Laboratory of Sustainable and Catalytic Processing, Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
Nat Chem. 2018 Dec;10(12):1222-1228. doi: 10.1038/s41557-018-0134-4. Epub 2018 Sep 17.
Polysaccharide depolymerization is an essential step for valorizing lignocellulosic biomass. In inexpensive systems such as pure water or dilute acid mixtures, carbohydrate monomer degradation rates exceed hemicellulose-and especially cellulose-depolymerization rates at most easily accessible temperatures, limiting sugar yields. Here, we use a reversible stabilization of xylose and glucose by acetal formation with formaldehyde to alter this kinetic paradigm, preventing sugar dehydration to furans and their subsequent degradation. During a harsh organosolv pretreatment in the presence of formaldehyde, over 90% of xylan in beech wood was recovered as diformylxylose (compared to 16% xylose recovery without formaldehyde). The subsequent depolymerization of cellulose led to carbohydrate yields over 70% and a final concentration of ~5 wt%, whereas the same conditions without formaldehyde gave a yield of 28%. This stabilization strategy pushes back the longstanding kinetic limits of polysaccharide depolymerization and enables the recovery of biomass-derived carbohydrates in high yields and concentrations.
多糖解聚是木质纤维素生物质增值利用的关键步骤。在纯水或稀酸混合物等廉价体系中，碳水化合物单体的降解速率在大多数易于达到的温度下超过了半纤维素——特别是纤维素的解聚速率，从而限制了糖的得率。在这里，我们通过与甲醛形成缩醛来可逆稳定木糖和葡萄糖，从而改变这种动力学模式，防止糖脱水生成呋喃及其随后的降解。在有甲醛存在的苛刻的有机溶剂预处理过程中，山毛榉木中的超过 90%的木聚糖被回收为二糠醛基木糖（与没有甲醛的情况下 16%的木糖回收率相比）。随后的纤维素解聚导致碳水化合物的收率超过 70%，最终浓度约为 5wt%，而没有甲醛的相同条件下的收率为 28%。这种稳定策略推迟了多糖解聚的长期动力学限制，并能够以高产率和高浓度回收生物质衍生的碳水化合物。
