对甘蔗渣有机酸预处理、碱处理和氧化预处理过程中得到的5种木质素[乙酸木质素(AAL)、Acetosolv木质素(AsL)、Milox木质素(ML)、过氧乙酸木质素(PAAL)和碱木质素(AL)]进行了结构表征，通过元素、官能团和化学组分分析、分子量测定及光谱特性分析，验证了甘蔗渣木质素为典型的H?S?G型木质素，除PAAL外其余4种木质素具有类似的结构特性，而PAAL由于过氧乙酸的氧化作用使木质素结构显著变化，从而具有较低的分子量、较高的酸溶木质素和羰基含量. 将5种木质素添加至纤维素酶催化水解体系中，纤维素转化率均有不同程度降低，PAAL的抑制作用最强. 结合添加木质素单体模型化合物的实验表明，酚羟基是木质素抑制纤维素酶作用的关键官能团，对羟苯基中酚羟基的抑制作用比愈创木基和紫丁香基更强. 木质素对纤维素酶解的抑制作用不只是通过无效吸附纤维素酶实现，小分子的酚类降解产物也会降低纤维素的酶解转化效率.
Five types of lignin by-products were isolated from sugarcane bagasse by organic acid, alkaline and oxidative pretreatments, respectively, namely acetic acid lignin (AAL), acetosolve lignin (AsL), milox lignin (ML), peracetic acid lignin (PAAL) and alkaline lignin (AL). Structure characterizations were performed by analysis of elements, functional groups, chemical components, molecular weights and spectra. The results confirmed that sugarcane bagasse lignin was a typical H?G?S lignin. Except PAAL lignin, other four isolated lignins showed similar structures. PAAL lignin had lower molecular weight, higher carbonyl and acid-soluble lignin contents. Inhibition of cellulose conversion were observed when addition of these five lignins individually into the system of enzymatic hydrolysis of cellulose, and PAAL showed the highest inhibitive action. Further experiments by addition of lignin model compounds in to the system indicated that phenolic hydroxyl group (Ph-OH) was a key functional group mediating the inhibition of cellulose conversion by lignin, and the inhibitive effect of Ph-OH in p-hydroxyphenyl (H) was stronger than those in guaiacyl and syringyl structures. The finding of this work demonstrated that the inhibitive action of lignin to enzymatic hydrolysis of cellulose was not only attributed to non-productive adsorption of enzymes, but also to the inhibition of small-molecule phenol compounds yielded by deplymerization of lignin during the pretreatment.
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