Systems and methods for improving ethanol yield are provided. A feedstock is ground suitably fine for use in fermentation. The feedstock may include corn or any other suitable material. In some cases, the feedstock undergoes a fractionation prior to grinding. The ground feedstock may be slurried with water and enzymes to facilitate conversion of the starch in the feedstock to sugars. The slurry may be about 35% solids. After being slurried, an ethanologen may be added. Additionally, the pH of the slurry may be adjusted to between 4.2 and 5.2 to facilitate the priming A primer is added to the slurry. The primer may include any weak acid, and in some embodiments includes acetic acid. Acetic acid, when used as a primer, may be added at a concentration of between 1200 and 3600 parts per million. The slurry is fermented to produce improved yields of ethanol.