Pilot-scale submersed cultivation of R. microsporus var. oligosporus in thin stillage, a dry-grind corn-to-ethanol co-product

An innovative process to add value to a corn-to-ethanol co-product, Thin stillage, was studied for pilot-scale viability. A 1500L bioreactor was designed, operated, and optimized to cultivate Rhizopus microsporus var. oligosporus via submersed fermentation in Thin Stillage. The biomass was harvested and processed into a feed suitable for storage and ultimately for animal feeding trials. Characterization of the biomass and feed trials revealed that there is substantial potential as a nutrient dense feed supplement with 41.1% protein, 26.3% fat, and metabolizable energy on s dried basis. The amino acid profile is superior to that of DDGS, with most notably 1.7% Lys on dried basis. This process produces a significantly more nutrient dense product than DDGS, and could increase water-reclaimation in a dry-grind corn to ethanol plant. Industrially it would replace the energy intensive process of converting thin stillage into syrup that adds only $10-25/ton to DDG, while maintaining production of DDG. Using thin stillage as used a growth media for R. microsporus var. oligosporus, should not only lead to saving in energy costs, but also generate a high-value co-product which could lead to economic gains. Also there is still unexplored potential of enzymes, chitin, and co-culturing to further add value