Alkaline Hydrogen Peroxide (AHP) Pretreatment of Corn Stover

Researchers from the University of Michigan (United States) report the use of alkaline hydrogen peroxide (AHP) for the pretreatment of corn stover (leaf- and stalk- residues of the corn plant after harvest). Pretreatment is usually the first step in the processing of lignocellulosic biomass (such as corn stover) into biofuel ethanol. Its objective is to remove the tight lignin wrapping around the biomass, and to expose/transform the carbohydrate fractions (cellulose/hemicellulose) so that these are easier to process into ethanol-fermentable sugars.

Hydrogen peroxide (H₂O₂) is an oxidizing chemical which is commonly used as a disinfectant. It's oxidizing ability is considered sufficient for lignin removal in oxidative pretreatment processes. A mixture of hydrogen peroxide and sodium hydroxide constitutes AHP. The use of AHP is considered to have the following advantages:
(1) the chemicals (hydrogen peroxide and sodium hydrogen peroxide) are considered "environmentally benign",
(2) operating temperatures are milder (21 ^oC to 50 ^oC, in contrast to other treatments with operating temperatures higher than 100 ^oC),
(3) the chemical cost compared to the use of other effective pretreatment chemicals (such asa ionic liquids and phosphoric acid/ethanol) are lower.

The researchers studied the effects of biomass loading, hydrogen peroxide loading, residence time, and pH control, in combination with subsequent enzymatic digestion (using a commercial enzyme preparation, optimized mixtures of four commercial enzymes, or optimized synthetic mixtures of pure enzymes). They found that a combination of a biomass loading of 10%, a hydrogen peroxide loading of 0.5 g/g biomass, and the use of a commercial enzyme mixture at a protein loading of 15 mg/g glucan gave a monomeric glucose yield of 95%.

They concluded that AHP can be a good pretreatment method for corn stover, but additional improvements in the AHP process, such as peroxide stabilization, peroxide recycling, and improved pH control, could be helpful. The full results of the study is published in the open access journal, Biotechnology for Biofuels (URL above).