Yeasts, unicellular eukaryotes, are a well-studied model organism in molecular genomics. They are chemoorganotrophs because they use organic compounds for energy. Yeast extract peptone, or YEPD), Growth Agar is used to maintain and propagate yeasts. YPD is a complete medium that allows for yeast growth.
Composition of YEPD Agar
| Ingredients | Gms/liter |
| Peptone | 20.000 |
| Yeast extract | 10.000 |
| Dextrose | 20.000 |
| Agar | 15.000 |
Final pH (at 25°C): 6.5±0.2
Principle of YEPD Agar
YEPD is made up of yeast extract, peptone and glucose or dextrose. A minimal medium that contains only salts and dextrose is ideal for yeast growth. Adding yeast cell extract hydrolysates and protein to the medium allows for faster growth, whether you are in log-phase or exponential growth. Yeast extract is a source of B-complex vitamins, and contains all the necessary amino acids for growth. Peptone is the main source of nutrients, vitamins, and minerals. Dextrose is the carbon source. This medium supports vigorous growth of both wild and mutant types of budding yeast.
Preparation of YEPD Agar
- In 1 liter of purified tap water, you can suspend 65 grams of the powder.
- Mix well.
- To dissolve the powder, heat the agar medium over high heat.
- For 15 minutes, autoclave the broth media and agar at 121°C.
- Keep it at 45-50oC
- You can also put the same amount of food into Petri dishes.
Result Interpretation on YEPD Agar
| Organisms | Growth |
| Kluyveromyces lactis | Luxuriant growth |
| Saccharomyces cerevisiae | Luxuriant growth; smooth, moist, glistening colonies |
| Candida albicans | Luxuriant growth |
Uses of YEPD Agar
- YEPD can be used to grow yeast cultures.
- It is used to grow Saccharomyces cerevisiae.
- This medium is suitable for most heterotrophic microorganisms. However, because of their simplicity they are used as the base media for routine yeast cultivation.
- It is used to prepare culture media for molecular microbiology processes.
Limitations of YEPD Agar
- It is non-selective.
- YEPD is a complete medium and cannot be used to test for auxotrophs.
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