亚硫酸盐预处理对棉秆酶水解的影响

为了提高棉秆的酶水解效率，研究了棉秆亚硫酸盐预处理过程中亚硫酸氢钠用量、浓硫酸用量、预处理温度与时间对预处理效果的影响，同时比较了棉秆不同部位的亚硫酸盐预处理效果。结果表明：预处理时添加亚硫酸氢钠可提高棉秆酶水解效率，随着用量的增加，底物酶水解转化率升高，用量超过8%后基本不变；预处理液pH值可影响棉秆亚硫酸盐预处理效果，存在一个最佳pH值，研究中预处理液pH值为2.65时，底物的酶水解转化率最高；当预处理温度由100℃升高至170℃时，底物酶水解转化率升高较少，但当预处理温度继续升高时，底物酶水解转化率明显升高，在预处理温度180℃并保温20 min时底物酶水解转化率达到最高为70.10%，继续延长保温时间底物酶水解转化率无明显变化。亚硫酸盐预处理过程中，木素和戊聚糖不断从原料中溶出，有利于后续的酶水解，研究发现木素的溶出比戊聚糖的溶出对棉秆酶水解的影响更大。棉秆不同部位的亚硫酸盐预处理效果不同，酶水解从易到难的顺序是：棉秆皮>细枝>全棉秆>主干>棉秆芯。

Effect of sulfite pretreatment on enzymatic hydrolysis of cotton stalk

In order to improve enzymatic hydrolysis efficiency, sulfite pretreatment (SPORL) of cotton stalk was investigated. Added amount of sodium bisulfite, pH value, temperature and time had great effects on cotton stalk saccharification. Cellulose conversion ratio increased with the addition of sodium bisulfite, and levelled off after 8% sodium bisulfite dose. There was an optimal pH value in sulfite pretreatment of cotton stalk. In this study, cellulose conversion ratio reached maximum at pH value 2.65. Before 170℃, the change of enzymatic hydrolysis was not remarkable. After then, enzymatic hydrolysis increased quickly and cellulose conversion ratio got to 70.10% at 180℃ for 20 min. Prolonging holding time was no longer effective. During sulfite pretreatment, both lignin and pentosan were dissolved from cotton stalk in the meantime, which could help cellulose enzymatic hydrolysis. The dissolution of lignin was more effective on cellulose enzymatic hydrolysis than dissolution of pentosan. This study also indicated that the cotton bast was easier to enzymatically hydrolyze than the whole cotton stalk and the cotton xylem was more difficult than the whole cotton stalk in the same conditions of sulfite pretreatment.