两种木质素对纤维素酶水解的影响机制

摘要

为探究木质素对纤维素酶水解效率的影响,将苦竹中提取的乙醇木质素(EOL-B)和磨木木质素(MWL-B)作为模型物添加到微晶纤维素中进行酶吸附和水解.结果表明:添加8 g/L MWL-B使得反应72 h的葡萄糖得率从51.34%降低到46.06%;添加8 g/L EOL-B使得反应72 h葡萄糖得率从51.34%增加到61.06%.与MWL-B相比,EOL-B与纤维素酶蛋白之间亲和力和结合力较低,故纤维素酶在EOL-B上的非特异吸附更少.FT-IR和13C NMR分析表明:经乙醇处理后,木质素分子中C—C凝缩单元减少,β-O-4′键断裂,导致木质素分子的亲水性增加,阻断了与纤维素酶蛋白疏水性氨基酸的结合,对纤维素酶蛋白吸附量减少,从而使得纤维底物周围的酶蛋白浓度增加,水解率提高.%In order to investigate the effect of lignin on the enzymatic hydrolysis of cellulose, the ethanol organosolv lignins (EOL-B)and milled wood lignin(MWL-B)were extracted from bitter bamboo and added to the microcrystalline cellulose for enzymatic digestibility and adsorption.The results showed that the addition of MWL-B(8 g/L)decreased the 72 h hydrolysis yields of glucose from 51.34%to 46.06%.But the addition of EOL-B(8 g/L)significantly improved the 72 h hydrolysis yields of glucose from 51.34%to 61.06%.Langmuir adsorption isotherms showed that EOL-B had lower binding ability and maximum adsorption capacity to the cellulase enzymes than MWL-B,which led to less non-productive binding.And FT-IR and 13C NMR spectra showed that the condensed structure of C—C of lignin reduced and the β-O-4′linkages cracked in the ethanol organosolv process,which resulted in increasing the hydrophilicity of lignin,blocking the combination of lignin and the hydrophobic amino acid of cellulose,decreasing the adsorption of cellulose,increasing the cellulose concentration around the cellulose substrate and promoting the effect of enzymatic hydrolysis.