Best Practices - Diastaticus

About Diastaticus 

Saccharomyces cerevisiae var. diastaticus is beer yeast that can break down longer-chained carbohydrates (dextrins and starches) that regular yeast can’t. This is due to the presence of a gene called STA1. The yeast doesn’t actually consume them directly, but it secretes an enzyme (glucoamylase) that breaks down dextrins outside the cell into smaller sugars that the yeast can then metabolize. Diastatic yeast is often problematic for brewers, causing unintended hyperattenuation and secondary fermentation post-packaging, which can lead to over-carbonated product and the dreaded exploding cans.

Diastatic yeast isn’t always a contaminant. Many commonly used yeast strains are diastatic. For example, most Saison yeasts contain the glucoamylase gene, which helps these strains produce a dry beer. Diastatic yeasts are killed by the same cleaning regimens which eliminate other contaminants in the brewery. However, a brewery using both diastatic and non-diastatic yeast in the same facility and with the same packaging equipment must exercise caution. Separate tanks, gaskets and hoses are recommended, as is a thorough CIP of packaging equipment after a beer produced with a diastatic yeast has been packaged.  

Because this is such an important issue, a lot of research has gone into detection testing for diastaticus. There are several ways to do this, and we’ve been looking into the most accurate and dependable ways to get results.  Here at Escarpment Labs, we use 2 methods: PCR and agar plating. The PCR method tests directly for STA1, a gene that encodes a secreted glucoamylase enzyme. Plating either screens for traits correlated to diastatic yeasts (like copper resistance on LCSM) or directly for starch consumption. 

Summary of EYL strains that grow on LCSM agar:

Additional resources

Demystifying Diastaticus part 1
PCR update (STA1 upstream sequence)
Diastaticus 101 on YouTube