Two-stage processing of Miscanthus giganteus using anhydrous ammonia and hot water for effective xylan recovery and improved enzymatic saccharification

A two-stage method using gaseous ammonia and hot water was proposed to recover xylan and lignin from Miscanthus. In this method, Miscanthus was treated with gaseous ammonia at elevated temperatures (60-150 °C) for various reaction times (1-48 h) in the first stage, termed as LMAA (low-moisture anhydrous ammonia) treatment. In the following stage, the LMAA-treated solid was subjected to hot-water treatment in a flow-through column reactor under various reaction conditions (170-220 °C, 30-90 min). After two-stage processing, the remaining solid contained mostly glucan (∼80% cellulose), which became highly digestible by enzymes. The optimal treatment conditions for sugar recovery using two-stage process were 120 °C and 12 h for the 1st stage and 190 °C, 90 min, and 5 mL/min for the 2nd stage, which resulted in 84.2% xylan recovery in liquid phase and 95.3% glucan digestibility of the treated solid, using 15 FPU/g-glucan enzyme loading after the two-stage treatment.