Water solubilization of DDGS via derivatization with phosphite esters

Ethanol production from corn starch in the corn dry milling process leaves Distillers’ Dry Grains and Solubles (DDGS) as a major by-product from which additional ethanol may be economically obtained from its glucan content. A challenge in processing the cellulose content of this material lies in its extensive inter-cellulose chain hydrogen bonding, which inhibits access of enzymes capable of cleaving glycosidic bonds, a transformation required for providing fermentable sugars. The phosphitylation of cellulosic OH groups using a reactive bicyclic phosphite ester is utilized to disrupt cellulosic hydrogen bonds, thus providing access to cellulose chains for further processing. We describe a method of pretreating DDGS with commercially available trimethylolpropane phosphite [P(OCH2)3CEt] in the presence of a slight molar excess of water to afford greater than 90% DDGS solubility in the reaction mixture in methanol and in water. Preliminary results using a model compound [d-(+)-permethylated cellobiose] indicate that glycosidic bonds are cleaved as a consequence of this pretreatment.