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Abstract：
BACKGROUND: Microbial expansins (EXLXs) are non-lytic proteins homologous to plant expansins involved in plant cell wall formation. Due to their non-lytic cell wall loosening properties and potential to disaggregate cellulosic structures, there is considerable interest in exploring the ability of microbial expansins (EXLX) to assist the processing of cellulosic biomass for broader biotechnological applications. Herein, EXLXs with different modular structure and from diverse phylogenetic origin were compared in terms of ability to bind cellulosic, xylosic, and chitinous substrates, to structurally modify cellulosic fibrils, and to boost enzymatic deconstruction of hardwood pulp.
RESULTS: Five heterogeneously produced EXLXs (Clavibacter michiganensis; CmiEXLX2, Dickeya aquatica; DaqEXLX1, Xanthomonas sacchari; XsaEXLX1, Nothophytophthora sp.; NspEXLX1 and Phytophthora cactorum; PcaEXLX1) were shown to bind xylan and hardwood pulp at pH 5.5 and CmiEXLX2 (harboring a family-2 carbohydrate-binding module) also bound well to crystalline cellulose. Small-angle X-ray scattering revealed a 20-25% increase in interfibrillar distance between neighboring cellulose microfibrils following treatment with CmiEXLX2, DaqEXLX1, or NspEXLX1. Correspondingly, combining xylanase with CmiEXLX2 and DaqEXLX1 increased product yield from hardwood pulp by ~ 25%, while supplementing the TrAA9A LPMO from Trichoderma reesei with CmiEXLX2, DaqEXLX1, and NspEXLX1 increased total product yield by over 35%.
CONCLUSIONS: This direct comparison of diverse EXLXs revealed consistent impacts on interfibrillar spacing of cellulose microfibers and performance of carbohydrate-active enzymes predicted to act on fiber surfaces. These findings uncover new possibilities to employ EXLXs in the creation of value-added materials from cellulosic biomass.
RESULTS: Five heterogeneously produced EXLXs (Clavibacter michiganensis; CmiEXLX2, Dickeya aquatica; DaqEXLX1, Xanthomonas sacchari; XsaEXLX1, Nothophytophthora sp.; NspEXLX1 and Phytophthora cactorum; PcaEXLX1) were shown to bind xylan and hardwood pulp at pH 5.5 and CmiEXLX2 (harboring a family-2 carbohydrate-binding module) also bound well to crystalline cellulose. Small-angle X-ray scattering revealed a 20-25% increase in interfibrillar distance between neighboring cellulose microfibrils following treatment with CmiEXLX2, DaqEXLX1, or NspEXLX1. Correspondingly, combining xylanase with CmiEXLX2 and DaqEXLX1 increased product yield from hardwood pulp by ~ 25%, while supplementing the TrAA9A LPMO from Trichoderma reesei with CmiEXLX2, DaqEXLX1, and NspEXLX1 increased total product yield by over 35%.
CONCLUSIONS: This direct comparison of diverse EXLXs revealed consistent impacts on interfibrillar spacing of cellulose microfibers and performance of carbohydrate-active enzymes predicted to act on fiber surfaces. These findings uncover new possibilities to employ EXLXs in the creation of value-added materials from cellulosic biomass.
摘要：
背景：微生物膨胀蛋白（EXLXs）是与参与植物细胞壁形成的植物膨胀蛋白同源的非裂解蛋白。由于其非裂解细胞壁松动特性和潜在的解聚纤维素结构，人们对探索微生物膨胀蛋白(EXLX)协助纤维素生物质加工以用于更广泛的生物技术应用的能力有相当大的兴趣。在这里，在结合纤维素的能力方面，比较了具有不同模块化结构和不同系统发育起源的EXLX，纤维素，和几丁质底物，在结构上修饰纤维素原纤维，并促进硬木纸浆的酶解构。
结果：五种异源生产的EXLXs（密根氏杆菌；CmiEXLX2，水牙树；DaqEXLX1，糖质黄单胞菌；XsaEXLX1，无植物。；NspEXLX1和疫霉；PcaEXLX1）被证明在pH5.5时与木聚糖和硬木纸浆结合，CmiEXLX2（带有2家族碳水化合物结合模块）也与结晶纤维素结合良好。小角度X射线散射显示，用CmiEXLX2，DaqEXLX1或NspEXLX1处理后，相邻纤维素微纤丝之间的纤丝间距离增加了20-25％。相应地,将木聚糖酶与CmiEXLX2和DaqEXLX1相结合，可将硬木纸浆的产品产量提高约25％，在用CmiEXLX2、DaqEXLX1和NspEXLX1补充来自里氏木霉的TrAA9ALPMO的同时,产品总收率提高了35%以上。
结论：这种不同EXLXs的直接比较揭示了对纤维素微纤维的原纤间距和预测作用于纤维表面的碳水化合物活性酶的性能的一致影响。这些发现揭示了使用EXLXs从纤维素生物质创建增值材料的新可能性。
结果：五种异源生产的EXLXs（密根氏杆菌；CmiEXLX2，水牙树；DaqEXLX1，糖质黄单胞菌；XsaEXLX1，无植物。；NspEXLX1和疫霉；PcaEXLX1）被证明在pH5.5时与木聚糖和硬木纸浆结合，CmiEXLX2（带有2家族碳水化合物结合模块）也与结晶纤维素结合良好。小角度X射线散射显示，用CmiEXLX2，DaqEXLX1或NspEXLX1处理后，相邻纤维素微纤丝之间的纤丝间距离增加了20-25％。相应地,将木聚糖酶与CmiEXLX2和DaqEXLX1相结合，可将硬木纸浆的产品产量提高约25％，在用CmiEXLX2、DaqEXLX1和NspEXLX1补充来自里氏木霉的TrAA9ALPMO的同时,产品总收率提高了35%以上。
结论：这种不同EXLXs的直接比较揭示了对纤维素微纤维的原纤间距和预测作用于纤维表面的碳水化合物活性酶的性能的一致影响。这些发现揭示了使用EXLXs从纤维素生物质创建增值材料的新可能性。
