Ethanol from wheat straw cellulose by wet oxidation pretreatment and simultaneous saccharification and fermentation

Alkaline wet oxidation (WO) was used as a pretreatment method for fractionation wheat straw to a solubilised hemicellulose and a solid cellulose fraction. The WO was performed at initially 6% dry (solid) matter content. In the process the hemicellulose was solubilised and some of the lignin and pectin substances oxidized, resulting in a final solid matter content of 3% in the hydrolysate. By filtration, the solid cellulose product was increased to 10% dry matter that was effectively hydrolyzed and fermented to ethanol by simultaneous saccharification and fermentation (SSF) process using the filtrate as process water. The compact fermentation bulk was liquefied by enzyme treatment prior to the SSF in order to decrease the viscosity and facilitate good mixing conditions during the fermentation. The lipophilic compounds associated to the surface of wheat straw remained in a more concentrated form in the solid fractions after WO and SSF.