Methods of and device for separating germs from grains used for alcohol production are provided. The principle of density difference is able to be used to separate germs from a slurry. By adjusting the density and/or viscosity of the slurry, higher germ recovering rate is attended. The method of adjusting the density and/or viscosity includes recycling a cook-water to reduce the viscosity of the slurry before fermentation and pre-concentrating a whole stillage at an evaporator and adding a syrup to the whole stillage after fermentation. An air flotation unit is able to be used to increase oil and germ recovery rate.
