High yield of fermentable sugar from paper mulberry woods using phosphoric acid plus hydrogen peroxide pretreatment: Multifactorial investigation and optimization

Abstract

Paper mulberry wood contains a high cellulose content of 59%, making it a potentially excellent feedstock for recovery of fermentable sugar used in bioethanol production. This potential was usefully exploited by establishing the optimal phosphoric acid plus hydrogen peroxide pretreatment of its woods using the response surface methodology. Pretreatment temperature, H3PO4 proportion in pretreatment mixture, and time significantly corelated with the removal of non-cellulosic polymers, cellulose recovery, enzymatic hydrolysis of the recovered cellulose, and glucose yield. At the optimized conditions of 34.7 ⁰C, 71.3% w/w H3PO4 proportion (the corresponding H2O2 proportion of 4.84% w/w), and 3.3 h, there were 97% biomass delignification, 100% hemicellulose removal, and high recovery of a cellulose-rich substrate characterized by decreased crystallinity, enhanced porosity, and complete glucose digestibility. The obtained high glucose yield of 493 mg/g raw wood was comparable to the best-reported yields from short-rotation woody energy crops.