Optimization of microwave-assisted calcium chloride pretreatment of corn stover

A 62.5% (w/w) CaCl2 solution was used in the microwave pretreatment of corn stover. The central composite design (CCD) of response surface methodology (RSM) was employed to design and optimize the CaCl2-assisted microwave pretreatment (CaCl2-pretreatment). Temperature and time were the main factors affecting the enzymatic digestibility of corn stover. After CaCl2-pretreatment, hemicellulose degradation reached 85.90%, the specific surface area (SSA) increased by 168.93%, cellulose crystallinity index (CrI) decreased by 13.91% compared to untreated corn stover. The optimal conditions for glucose production with the CaCl2-pretreatment obtained by CCD were, 162.1 °C, 12 min and solid-to-liquid ratio 10% (w/v). Under these conditions, the enzymatic hydrolysis ratio of cellulose was 90.66% and glucose recovery was 65.47%. This novel process achieved the temperature of about 160 °C necessary for lignocellulose pretreatment under atmospheric pressure using the cheap calcium chloride as the heating medium.

► CaCl2 was used as a microwave medium for corn stover pretreatment.
► Central composite design was employed to optimize the CaCl2-pretreatment.
► The optimal conditions for corn stover glucose recovery were: 162.1 °C, 12 min.
► CaCl2-pretreatment degraded up to 85.90% of the hemicellulose in corn stover.