Pentari Christina, Katsimpouras Constantinos, Haon Mireille, Berrin Jean-Guy, Zerva Anastasia, Topakas Evangelos
Industrial Biotechnology & Biocatalysis Group, School of Chemical Engineering, National Technical University of Athens, 9 Iroon Polytechniou Str., Zografou Campus, 15772, Athens, Greece.
Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, 02139 MA, USA.
Biotechnol Biofuels Bioprod. 2025 Mar 26;18(1):38. doi: 10.1186/s13068-025-02639-0.
Lignin-carbohydrate complexes in lignocellulosic biomass act as a barrier to its biodegradation and biotechnological exploitation. Enzymatic dissociation between lignin and hemicellulose is a key process that allows the efficient bioconversion of both polymers. Glucuronoyl esterases of the Carbohydrate Esterase 15 family target the ester linkages between the glucuronic acid of xylan and lignin moieties, assisting enzymatic biodegradation of lignocellulose.
In this study, two CE15 glucuronoyl esterases from the white-rot fungi Artolenzites elegans and Trametes ljubarskyi were heterologously expressed in Pichia pastoris and biochemically characterized on the model substrate D-glucuronic acid ester with cinnamyl alcohol and a variety of pretreated lignocellulosic biomasses. The pretreatment method was shown to be a determining factor in revealing both the activity of the esterases on lignocellulose and their synergistic relationships with other hemicellulases. AeGE15 and TlGE15 demonstrated activity on pretreated biomass with high hemicellulose and lignin content, increasing saccharification by 57 ± 1 μM and 61 ± 3 μM of xylose equivalents, respectively. Furthermore, the synergy between these CE15 esterases and three xylanases from distinct glycoside hydrolase families (GH10, GH11 and GH30) was investigated on pretreated lignocellulosic samples, highlighting beneficial enzymatic interplays. Pretreated birchwood degradation by AnXyn11 was increased from 6% to approximately 10% by the esterases, based on xylose equivalents of unsubstituted xylooligomers. The GEs also promoted the glucuronoxylanase specificity of TtXyn30A, leading up to three-times higher release in aldouronic acids. Finally, a synergistic effect between AeGE15 and TmXyn10 was observed on pretreated corn bran, increasing xylose and xylotriose release by 27 ± 8% and 55 ± 15%, respectively.
Both CE15 esterases promoted biomass saccharification by the xylanases, while there was a prominent effect on the GH30 glucuronoxylanase regarding the release of aldouronic acids. Overall, this study shed some light on the role of CE15 glucuronoyl esterases in the enzymatic biodegradation of plant biomass, particularly its (arabino)glucuronoxylan component, during cooperative activity with xylanases.
木质纤维素生物质中的木质素 - 碳水化合物复合物对其生物降解和生物技术开发构成障碍。木质素与半纤维素之间的酶促解离是实现这两种聚合物高效生物转化的关键过程。碳水化合物酯酶15家族的葡糖醛酸酯酶作用于木聚糖的葡糖醛酸与木质素部分之间的酯键，有助于木质纤维素的酶促生物降解。
在本研究中，来自白腐真菌秀丽阿太菌和柳巴尔斯基栓菌的两种CE15葡糖醛酸酯酶在毕赤酵母中进行了异源表达，并以肉桂醇和各种预处理的木质纤维素生物质为模型底物进行了生化特性分析。结果表明，预处理方法是揭示酯酶在木质纤维素上的活性及其与其他半纤维素酶协同关系的决定性因素。AeGE15和TlGE15对预处理后具有高半纤维素和木质素含量的生物质表现出活性，分别使糖化增加了57±1 μM和61±3 μM木糖当量。此外，在预处理的木质纤维素样品上研究了这些CE15酯酶与来自不同糖苷水解酶家族（GH10、GH11和GH30）的三种木聚糖酶之间的协同作用，突出了有益的酶促相互作用。基于未取代木寡糖的木糖当量，酯酶使AnXyn11对预处理桦木的降解率从6%提高到约10%。这些葡糖醛酸酯酶还提高了TtXyn30A的葡糖醛酸木聚糖酶特异性，使醛糖酸释放量提高了三倍。最后，在预处理的玉米麸上观察到AeGE15和TmXyn10之间的协同作用，分别使木糖和木三糖释放量增加了27±8%和55±15%。
两种CE15酯酶均促进了木聚糖酶对生物质的糖化作用，同时在醛糖酸释放方面对GH30葡糖醛酸木聚糖酶有显著影响。总体而言，本研究揭示了CE15葡糖醛酸酯酶在与木聚糖酶协同作用期间对植物生物质酶促生物降解中的作用，特别是其（阿拉伯）葡糖醛酸木聚糖成分。
