LAUSR

In this study, we determined the effect of organosolv pretreatment on herbaceous biomasses corn stover and wheat straw, by using high-concentration ethanol as the solvent. A high-concentration of ethanol allows for the easy reuse and recycling of the solvent. First, we tested the effects of ethanol pretreatments at 60 and 99.5% (w/w) and found that highest solvent concentration resulted in low glucose digestibility. The maximum enzymatic glucose digestibility with 60% ethanol was 92.6% at 190°C for 120 min (using corn stover) and 86.9% at 190°C for 120 min (using wheat straw). In contrast, the digestion rates with 99.5% ethanol were 68.8 and 77.4% under the same conditions, respectively, indicating that there is a limit to the use of high-concentration ethanol as the solvent. To overcome this limitation, we applied a mechanical pretreatment step before the chemical pretreatment. Subsequently, glucose digestibility increased significantly to 93.1% with 99.5% ethanol as the solvent. Additionally the enzymatic digestibility of mechanically pretreated corn stover was higher than that of non-pretreated corn stover by about 40%. Taken together, these results confirm the efficacy of using high-concentration ethanol as a solvent for organosolv pretreatment when done in conjunction with mechanical pretreatment.