Khatri Vinay, Meddeb-Mouelhi Fatma, Adjallé Kokou, Barnabé Simon, Beauregard Marc
1Centre de recherche sur les matériaux lignocellulosiques, Université du Québec à Trois-Rivières, C.P. 500, Trois-Rivières, QC G9A 5H7 Canada.
2PROTEO, Université Laval, Québec, QC G1V 4G2 Canada.
Biotechnol Biofuels. 2018 May 18;11:144. doi: 10.1186/s13068-018-1145-5. eCollection 2018.
Pretreatment of lignocellulosic biomass (LCB) is a key step for its efficient bioconversion into ethanol. Determining the best pretreatment and its parameters requires monitoring its impacts on the biomass material. Here, we used fluorescent protein-tagged carbohydrate-binding modules method (FTCM)-depletion assay to study the relationship between surface-exposed polysaccharides and enzymatic hydrolysis of LCB.
Our results indicated that alkali extrusion pretreatment led to the highest hydrolysis rates for alfalfa stover, cattail stems and flax shives, despite its lower lignin removal efficiency compared to alkali pretreatment. Corn crop residues were more sensitive to alkali pretreatments, leading to higher hydrolysis rates. A clear relationship was consistently observed between total surface-exposed cellulose detected by the FTCM-depletion assay and biomass enzymatic hydrolysis. Comparison of bioconversion yield and total composition analysis (by NREL/TP-510-42618) of LCB prior to or after pretreatments did not show any close relationship. Lignin removal efficiency and total cellulose content (by NREL/TP-510-42618) led to an unreliable prediction of enzymatic polysaccharide hydrolysis.
Fluorescent protein-tagged carbohydrate-binding modules method (FTCM)-depletion assay provided direct evidence that cellulose exposure is the key determinant of hydrolysis yield. The clear and robust relationships that were observed between the cellulose accessibility by FTCM probes and enzymatic hydrolysis rates change could be evolved into a powerful prediction tool that might help develop optimal biomass pretreatment strategies for biofuel production.
木质纤维素生物质（LCB）的预处理是将其高效生物转化为乙醇的关键步骤。确定最佳预处理方法及其参数需要监测其对生物质材料的影响。在此，我们使用荧光蛋白标记的碳水化合物结合模块方法（FTCM）-消耗测定法来研究表面暴露的多糖与LCB酶解之间的关系。
我们的结果表明，碱挤压预处理对苜蓿秸秆、香蒲茎和亚麻屑产生了最高的水解率，尽管与碱预处理相比其木质素去除效率较低。玉米作物残渣对碱预处理更敏感，导致更高的水解率。通过FTCM-消耗测定法检测到的总表面暴露纤维素与生物质酶解之间始终存在明显的关系。预处理前后LCB的生物转化产率和总成分分析（通过NREL/TP-510-42618）的比较未显示出任何密切关系。木质素去除效率和总纤维素含量（通过NREL/TP-510-42618）导致对酶促多糖水解的预测不可靠。
荧光蛋白标记的碳水化合物结合模块方法（FTCM）-消耗测定法提供了直接证据，表明纤维素暴露是水解产率的关键决定因素。FTCM探针检测到的纤维素可及性与酶解速率变化之间观察到的清晰而稳健的关系可以演变成一种强大的预测工具，这可能有助于开发用于生物燃料生产的最佳生物质预处理策略。
