Yeast Extract Agar
Also known as：YEA · Tryptone Yeast Extract Agar · Water Plate Count Agar
Yeast Extract Agar is a nutrient agar recommended for plate count of microorganisms in water.
- Category
- Dehydrated Culture Media
- Dissolve per litre
- 24 g
- Pack sizes
- 500 g · 5 kg · 25 kg
- Certifications
- Halal
- Standard methods
- ISO 6222
Data updated：2026-11-06
Brand cross-reference：Oxoid Yeast Extract Agar · Merck Yeast Extract Agar（ISO 6222） Brand cross-reference
- Allergens
- Milk
Overview
Yeast Extract Agar is an agar (solid) medium. Yeast-extract based, used for heterotrophic plate counts of drinking water and general bacterial culture. STBIO manufactures it from food-grade raw materials in an ISO 22000 certified facility, with a COA for every batch. This is the Halal-certified version.
Principle
Yeast Extract Agar is a low-nutrient, non-selective medium specified for the enumeration of culturable microorganisms in water.¹ Enzymatic digest of casein supplies nitrogen, amino acids, and peptides, and yeast extract provides B-group vitamins and other growth factors. The modest nutrient content favours the recovery of the naturally occurring bacteria of water, which may be inhibited by richer media. Plates are prepared by the pour-plate technique and incubated at two temperatures: incubation at 22°C enumerates the general water flora, while incubation at 36°C indicates organisms more likely to be of human or animal origin. Changes in either count are used to assess the quality and consistency of water supplies and treatment.²
Directions
Suspend 24 g of powder in 1 L of purified water. Heat with continuous stirring and bring to the boil for 1 minute. Sterilize by autoclaving at 121°C for 15 minutes. Cool to 45-50°C and use for the pour-plate technique. Test the finished medium for performance using stable, standard control cultures.
Cultural response
| Test organism | ATCC | Growth |
|---|---|---|
| Escherichia coli | 25922 | good-luxuriant |
| Bacillus subtilis | 6633 | good-luxuriant |
| Pseudomonas aeruginosa | 27853 | good-luxuriant |
Product highlights
- Halal certified, suitable for the Malaysian, Indonesian, and Middle Eastern markets
- Manufactured to the standard formulation, 24 g per litre
- Performance verified against standard control strains before release (Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa)
- Available in 500 g / 5 kg / 25 kg, from laboratory to industrial scale
- COA, specification sheet, and technical data sheet available; samples on request
- Manufactured in Taiwan with reliable supply
Frequently asked questions
01How much powder per litre?
Use 24 g per litre of deionised water; preparation and sterilisation conditions are given on the specification sheet.
02Which organisms is it suitable for?
Total Plate Count, Aerobes, Environmental monitoring, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa. See the cultural response table and the specification sheet.
03What are the equivalent brand products and standard methods?
Cross-reference: Oxoid Yeast Extract Agar, Merck Yeast Extract Agar. Standard methods: ISO 6222. Formulations may differ slightly between makers; refer to the specification sheet.
04How is this product prepared?
Suspend 24 g of powder in 1 L of purified water. Heat with continuous stirring and bring to the boil for 1 minute. Sterilize by autoclaving at 121°C for 15 minutes. Cool to 45-50°C and use for the pour-plate technique. Test the finished medium for performance using stable, standard control cultures.
05How do I request a bulk quotation, and can you provide a COA?
Yes. This product is available in 500 g, 5 kg, 25 kg. Tell us your application and volume when requesting a quotation; we reply within one working day and can supply the COA, specification sheet, and technical data sheet.
Academic citation
Products from this range have been cited as the culture media source in a peer-reviewed study by a National Taiwan University research team:
Chan et al. (2024). Single-strain probiotics enhance growth, anti-pathogen immunity, and resistance to Nocardia seriolae in grey mullet (Mugil cephalus) via gut microbiota modulation. Animal Microbiome, 6, 67. Springer Nature.
Media attribution: Tryptone Soy Broth, MRS medium, LB broth, beef extract, peptone, yeast extract, agar (STBIO, New Taipei, Taiwan)
Read the full paperUsed in these applications
Further reading
References
- 1. ISO 6222, Water quality — Enumeration of culturable micro-organisms — Colony count by inoculation in a nutrient agar culture medium, International Organization for Standardization, Geneva.
- 2. Atlas R. M., 2010. Handbook of Microbiological Media, 4th Ed., CRC Press, Boca Raton.