VTT Technical Research Centre of Finland, PO Box 1000, 02044 VTT, Finland.
Biotechnol Bioeng. 2011 Dec;108(12):2823-34. doi: 10.1002/bit.23242. Epub 2011 Jun 30.
Lignin-derived inhibition is a major obstacle restricting the enzymatic hydrolysis of cell wall polysaccharides especially with softwood lignocellulosics. Enzyme adsorption on lignin is suggested to contribute to the inhibitory effect of lignin. The interaction of cellulases with softwood lignin was studied in the present work with commercial Trichoderma reesei cellulases (Celluclast) and lignin-rich residues isolated from steam pretreated softwood (SPS) by enzymatic and acid hydrolysis. Both lignin preparations inhibited the hydrolysis of microcrystalline cellulose (Avicel) and adsorbed the major cellulases present in the commercial cellulase mixture. The adsorption phenomenon was studied at low temperature (4°C) and at the typical hydrolysis temperature (45°C) by following activities of free and lignin-bound enzymes. Severe inactivation of the lignin-bound enzymes was observed at 45°C, however at 4°C the enzymes retained well their activity. Furthermore, SDS-PAGE analysis of the lignin-bound enzymes indicated that very strong interactions form between the residue and the enzymes at 45°C, because the enzymes were not released from the residue in the electrophoresis. These results suggest that heat-induced denaturation may take place on the surface of softwood lignin at the hydrolysis temperature.
木质素衍生的抑制作用是限制细胞壁多糖酶解的主要障碍，尤其是对软木木质纤维素。酶吸附在木质素上被认为有助于木质素的抑制作用。本工作研究了纤维素酶与软木木质素的相互作用，所用木质素来自蒸汽预处理软木（SPS）的酶解和酸解富木质素残余物，以及商业里氏木霉纤维素酶（Celluclast）。两种木质素制剂均抑制微晶纤维素（Avicel）的水解，并吸附商业纤维素酶混合物中存在的主要纤维素酶。通过跟踪游离酶和木质素结合酶的活性，在低温（4°C）和典型水解温度（45°C）下研究了吸附现象。在 45°C 时，木质素结合酶严重失活，但在 4°C 时，酶仍能很好地保持其活性。此外，木质素结合酶的 SDS-PAGE 分析表明，在 45°C 时，残留物与酶之间形成了非常强的相互作用，因为在电泳过程中酶没有从残留物中释放出来。这些结果表明，在水解温度下，木质素表面可能发生热诱导变性。
