Description
Yeast extract agar is a non-selective, nutrient-rich biological media used for the cultivation and enumeration of a wide spectrum of bacteria, yeasts, and molds. It is particularly known for its use in water quality testing to count viable microorganisms.
Key ingredients and their function
The exact formula can vary between manufacturers, but the core components and their functions remain consistent:
- Yeast Extract: This is a key nutrient source, providing a rich blend of B-complex vitamins, amino acids, peptides, and other essential growth factors that support robust microbial growth.
- Peptone or Casein Enzymic Hydrolysate: A source of nitrogenous compounds, amino acids, and minerals. Some formulations, like Tryptone Yeast Extract Agar, use casein enzymic hydrolysate, also known as tryptone.
- Agar: This is a solidifying agent that gives the medium its gel-like consistency, allowing microorganisms to grow in isolated colonies.
- Dextrose (Glucose): In some variations, like Yeast Extract Peptone Dextrose (YPD) agar, dextrose is added as a fermentable carbon source to promote more vigorous growth, especially for Saccharomyces cerevisiae
