Effect of oxygen delignification operating parameters on downstream enzymatic hydrolysis of softwood substrates

Enhanced oxygen delignification of softwood pulp samples (taken upstream and downstream of a commercial oxygen delignification unit) improved the initial rate of enzymatic saccharification and overall yield of monomeric sugars by 62-82% and 76-80%, respectively. Laboratory-scale experiments were used to examine the effect of a broad range of operating parameters (temperature, time, caustic concentration, and oxygen partial pressure) on the effectiveness of oxygen delignification. Using empirical models, kappa number (residual lignin content) was found to effectively predict final conversion to monomeric sugars. Application of oxygen delignification to sulfite mill knots resulted in smaller (20-25%) reduction in lignin content. However, using a combination of oxygen delignification and particle size reduction, up to 80% of the carbohydrate in the reject knots could be converted to fermentable sugars.