Fractionation of corn stover by two-step pretreatment for production of ethanol, furfural, and lignin

Abstract

The comprehensive utilization of lignocellulose is great importance for improving the economic feasibility of biomass refining industry. Here, we established a two-step pretreatment process for fractionation and production of multiple products (furfural, ethanol, and lignin) from corn stover (CS). In the first step, H2SO4 pretreatment was used to remove hemicellulose and the effect of solid/liquid ratio (SLR) was investigated. The hemicellulose containing washing liquor was treated for furfural production without any additional catalyst and the maximum furfural yield (46.5%) was obtained at 210 °C for 20 min. It was found that the physical barrier of lignin was its mainly inhibition mechanism that limited the enzymatic digestibility of H2SO4 pretreated solid. The following NaOH pretreatment removed 90.8% of lignin and resulted in excellent glucan enzymatic conversion (98.6%). A large amount of acid insoluble lignin (AIL, 17.0 g/100 g CS), p-coumaric acid (1416.9 mg/100 g CS) and ferulic acid (249.4 mg/100 g CS) were observed in NaOH pretreatment liquor. The two-step pretreated CS produced up to 115.3 g/L of ethanol during simultaneous saccharification and fermentation (SSF) at 25% (w/w) solid loading. These results demonstrated that the successive H2SO4 and NaOH pretreatment was an efficient method for fractionation and integrative utilization of CS.