agar is recommended for the detection of marine saccharolytic bacteria.
Type of Specimen: Marine isolates.
Preparation of Starch casein agar (SCA)
- In a beaker, 63 grams of lab-prepared or dehydrated powder is mixed with 1000 milliliters of deionized or distilled water.
- This suspension then gets heated until boiling, allowing the medium to dissolve completely.
- The medium that has been dissolved is autoclaved at a pressure of 15 pounds (121degC) for 15 minutes.
- When the autoclaving process has been completed, the beaker will be removed and chilled to temperatures of around 40-45 degC.
- It is then put onto sterilized Petri plates in sterilized conditions.
- When the media is becoming solid, the plates are ready to be placed in the hot oven on a lower setting for a couple of minutes to dry out any moisture on the plates prior to use.
Storage of Starch casein agar (SCA)
- The powdered media in its form should be kept between 10 and 30 degC in a tightly sealed container. The ready-to-use medium should be kept between 20 and 30 degrees Celsius.
- Once the bottle has been opened, bottle should be stored in a dry state and sealed tightly around the bottle to avoid lump formation since the product is hygroscopic by the nature, which means it retains moisture very quickly.
- The container must be kept in a dry and ventilated space shielded from extreme temperatures and ignition sources.
- The product must be used up before the expiry date listed on the label.
Result Interpretation on Starch casein agar (SCA)
The media form a yellow-colored transparent to slightly opalescent liquid in Petri plates. The table below illustrates the expansion of medically important bacteria as well as Actinomycetes and their colony morphologies Starch Casein Agar:
| Organism | Growth | Colony Morphology |
| Actinomycetes | Luxuriant | White to light yellow colored colonies with powdery colonies. Some colonies might be circular to pinpoint colonies that are powdery on the top surface and mucoid at the bottom within 1-3 days of incubation. Complete powdery colonies form after 7 days of incubation. |
| Streptococcus limosus | Good-luxuriant | Smooth colorless colonies with a diameter range of 2-4 mm. The coloration of the colonies might differ. |
| Streptomyces praecox | Good-luxuriant | Golden yellow colored circular, convex and smooth colonies of the diameter range of 2-4 mm; opaque colonies. |
| Vibrio cholerae | Good-luxuriant | Circular, colorless to yellow colored colonies of the size 0-5 to 1 mm in diameter. Light yellow colored with low convex elevation; mucoid colonies. |
Quality Control
- Dehydrated Appearance: Off white to yellow coloured, homogenous, free flowing powder.
- Prepared Appearance: Off white to yellow coloured, clear to slightly opalescent gel forms in petriplates.
- Cultural Response: Characteristics of culture that are observed following an incubation period of 18-48 hours in a temperature range between 35degC and 37deg.
| Organism (ATCC) | Growth |
| Streptococcus limosus (19778) | Good |
| Streptomyces praecox (3374) | Good |
| Vibrio cholerae (15748) | Good |
Application of Starch casein agar (SCA)
- Starch Casein Agar is utilized for the separation of saccharolytic bacterial species, mostly from marine origins.
- It is the most common way to isolate as well as cultivation of actinomycetes derived from various marine and terrestrial habitats.
- It can also be utilized for studies that study the microbial ecosystems of the environment because it aids in the growth of fungi, bacteria and actinomycetes.
- Starch Casein Agar is suggested by the standard methods of preservation and isolation of cultures of actinomycetes for a longer time.
Limitations of Starch casein agar (SCA)
- The nutritional variations that appear in the media could cause a slow growth rate in these media.
- In order to confirm the organism’s health, a variety of biochemical tests must be conducted.
References
- https://microbiologyinfo.com/starch-casein-agar-sca-composition-principle-uses-preparation-and-result-interpretation/
- https://www.microxpress.in/uploads/product/starch-casein-agar_technicaldetails_57920200808.131624.pdf
- https://www.researchgate.net/figure/Composition-of-Starch-Casein-Agar-SCA-g-l_tbl1_313725757
