Kirsten Sterrett, a University of Colorado graduate student, first became interested in if and how beer could be brewed in space while working at the Coors Brewing Company. Having studied aerospace engineering as an undergraduate, she began to wonder: How would yeasts that perform fermentation under the tug of Earth's gravity fare in orbital free fall?
The behaviour of the yeast was somewhat puzzling, though. The total cell count in space-borne samples was lower that of "control" samples brewed on the ground, and the percentage of live cells was also lower. One of the yeast's proteins also existed in greater amounts in the space-brew.
Sterrett's experiment couldn't suggest reasons for these changes, but the overly abundant protein bears some resemblance to a general stress protein.
The low cell count was particularly surprising, says Sterrett. In space, yeast cells remain evenly dispersed within the "wort" - a brewers' term for the pre-fermentation mixture of water, barley, hops, and yeast. Ideally, this would give the yeast cells better access to nutrients in the wort compared to similar mixtures on Earth, where the weight of the cells causes them to pile at the bottom one on top of the other.