Fractionation of Wheat Middlings into Starch, Proteins, and Lignocellulosic Residues

Wheat middlings are a heterogeneous byproduct from wheat milling, representing 30.0 wt % of the wheat kernel. It can contain 20.0 wt % starch and 13.7 wt % crude protein (dry basis), along with cellulose, hemicellulose, lignin, and inorganics. In this work, we present washing processes designed to maximize the removal of starch and crude protein from wheat middlings. A combined design of experiments (DOE) and Bayesian optimization (BO) approach was implemented to identify the optimal operating conditions for removal in water. Inorganics can be removed using a water-washing step, and proteins are minimally removed during the water washing process. Subsequently, protease enzymes were used to further remove proteins from wheat middlings. Using this strategy, up to 95% of starch and 84% of crude protein were removed from wheat middlings. The resulting residue, characterized by reduced starch and protein content, provides biorefineries with a cleaner biomass feedstock for fuels and chemicals production.