Suppose I wanted to make some ethanol fuel. Normally, I would get yeast, mix with water, add sugar and wait. However, there is an enzyme (zymase) in yeast that does this. Looking at the Wikipedia article for zymase, someone managed to extract it using only quartz and diatomaceous earth.
The advantages of this is that it could potentially produce large amounts of concentrated ethanol, whereas yeast could only produce less than 20% due to it dying. So, do people use such a method, and if not, why not?