DKO stands for Diacetyl Knock Out, and it is a series of familiar yeast strains engineered to knock out the formation of diacetyl before it starts. Each strain expresses the ALDC enzyme, allowing you to streamline efficiency and quality without the diacetyl hang-up.

Omega Yeast Diacetyl Knock Out (DKO) artwork

What’s ALDC?

ALDC (alpha-acetolactate decarboxylase) is an enzyme that breaks down alpha-acetolactate, the precursor for diacetyl, within the yeast cell. ALDC converts the precursor into a flavorless compound called acetoin. Many brewers use ALDC at the start of fermentation to help avoid the formation of diacetyl, which saves on tank time. However, ALDC is pH-sensitive and can be less effective as the pH level drops during fermentation (typically below 5), meaning that it might not be super helpful in the case of hop creep. ALDC is a proactive, rather than reactive, solution; it won’t help you clean up diacetyl once it’s already in the beer.


ALDC in cell converts a‑acetolactate directly to acetoin; without ALDC a‑acetolactate is excreted and becomes diacetyl OR with exogenous ALDC, it becomes acetoin in the beer.

Why use DKO strains as opposed to adding the enzyme?

When ALDC is expressed in the cell it converts alpha-acetolactate to acetoin directly within the cell, therefore preventing alpha-acetolactate from building up and being excreted into the beer where it will turn into diacetyl. Another bonus to ALDC activity within the cell is that it will continue working even during later stages of fermentation, which can help prevent the diacetyl that forms during hop creep.

We see the DKO series as an added layer of quality assurance with the bonus of time and cost savings. Even with great yeast management, having ALDC expressed in the cell increases efficiency in the brewery by reducing tank time. Without the need for a lengthy diacetyl rest, your beer can be turned around faster with more confidence that diacetyl won’t be delaying your production schedule. Plus, breweries can save additional costs by not buying exogenous ALDC.

Will every strain be added to the DKO series?

In short, no. Some strains are more prone to accumulating diacetyl at the end of fermentation — especially with heavily hopped beers — and are ideal candidates for this modification. While diacetyl can be avoided and kept to a bare minimum with healthy yeast and properly managed fermentation, using DKO series strains can give brewers more predictable outcomes and save time on troubleshooting and problem-solving.

Extra Special Diacetyl Graph v 4

Which strains are in the DKO series?
View DKO strains

  1. Bayern Lager DKO (OYL-433)
  2. British V DKO (OYL-431)
  3. DIPA DKO (OYL-436)
  4. Extra Special DKO (OYL-432) Formerly British Ale VIII
  5. German Lager I DKO (OYL-437)
  6. Kolsch II DKO (OYL-435)
  7. Point Loma DKO (OYL-434) Formerly West Coast Ale III
  8. West Coast I DKO (OYL-430)

How do I order?

Available now in the US for Probrew orders.

Learn more about diacetyl on our educational website.