两步法预处理脱除木质素对杨木酶水解的影响

Effects of Removal of Lignin via Two-stage Pretreatment on the Enzymatic Hydrolysis of Poplar

以杨木片为原料,采用两步法预处理脱除木质素后,对原料进行酶水解,对杨木表观结构、理化特征及酶水解结果进行考察。实验结果显示:相较于一步法蒸汽爆破(SE)预处理,碱性磺化-蒸汽爆破(AS-SE)和碱性氧化-蒸汽爆破(AO-SE)预处理后均可脱除50%左右的木质素,并且显著增加了物料中的酸性亲水基团如磺酸基和羧酸基含量,纤维素可及度分别提高至132.04和119.10mg/g。傅里叶红外光谱(FT-IR)结果表明碱性磺化和碱性氧化后,木质素结构中出现了亲水性功能基团(羟基、羧基和磺酸基),扫描电镜(SEM)结果表明两步法预处理后的物料表面出现开裂分层、层层剥落的现象。AS-SE预处理后,杨木纤维素酶水解率高达81.09%,原料糖得率达到73.72%。两步法预处理可对木质素进行选择性脱除和改性,改变了木质素理化特性及表观结构,增强了纤维素酶水解效果。

The effects of lignin fractionation via two-stage pretreatment on the surface morphology, physicochemical properties and enzymatic hydrolysis of the poplar chips were investigated. The results showed that, comparing to one-stage steam explosion(SE) pretreatment, alkaline sulfonation-steam explosion(AS-SE) and alkaline oxidation-steam explosion(AO-SE) pretreatment both led to the removal of around 50% lignin from biomass, while incorporating extensive hydrophilic acid groups including sulfonic and carboxylic groups into substrates. As a result, cellulose accessibility was increased to 132. 04 and 119. 10 mg/ g, respectively. Besides, FT-IR spectrum confirmed the incorporation of hydroxyl, carboxylic and sulfonic groups into lignin after AS and AO pretreatments. SEM images showed the cracked and corroded surface morphology after the two-stage pretreatments for lignin fractionation. After the AS-SE pretreatment, 81. 09% of the cellulose in pretreated solid could be converted to glucose, while the yield of biomass saccharification was improved to 73. 72%. These results indicated that lignin fractionation via two-stage pretreatment led to the selectively removal and modification of lignin, resulting in the change of the physicochemical properties and surface morphology of lignin, and favoring the enzymatic hydrolysis of cellulose.