Intensification of sodium hydroxide pretreatment of corn stalk using magnetic field in a fluidic system

• This method shortened CS NaOH pretreatment time by 33.3%.
• Sugar release rose by 23 mg in 2–6 Hz and fell by 18 mg from 1 g dry CS in 6–10 Hz.
• High flow rate is conducive to the increase of sugar yield.
• RSM was used to optimize key processing parameters for maximal sugar yield.
• Optimal conditions were 6.71 Hz, 0.50 L/min and 1.02% NaOH for CS pretreatment.

To promote NaOH pretreatment of corn stalk (CS), a continuous processing system uniting magnetic field and millimeter-scaled channel flow was established. First, four comparative pretreatments were conducted: (I) CS was pretreated with NaOH under traditional agitation; (II) CS was pretreated with NaOH in a flowing state inside the millimeter-scaled channel; (III) CS was pretreated with NaOH in a flowing state and under a static magnetic field; or (IV) CS was pretreated with NaOH in a flowing state and under a rotating magnetic field. By comparison, the highest pentose (121.22 mg/g dry CS) and hexose (287.04 mg/g dry CS) yields were obtained in the shortest pretreatment time with Pretreatment IV (8 h). Accordingly, the key parameters of Pretreatment IV were optimized as 6.71 Hz frequency, 0.50 L/min flow rate, and 1.02% NaOH concentration. Under these conditions, 439.24 mg sugars were released by 1 g dry CS during pretreatment and enzymatic hydrolysis.