In 1883 Emil announced his system of pure yeast cultures. He revealed that ‘bad beer’ was not only a result of bacterial infection, as French biologist, Louis Pasteur had assumed, but contamination by wild yeast. Until then brewers re-used beer from previous fermentations. Isolating yeast meant they could use “fresh” clean yeast every time, significantly improving the brewing process and taste consistency. He then worked to isolate a single cell of good yeast and propagated it into a pure culture. The new “Carlsberg bottom yeast n.1” was used for the first time, and with great success, on a production scale in November 1883.