An integrated wet-milling and alkali pretreatment was applied to corn stover prior to enzymatic hydrolysis. The effects of NaOH concentration in the pretreatment on crystalline structure, chemical composition, and reducing-sugar yield of corn stover were investigated, and the mechanism of increasing reducing-sugar yield by the pretreatment was discussed. The experimental results showed that the crystalline structure of corn stover was disrupted, and lignin was removed, while cellulose and hemicellulose were retained in corn stover by the pretreatment with 1% NaOH in 1 h. The reducing-sugar yield from the pretreated corn stovers increased from 20.2% to 46.7% when the NaOH concentration increased from 0% to 1%. The 1% NaOH pretreated corn stover had a holocellulose conversion of 55.1%. The increase in reducing-sugar yield was related to the crystalline structure disruption and delignification of corn stover. It was clarified that the pretreatment significantly enhanced the conversion of cellulose and hemicellulose in the corn stover to sugars.

Cellulase and xylanase from Trichoderma reesei were immobilized simultaneously on Eudragit L-100, a reversibly soluble polymer. The effects of polymer concentration and polymer precipitation pH on enzyme activity recovery were investigated at an enzyme complex concentration of 1%. The immobilization mechanism of cellulase and xylanase on the polymer was discussed. An activity recovery of 75% and 59% was obtained for the cellulase and the xylanase, respectively, under the condition of a polymer concentration at 2% and a polymer precipitation pH at 4.0. Most zymoproteins might be connected to the polymer by electrostatic attraction in a medium of pH 4.8. In addition, the covalent coupling between the zymoproteins and the polymer was demonstrated by the infrared spectrograms. It was suggested that dehydration-condensation reaction occurred between the zymoproteins and the polymer during the immobilization.

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