Methods and systems for propagating microorganisms on stillage compositions

A method of propagating microorganisms to increase the quantity of the microorganisms in a composition for subsequent use, the method comprising:

• adding an enzyme component to a stillage-containing composition comprising stillage, wherein the enzyme component is added in an amount to convert starch into one or more monosaccharides to grow a first cell mass of the microorganism to form a second cell mass of the microorganism, wherein the enzyme component comprises alpha-amylase, gluco-amylase, or combinations thereof, wherein the stillage is obtained from a starch-based fermentation process and the stillage comprises polysaccharides, wherein the polysaccharides comprise the starch, wherein a majority of the polysaccharides in the stillage-containing composition are from the stillage;
• and
• growing the first cell mass of the microorganism in a propagation medium comprising the one or more monosaccharides from the stillage-containing composition while aerating the propagation medium to promote aerobic respiration instead of anaerobic fermentation and production of ethanol by the microorganisms to form the second cell mass of the microorganism, wherein growing is performed for a period of time in the range of 8 to 80 hours, wherein the second cell mass of the microorganism is greater than the first cell mass of the microorganism, wherein the quantity of microorganisms is increased in the second cell mass from the first cell mass, and wherein the second cell mass is at least 10 times the first cell mass,
• wherein the growing is performed entirely simultaneously while the enzyme component converts the starch into the one or more monosaccharides in the propagation medium, and wherein the starch is converted into one or more monosaccharides using the alpha-amylase, gluco-amylase, or combinations thereof to grow the first cell mass for the period of time in the range of 8 to 80 hours to form the second cell mass.