Department of Microbiology &Immunology, The University of British Columbia, Vancouver, BC, V6T 1Z3 Canada.
Forest Products Biotechnology/Bioenergy Group, Faculty of Forestry, The University of British Columbia, 2424 Main Mall, Vancouver, BC, V6T 1Z4, Canada.
Sci Rep. 2017 Feb 7;7:42121. doi: 10.1038/srep42121.
The recalcitrance of woody biomass, particularly its lignin component, hinders its sustainable transformation to fuels and biomaterials. Although the recent discovery of several bacterial ligninases promises the development of novel biocatalysts, these enzymes have largely been characterized using model substrates: direct evidence for their action on biomass is lacking. Herein, we report the delignification of woody biomass by a small laccase (sLac) from Amycolatopsis sp. 75iv3. Incubation of steam-pretreated poplar (SPP) with sLac enhanced the release of acid-precipitable polymeric lignin (APPL) by 6-fold, and reduced the amount of acid-soluble lignin by ~15%. NMR spectrometry revealed that the APPL was significantly syringyl-enriched relative to the original material (16:1 vs. ~3:1), and that sLac preferentially oxidized syringyl units and altered interunit linkage distributions. sLac's substrate preference among monoaryls was also consistent with this observation. In addition, sLac treatment reduced the molar mass of the APPL by over 50%, as determined by gel-permeation chromatography coupled with multi-angle light scattering. Finally, sLac acted synergistically with a commercial cellulase cocktail to increase glucose production from SPP ~8%. Overall, this study establishes the lignolytic activity of sLac on woody biomass and highlights the biocatalytic potential of bacterial enzymes.
木质生物质，特别是其木质素成分的顽固性，阻碍了其向燃料和生物材料的可持续转化。尽管最近发现了几种细菌木质素酶，有望开发新型生物催化剂，但这些酶在很大程度上是使用模型底物进行表征的：缺乏它们在生物质上作用的直接证据。在此，我们报道了 Amycolatopsis sp. 75iv3 的一种小漆酶（sLac）对木质生物质的脱木质素作用。用 sLac 孵育蒸汽预处理的杨树（SPP）可将酸沉淀的聚合木质素（APPL）的释放量提高约 6 倍，并将酸溶性木质素的量减少约 15%。NMR 光谱表明，相对于原始材料，APPL 明显富含愈创木基（16:1 对3:1），并且 sLac 优先氧化愈创木基单元并改变单元间键合分布。sLac 对单芳基的底物偏好也与这一观察结果一致。此外，sLac 处理将 APPL 的摩尔质量降低了 50%以上，这是通过凝胶渗透色谱与多角度光散射联用确定的。最后，sLac 与商业纤维素酶混合物协同作用，将 SPP 的葡萄糖产量提高了约 8%。总的来说，这项研究确立了 sLac 对木质生物质的木质素降解活性，并强调了细菌酶的生物催化潜力。
