Ozonolytic Delignification of Wheat Straw

The dynamics of wheat straw delignification with ozone treatment is studied. The dependence of the residual lignin content on the specific absorption of ozone is determined. It is found that in a prolonged stage of ozonation, ozone is consumed mostly for the reaction with lignin. HPLC is used to record kinetic profiles of water-soluble products of ozonation. The IR spectra of straw samples with various degrees of delignification are analyzed. The results confirm the ozonolytic degradation of lignin and suggest that polysaccharides undergo partial oxidation during prolonged ozonation. A relationship is found between the lignin content and the reactivity of ozone-pretreated straw in enzymatic hydrolysis to sugars. The optimum consumption of ozone is 2 mol-equiv O-3 per phenylpropane structural unit (PPU) of the lignin contained in the straw, which corresponds to a residual lignin content of similar to 10%.