Viability Assays - Erythrosin B vs. Methylene Blue

Erythrosin B 

Erythrosin B is our preferred yeast cell viability stain because it produces clear, easy-to-interpret results, it is non-toxic, and it is shelf stable. Also it dyes dead yeast cells a fun vibrant pink colour.

How does it work? Erythrosin B works by entering into non-viable cells where it concentrates and is visible as a pink dye. In living cells, the cell membrane is intact which keeps Erythrosin B from entering. This is how most other cell stains such as Trypan Blue work. 

Curious to learn more? Check out our blog post on cell staining with Erythrosin B.

Methylene Blue - how does it work and what are its limitations? 

Methylene blue staining works differently from Erythrosin B and Trypan Blue. With methylene blue, the stain enters all cells. Cells with active enzymes are able to break down the stain, while dead cells lacking active enzymes are not, and stain a dark blue. A known limitation of methylene blue is that recently dead cells tend to stain a "medium blue" because they may still have partially intact enzyme function. This makes accurate quantification of yeast slurry viability difficult when viability drops below about 80% or so. For this reason, we recommend Erythrosin B (or Trypan Blue) for beer yeast viability stains. 

A yeast sample stained with methylene blue, showing varying shades of blue staining.
Example of the same culture stained with Erythrosin B (clearer results). 

Photo Credit: Emilia Fytikas

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