Sun Fubao Fuelbiol, Zhao Xiaoqin, Hong Jiapeng, Tang Yanjun, Wang Liang, Sun Haiyan, Li Xiang, Hu Jinguang
Key Laboratory of Industrial Biotechnology, School of Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122 China.
Key Laboratory of Industrial Biotechnology, School of Biotechnology, Ministry of Education, Jiangnan University, Wuxi, 214122 China ; State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, 510640 China.
Biotechnol Biofuels. 2016 Mar 11;9:59. doi: 10.1186/s13068-016-0472-7. eCollection 2016.
Previous work has demonstrated that glycerol organosolv pretreatment can effectively improve the hydrolyzability of various lignocellulosic substrates. This pretreatment process strategy is ideal to integrate a commercially successful lignocellulosic and vegetable oil biorefinery industry. However, industrially relevant high-solid-loading hydrolyzability and fermentability of the pretreated substrates have yet to be considered for enzyme-based lignocellulosic biorefineries.
In this study, an AGO pretreatment of sugarcane bagasse was evaluated with regard to the component selectivity, structural modification, hydrolyzability, and fermentation of pretreated substrates. The results showed that the AGO pretreatment presented good component selectivity, removing approximately 70 % lignin and hemicellulose, respectively, from sugarcane bagasse with a near-intact preservation (94 %) of the overall cellulose. The pretreatment deconstructed the recalcitrant architecture of natural lignocellulosic biomass, thereby modifying the structure at the macro-/micrometer level (fiber size, surface area, average size, roughness) and supermolecular level (key chemical bond dissociation) of lignocellulosic substrates towards good hydrolyzability. Notably, extraordinarily few fermentation inhibitors (<0.2 g furfural and 5-hydromethyl furfural/kg feedstock) were generated from the AGO pretreatment process, which was apparently due to the prominent role of glycerol organic solvent in protecting monosaccharides against further degradation. The 72-h enzymatic hydrolysis of pretreated substrates at 15 % solid content achieved 90 % completion with Cellic CTec2 at 10 FPU/g dried substrate. With a simple nutrition (only 10 g/L (NH4)2SO4) addition, the fed-batch semi-SSF of AGO-pretreated substrates (30 % solid content) almost reached 50 g/L ethanol with cellulase preparation at 10 FPU/g dried substrate. These results have revealed that the pretreated substrate is susceptible and accessible to cellulase enzymes, thereafter exhibiting remarkable hydrolyzability and fermentability.
The AGO pretreatment is a promising candidate for the current pretreatment process towards industrially relevant enzyme-based lignocellulosic biorefineries.
先前的研究表明，甘油有机溶剂预处理能够有效提高各种木质纤维素底物的水解性能。这种预处理工艺策略对于整合商业上成功的木质纤维素和植物油生物精炼产业而言是理想的。然而，基于酶的木质纤维素生物精炼厂尚未考虑预处理底物在工业相关高固含量下的水解性能和发酵性能。
在本研究中，对甘蔗渣的AGO预处理在预处理底物的成分选择性、结构修饰、水解性能和发酵性能方面进行了评估。结果表明，AGO预处理具有良好的成分选择性，分别从甘蔗渣中去除了约70%的木质素和半纤维素，同时整体纤维素的保留率接近完整（94%）。该预处理解构了天然木质纤维素生物质的顽固结构，从而在木质纤维素底物的宏观/微米尺度（纤维尺寸、表面积、平均尺寸、粗糙度）和超分子尺度（关键化学键解离）上对结构进行修饰，以实现良好的水解性能。值得注意的是，AGO预处理过程中产生的发酵抑制剂极少（糠醛和5-羟甲基糠醛均<0.2 g/kg原料），这显然是由于甘油有机溶剂在保护单糖不被进一步降解方面发挥了重要作用。在15%固含量下对预处理底物进行72小时的酶水解，使用Cellic CTec2酶在10 FPU/g干底物的用量下完成率达到90%。通过简单添加营养物质（仅10 g/L硫酸铵），对AGO预处理底物（30%固含量）进行补料分批半固态发酵，使用纤维素酶制剂在10 FPU/g干底物的用量下，乙醇产量几乎达到50 g/L。这些结果表明，预处理后的底物对纤维素酶敏感且易于被作用，进而表现出显著的水解性能和发酵性能。
对于当前面向工业相关的基于酶的木质纤维素生物精炼厂的预处理工艺而言，AGO预处理是一个有前景的选择。
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