Design of a highly thermostable hemicellulose-degrading blend from Thermotoga neapolitana for the treatment of lignocellulosic biomass
Design of a highly thermostable hemicellulose-degrading blend from Thermotoga neapolitana for the treatment of lignocellulosic biomass
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DOI：
10.1016/j.jbiotec.2019.03.005
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发表时间：
2019-04-20
影响因子：
4.1
通讯作者：
Dall'Osto, Luca
中科院分区：
文献类型：
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作者：
Benedetti, Manuel;Vecchi, Valeria;Dall'Osto, Luca
木质纤维素生物转化为可发酵糖是利用植物生物质可持续生产生物燃料的关键过程。植物原料中的多糖可以使用热稳定的酶混合物来降解细胞壁，从而避免有害且昂贵的预处理。嗜热菌门的（超）嗜热细菌为此类工业应用提供了丰富的酶来源。在这里，我们选择 T. neapolitana 作为超嗜热半纤维素酶的来源，用于降解木质纤维素生物质。从 T. neapolitana 基因组 DNA 中克隆了两个编码推定半纤维素酶的基因，并在大肠杆菌中表达。进一步的表征表明，这些基因编码内切 1,4-ss 半乳聚糖酶和 a-L-阿拉伯呋喃糖苷酶，其最佳温度为（相似）90 摄氏度，催化过程中的周转数很高（在可溶性底物上，kcat 值分别为（相似）177 和（相似）133 s(-1)）。这些酶与另外三种那不勒斯 T. neapolitana 超嗜热半纤维素酶 - 内切 1,4-β-木聚糖酶 (XynA)、内切-1,4-β-甘露聚糖酶 (ManB/Man5A) 和 β-葡萄糖苷酶 (GghA) 组合，形成高度热稳定的半纤维素分解混合物。用这种酶混合物处理大麦秆和玉米麸可以溶解多种半纤维素，并且当复杂的底物被纤维素酶进一步降解时，可发酵糖的产量提高高达 65%。
The biological conversion of lignocellulose into fermentable sugars is a key process for the sustainable production of biofuels from plant biomass. Polysaccharides in plant feedstock can be valorized using thermostable mixtures of enzymes that degrade the cell walls, thus avoiding harmful and expensive pre-treatments. (Hyper) thermophilic bacteria of the phylum Thermotogae provide a rich source of enzymes for such industrial applications. Here we selected T. neapolitana as a source of hyperthermophilic hemicellulases for the degradation of lignocellulosic biomass. Two genes encoding putative hemicellulases were cloned from T. neapolitana genomic DNA and expressed in Escherichia coli. Further characterization revealed that the genes encoded an endo-1,4-ss galactanase and an a-L-arabinofuranosidase with optimal temperatures of (similar to)90 degrees C and high turnover numbers during catalysis (kcat values of (similar to)177 and (similar to)133 s(-1), respectively, on soluble substrates). These enzymes were combined with three additional T. neapolitana hyperthermophilic hemicellulases -endo-1,4-beta-xylanase (XynA), endo-1,4-beta-mannanase (ManB/Man5A) and beta-glucosidase (GghA) -to form a highly thermostable hemicellulolytic blend. The treatment of barley straw and corn bran with this enzymatic cocktail resulted in the solubilization of multiple hemicelluloses and boosted the yield of fermentable sugars by up to 65% when the complex substrates were further degraded by cellulases.