Emil Christian Hansen Isolates A Single Yeast Cell

In 1883, Emil Christian Hansen of the Carlsberg Laboratory in Copenhagen developed a method for obtaining a pure yeast culture from a single cell. By repeatedly diluting brewery yeast and propagating selected cells in sterile wort, Hansen could separate individual yeast types that had previously remained mixed together in normal brewery cultures. His experiments distinguished a suitable bottom-fermenting strain, initially called Unterhefe No. 1, from contaminating yeasts capable of causing beer spoilage. Hansen’s single-cell method gave brewers a systematic way to identify, preserve, and reproduce a selected yeast strain instead of relying on mixed yeast collected from an earlier fermentation. It established the scientific basis of pure-culture brewing and made yeast management more controllable. The successful production-scale introduction of Hansen’s culture at Carlsberg in November 1883 forms a separate milestone in the timeline.