Methods and systems for propagation of a microorganism using a pulp mill and/or a paper mill waste by-product, and related methods and systems

A method of propagating a microorganism, the method comprising:

• a) combining at least one pulp or paper mill waste by-product and an ionic stabilizing component, wherein the at least one pulp or paper mill waste by-product is chosen from a pulp sludge, a paper sludge, and combinations thereof, wherein the ionic stabilizing component is chosen from one or more salts, at least one stillage composition, corn steep liquor, at least one pulp or paper mill waste by-product liquor, and combinations thereof, and wherein the at least one stillage composition is derived from a grain starch ethanol process,
• b) enzymatically hydrolyzing one or more polysaccharides and/or one or more oligosaccharides present in at least one pulp or paper mill waste by-product in the presence of one or more enzymes and into one or more monosaccharides, wherein the one or more enzymes are chosen from one or more cellulase enzymes, one or more hemicellulose enzymes, and combinations thereof;
• c) providing a first cell mass of a microorganism that can convert one or more monosaccharides into a biochemical via fermentation;
• and
• d) propagating the first cell mass of the microorganism in a propagation composition that comprises one or more monosaccharides from the enzymatic hydrolysis as a carbon source to propagate the first cell mass of the microorganism into a second cell mass of the microorganism.